Skip to main content
NCBI home page
ACS AuthorChoice logoLink to ACS AuthorChoice
. 2023 Jan 26;62(5):2169–2180. doi: 10.1021/acs.inorgchem.2c03865

Structures, Thermal Properties, and Reactivities of Cationic Rh–cod Complexes in Solid State (cod = 1,5-Cyclooctadiene)

Ryo Sumitani †, Daisuke Kuwahara ‡, Tomoyuki Mochida †,§,*
PMCID: PMC9907349  PMID: 36701547

Abstract

graphic file with name ic2c03865_0011.jpg

Cationic rhodium complexes with 1,5-cyclooctadiene (cod) ligands are important organometallic compounds that are useful as precatalysts; however, their solid-state structures and thermal properties have not been adequately investigated. In this study, we synthesized [Rh(cod)L]X (L = cod, C6H6, PhMe; X = SbF6, (FSO2)2N (= FSA), CF3BF3, CB11H12) and investigated their phase behaviors, crystal structures, and reactivities. The phase transitions of these salts result in disordered solid-state structures. Moreover, the structural disorder increases with a decrease in the cation symmetry in the SbF6 salts; [Rh(cod)(PhMe)]SbF6 exhibits a rotator phase, and the cations in other salts exhibit a dynamic rotational disorder. In contrast, a lower crystal symmetry with less cation disorder is observed for FSA salts. The thermal stabilities and reactivities of these salts were further investigated. FSA salts with arene ligands produce anion-coordinated complexes upon melting, and SbF6 salts with arene ligands produce [Rh(cod)L′2]SbF6 (L′ = MeCN and SMe2) via an in situ single-crystal-to-single-crystal ligand-exchange reaction.

Short abstract

Salts of cationic [Rh(cod)L] complexes (L = cod, C6H6, PhMe) exhibit order−disorder phase transitions to result in dynamically disordered phases, including a rotator phase. Several salts undergo in situ ligand exchange via a single-crystal-to-single-crystal reaction.

Introduction

Cationic rhodium complexes with diene ligands such as 1,5-cyclooctadiene (cod) are important organometallic species that are useful for various catalytic applications, such as the hydrogenation of alkynes.1−5 Among them, [Rh(cod)2]+ serves as a precatalyst and can be used for the in situ generation of catalysts via ligand exchange. The catalytic activities of Rh–cod complexes are affected by the thermodynamics and kinetics of their ligand exchange reactions.6 In recent years, research on solid-state organic reactions has become increasingly important.7 Although solid-state properties of Rh–cod complexes are important for exploring solid-state organometallic reaction chemistry, this aspect has received little attention.8 In contrast, extensive solid-state research has been conducted on the chemistry of sandwich compounds such as ferrocene, cobaltocene, and their derivatives.9,10 Salts of cationic sandwich complexes, such as [Fe(C5H5)2]PF6, typically exhibit an ionic plastic crystal (IPC) phase because of the spherical shape of their cations.11−16 The constituent molecules undergo fast reorientation or rotation in the IPC phase, resulting in high crystal symmetry and ionic conductivity.17−29 Therefore, we hypothesized that salts of cationic Rh-cod complexes also exhibit an IPC or rotator phase. Molecules in the rotator phase typically rotate along the molecular long axis.30−33 Furthermore, [Rh(cod)2]+ and its derivatives readily undergo ligand exchange reactions in solution,34 although their solid-state reactivity has not been investigated. Crystalline phase reactions require structural flexibility or reaction cavities; hence, IPC or rotator phases may provide a suitable reaction medium for ligand exchange reactions.

The present study reports the structures, thermal properties, and reactivities of [Rh(cod)L]X (L = cod ([1]X), C6H6 ([2]X), PhMe ([3]X), X = SbF6, (FSO2)2N (= FSA), CF3BF3, CB11H12), and [Ir(cod)2]SbF6 ([1′]SbF6) in the solid state (Figure 1). Among these, [1]SbF6,35 [1′]SbF6,36 and [2]SbF65 are known compounds. Most of the anions are nearly spherical and are often used as components of IPCs, whereas the FSA anion (= (FSO2)2N–) is typically used for ionic liquids.37,38 First, we discuss the phase transitions and thermal decomposition behavior of [1]X, [2]X, and [3]X (X = SbF6, FSA). [1′]SbF6 and Rh–cod complexes with CF3BF3 and CB11H12 anions were also studied. These salts exhibit phase transitions that produce disordered structures in the solid state, of which [3]SbF6 exhibits a rotator phase at room temperature. The melting behavior of the FSA salts was investigated in detail. In addition, the cation dynamics of the SbF6 salts were investigated by solid-state NMR spectroscopy. Finally, we investigated the reactivity of SbF6 salts with arene ligands and observed that in situ ligand exchange occurs in ether via a single-crystal-to-single-crystal (SC–SC) reaction.

Figure 1.

Figure 1

Open in a new tab

Structural formulae of (a) cations and (b) anions used in this study.

Results and Discussion

Phase Behaviors

The phase behavior of [1]X–[3]X (X = SbF6, FSA, CF3BF3, and CB11H12) was investigated using differential scanning calorimetry (DSC). The phase sequences and DSC curves of the salts are shown in Figures 2 and S1, respectively. All the salts exhibit solid phase transitions, and the lowest temperature phase in each salt is designated as phase I. These salts decompose without melting at high temperatures, except for [1]FSA and [2]FSA, which melt at approximately 360 K.

Figure 2.

Figure 2

Open in a new tab

Phase sequences of [1]X–[3]X with (a) SbF6, (b) FSA, and (c) other anions. The phase transition temperature (K) and transition entropy (J mol–1 K–1) of each phase transition are shown above and below the bar charts, respectively. The liquid phases of [2]FSA and [3]FSA contain thermal reaction products (see text).

The phase sequences of the SbF6 salts are shown in Figure 2a. [1]SbF6 exhibits a phase transition at 329.9 K (ΔS = 19.6 J mol–1 K–1), and the corresponding Ir complex ([1′]SbF6) exhibits a phase transition at almost the same temperature (327.4 K). [2]SbF6 exhibits four phase transitions, and the sum of its transition entropies (ΔStotal = 16.6 J mol–1 K–1) is comparable to that of [1]SbF6. [3]SbF6 exhibits a phase transition from phase I to II, which is a rotator phase (see below), at 271.6 K (ΔS = 33.7 J mol–1 K–1). This transition entropy is quite large and comparable to those of sandwich complexes from an anisotropic crystalline phase to a plastic phase (e.g., [Ru(Cp)(PhMe)]PF6, ΔS = 29.0 J mol–1 K–1 11,14). The transition from phase II to III at 452.3 K (ΔS = 6.8 J mol–1 K–1) is a transition between rotator phases; birefringence was observed in both phases under a polarizing optical microscope, indicating their anisotropic crystal structures (Figure S2).

The phase sequences of the FSA salts are shown in Figure 2b. [1]FSA undergoes a phase transition at 307.4 K (ΔS = 30.6 J mol–1 K–1). [2]FSA and [3]FSA exhibit phase transitions at 358.7 and 350.3 K, followed by melting at 369.2 and 363.3 K, respectively. The details of the melting phenomenon are discussed in the next section.

The phase sequences of salts with other anions (X = CF3BF3 and CB11H12) are shown in Figure 2c. [1]CF3BF3 and [3]CF3BF3 exhibit two and six phase transitions, respectively, which occur at considerably lower temperatures than those of the other salts, probably because the CF3BF3 anion facilitates disorder.16 [1]CF3BF3 undergoes a phase transition from phase I to II at 212.6 K (ΔS = 16.8 J mol–1 K–1), whereas [3]CF3BF3 undergoes three successive phase transitions at approximately 230 K and the sum of the transition entropies (ΔSsum = 15.6 J mol–1 K–1) is comparable to that of [1]CF3BF3. [1]CB11H12, which contains the carborane anion, exhibits three phase transitions above 385.4 K, probably because of the large anion volume, facilitating its molecular rotation only at high temperatures. Other salts such as [2]CF3BF3 could not be synthesized because ligand exchange from [1]CF3BF3 did not occur.34 Similarly, [2]CB11H12 and [3]CB11H12 were not obtained, probably because of anion coordination.39

Most salts showed successive phase transitions as a result of successive order–disorder rearrangements of cations and anions (see below), similar to the salts of sandwich complexes,13 although none of the current salts exhibits an IPC phase; optical birefringence was observed for all phases. This is probably because of the elongated cation shapes compared to that of [M(Cp)2]+, which hinders isotropic rotation. However, the salts exhibit dynamic phases, including rotator phases, as described below.

Melting Behaviors of FSA Salts

We investigated the melting behaviors of [2]FSA and [3]FSA in detail. Interestingly, ligand exchange reactions occurred after melting to form anion-coordinated complexes (Figure 3a).

Figure 3.

Figure 3

Open in a new tab

(a) Ligand exchange reaction of [2]FSA and [3]FSA that occurred upon their melting. (b) POM images of [3]FSA taken during heating. (c) Microscopic image of the crystals grown in the melt of [3]FSA taken under polarized light, after breaking up an aggregate using a needle.

Polarizing optical microscopy (POM) images of the melting behavior of the [3]FSA are shown in Figure 3b. This salt melts at 363 K, after which the deposition of crystals in the melt occurs within 10 min when the liquid is maintained at 383 K, and the crystals dissolve upon further heating to 409 K. [2]FSA exhibits a similar behavior by melting at 369 K, followed by crystal deposition (Figure S3). The entropy change observed by DSC at the melting point was small for this salt (Figure 2) because melting overlapped with the exotherm from the ligand exchange reaction.

X-ray structural analysis of the crystal formed upon melting [3]FSA at 388 K showed the structure to be [3][Rh(cod)(FSA)2]. The compound contains an anionic complex with two FSA anions coordinated to the metal center via N atoms (Figure 3a, right), indicating that the arene ligands of every second cation are exchanged for anions. The molecular structure of this anion is shown in Figure S4. However, we do not provide a detailed structural discussion because of its low data quality (R1[I > 2σ(I)] = 14.4%). Structural analysis of the reaction product of [2]FSA was not possible.

Although several group-11 metal complexes are known to be coordinated via the N atom of FSA or Tf2N (= (CF3SO2)2N–),40−43 very few have been studied such as platinum-group metal complexes.44 A related phenomenon is the formation of the anion-coordinated complex [Ir(cod)(OTf)] (OTf = CF3SO3–) as an intermediate in the ligand exchange reaction of [Ir(cod)(p-xylene)]OTf in solution.45 The formation of anion-coordinated complexes in the liquid phase observedin this study is consistent with this phenomenon.

Thermal Decomposition Behaviors

The thermal stability of [1]X–[3]X (X = SbF6, FSA) was investigated by thermogravimetric (TG) measurements. FSA salts decompose at lower temperatures than SbF6 salts. The TG curves were measured at a scan rate of 3 K min–1 under a nitrogen atmosphere, as shown in Figures 4 and S5. The decomposition temperatures (Tdec = 3 wt % weight loss temperature) determined from the curves are listed in Table 1, together with those of the related salts.

Figure 4.

Figure 4

Open in a new tab

TG traces of (a) SbF6 and (b) FSA salts measured at a scan rate of 3 K min–1 in a nitrogen atmosphere.

Table 1. Decomposition Temperatures (Tdec) of Salts Containing Rh–cod Complexes (K)a.

salt Tdec salt Tdec
[1]SbF6 463 [1]CB11H12c 423
[1′]SbF6 421 [1]CF3BF3b 463
[2]SbF6 511 [1]BArF4b,d 437
[3]SbF6 518 [1]BF4 454
[1]FSA 439 [3]CF3BF3c 453
[2]FSA 407 [3]BF4b,e 447
[3]FSA 423 [4]SbF6 433
    [5]SbF6 441
Open in a new tab
a

Determined by TG measurement (−3 wt %) unless otherwise specified.

b

Determined by visual inspection.

c

Determined by DSC measurement (peak-top temperature).

d

Ref (46).

e

Ref (34) (described as a melting point).

The TG curves of the SbF6 salts are shown in Figure 4a. [1]SbF6 decomposes at 463 K and exhibits a weight loss of approximately 36 wt % up to 548 K owing to the loss of two cod ligands (calculated value: −39 wt %). The decomposition temperature is similar to those of [1]BF4 (454 K, determined by TG, Figure S5c) and [1]BArF4 (Tdec = 437 K, BArF4 = tetrakis((3,5-trifluoromethyl)phenyl)borate),46 indicating that the cation is responsible for the decomposition. The arene-coordinated complexes, [2]SbF6 and [3]SbF6, exhibit considerably higher decomposition temperatures of 511 and 518 K, respectively; [3]SbF6 is more stable owing to the electron-donating substituent in the ligand. Each salt exhibits a weight loss of approximately 65 wt % in one step, which may be ascribed to the loss of cod, arene ligand (calculated value: −37 wt %), and some SbF5 formed by partial decomposition of the anion.

The TG curves of the FSA salts are shown in Figure 4b. The decomposition temperature of [1]FSA is 439 K, approximately 20 K lower than that of [1]SbF6. The weight loss of approximately 34 wt % occurs in one step owing to the loss of two cod ligands (calculated value: −37 wt %). In contrast, the decomposition temperatures of [2]FSA and [3]FSA are 407 and 423 K, respectively, approximately 100 K lower than those of the corresponding SbF6 salts owing to ligand exchange reactions that occur upon melting, as described above. Namely, the decomposition is ascribed to the coordination ability of the anions, which leads to ligand dissociation. These salts exhibit weight losses of 18 and 12 wt %, respectively, within a temperature range of 390–450 K, which corresponds to the loss of arene ligands (calculated values: −16 and −19 wt %, respectively). [1]CB11H12 exhibits a similar decomposition temperature (423 K), which is consistent with the coordination ability of the carborane anion.39

In addition, the decomposition behavior of the Ir complex [1′]SbF6 was investigated. The lower decomposition temperature (Tdec = 421 K) of this salt compared to that of [1]SbF6 (Tdec = 463 K) indicates weaker coordination bonding. A similar tendency has been reported for the melting points of BF4 salts ([1′]BF4:413–418 K, [1]BF4:479–481 K),47 which are probably accompanied by decomposition.

General Features of the Crystal Structures

The crystal structures of phase I of the salts were determined, except for [3]SbF6 and [3]CF3BF3, and the structural changes from phase I to II were crystallographically elucidated for most salts (Figure 5). Their structural features are dependent on the anion, cation, and radius ratio, as summarized in this section. In higher-temperature phases, the structural disorder is enhanced to a larger extent when the transition entropy is large.

Figure 5.

Figure 5

Open in a new tab

Molecular structures (left, ORTEP drawing, 50% probability level) and packing diagrams (right) of [1]X–[3]X. (a,b) SbF6 salts, (c,d) other salts, and (e–g) FSA salts. Less occupied parts of disordered groups are shown in a lighter color.

A correlation was observed between molecular and crystal structures. In phase I, the crystal system of the FSA salts is monoclinic, reflecting low anion symmetry, whereas those of the other salts (X = SbF6, CF3BF3, and CB11H12) are orthorhombic, except for [1]SbF6. The cations and anions are arranged alternately in all the salts, where the number of cations surrounding the anions (coordination number)48 is eight for [1]CB11H12, seven for [2]SbF6, and six for all others in phase I. The cation-to-anion radius ratio ρ, calculated from the van der Waals volumes of the molecules, is 0.87 for CB11H12 salts, whereas it is 0.71, 0.68, and 0.65 for FSA, CF3BF3, and SbF6 salts, respectively. Thus, with the exception of [2]SbF6, the results are consistent with the radius ratio rule for ionic crystals,49 which determines the six-coordinated (0.41 < ρ < 0.73) or eight-coordinated (0.73 < ρ) structures. Interestingly, the coordination number of [1]FSA, whose radius ratio is close to the boundary, changed from six in phase I to eight in phase II, owing to an increase in the effective volume caused by anion disorder in phase II.

Although phase I is an ordered phase for a majority of the salts, structural disorder of this phase increases as the cation symmetry decreases in the order [1]X, [2]X, and [3]X. Both cations and anions are ordered in [1]X (X = SbF6, CF3BF3, and CB11H12) with high packing coefficients (72.8–73.2%), and both exhibit disorder in [2]SbF6, and are even more extensively disordered in [3]X (X = SbF6 and CF3BF3). The FSA salts exhibit less disorder. In each salt, the structural disorder increases, and the crystal symmetry tends to be higher for higher-temperature phases.

Cation disorder is typically a twofold rotational disorder around the long axis, as seen in [2]SbF6 (phases I and II), [1]FSA (phase II), and [1]CF3BF3 (phase II), reflecting the elongated cation shape (Figure 5). Cation structures in other high-temperature phases could not be determined because of extensive disorder. Ordered cations were found in phase I of [1]CF3BF3, [1]CB11H12, and [1]FSA–[3]FSA, with geometries almost identical to those of [Rh(cod)2]X (X = BF4, OTf)50,51 and [Rh(cod)(arene)]SbF6 (arene = hexamethylbenzene, 1,4-dimethylnaphthalene, etc.).5

The structure of each salt is discussed in detail in the following sections.

Crystal Structures of SbF6 Salts

The structural disorder becomes more extensive with a decrease in cation symmetry from 1 to 3. The structure of [1]SbF6 at 90 K (phase I), shown in Figure 5a, has an ordered phase with a coordination number of six. The structure of phase II could not be fully refined because of extensive rotational disorder. The space groups of phases I and II are monoclinic C2/c and orthorhombic A, respectively, with Z = 8 (Table S1), where molecular rotation leads to a higher symmetry in phase II. The corresponding Ir complex [1′]SbF6 is isomorphous, and its unit cell volume is identical to that of [1]SbF6 within the standard deviation (Figure S6). Their molecular structures are almost identical, with M–C(cod) distances of 2.220(2)–2.269(2) Å (M = Rh) and 2.196(7)–2.254(7) Å (M = Ir).

The structures of [2]SbF6 at 90 K (phase I) and 333 K (phase II) are shown in Figure 5b. The structural changes at the phase transition are small; both phases exhibit the Cmcm space group and a coordination number of seven, and their unit cell volumes are almost the same (Z = 4). The cations and anions exhibit rotational disorder in both phases. The cod, benzene ligands, and anion were refined as twofold disordered in phase I (occupancy ratios 0.5:0.5, 0.63(2):0.37(2), and 0.654(5):0.346(5)), whereas the anion required refinement of threefold disorder in phase II, with the occupancies becoming more averaged (occupancy ratios 0.5:0.5, 0.56(3):0.44(3), and 0.402(3):0.302(3):0.296(3)). These small structural changes are consistent with the small phase-transition entropy (ΔS = 2.9 J mol K–1). Phase IV (373 K) has the same unit cell and space group as those in phase II; the structure could not be fully refined owing to extensive disorder (Table S2).

The structure of [3]SbF6 could not be determined because of the extensive rotational disorder of the cations in both phases. The powder X-ray diffraction (PXRD) patterns of [3]SbF6 at 90 K (phase I) and 293 K (phase II) are shown in Figure S7a; the pattern at 293 K is considerably simpler, with fewer peaks than that at 90 K. The crystal systems of these phases are orthorhombic P (Z = 16) and tetragonal I (Z = 2), respectively (Table S7). Molecular rotation (see below) resulted in high crystal symmetry.

Cation Dynamics in SbF6 Salts

The cation motion in [1]SbF6–[3]SbF6 was investigated using solid-state 1H and 2H NMR spectroscopy. As shown in the previous section, X-ray structural analysis revealed that the cation has an ordered structure in [1]SbF6, rotationally disordered structure in [2]SbF6, and extensive disorder in [3]SbF6 at room temperature. To investigate the motion of the cod and arene ligands in the cation independently, salts with benzene-d6 and toluene-d8 ligands (d-[2]SbF6 and d-[3]SbF6, respectively) were synthesized and used for NMR measurements.

The motion of the cod ligand was investigated using 1H NMR spectroscopy. The static 1H NMR spectra of [1]SbF6, d-[2]SbF6, and d-[3]SbF6 recorded at 299 K are shown in Figure 6a, each displaying the proton signal of the cod ligand. The full-width-at-half-maxima of the peaks for [1]SbF6, d-[2]SbF6, and d-[3]SbF6 are 54.0, 19.3, and 8.9 kHz, and the second moments (M2) for the signals are 29.1, 3.7, and 0.8 G2, respectively. The broad signal in [1]SbF6 indicates that the ligand is static, which is consistent with the X-ray structure. The narrow signal in d-[2]SbF6 indicates that the ligand undergoes dynamic reorientation, which demonstrates that the crystallographically observed twofold rotational disorder of cod is dynamic in nature, with the disordered moieties not statically locked in place. A narrow signal was also obtained for d-[3]SbF6 (M2 < 1), indicating that the ligand undergoes extensive motion.52

Figure 6.

Figure 6

Open in a new tab

(a) Solid-state static 1H NMR spectra of [1]SbF6, d-[2]SbF6, and d-[3]SbF6 recorded at 299 K. (b) Solid-state static 2H NMR spectra of (i) d-[2]SbF6 recorded at 299 K and (ii) d-[3]SbF6 recorded at 299 and 263 K. The molecular motions occurring in each phase are illustrated for each spectrum in (b). The frequency of the center of the resonance line of d-[3]SbF6 was set to 0 Hz for the 1H NMR spectra, whereas the center of the Pake doublet of [1]SbF6 was set to 0 Hz for the 2H NMR spectra.

The motions of the deuterated arene ligands in d-[2]SbF6 and d-[3]SbF6 were investigated using 2H NMR spectroscopy. The static 2H NMR spectrum of d-[2]SbF6 measured at 296 K is shown in Figure 6b(i), in which the nuclear quadrupole coupling constant (e2Qq/h) is 88.7 kHz (asymmetry factor η = 0). This value is half that of the static phenyl group (176 kHz),53 indicating that the benzene ligand undergoes continuous rotational diffusion around the molecular long axis. Therefore, although benzene is rotationally disordered according to X-ray analysis, it rotates faster than the NMR time scale. This phase can also be regarded as rotational in a broader sense.

The solid-state static 2H NMR spectra of d-[3]SbF6 in phases II (299 K) and I (263 K) are shown in Figure 6b(ii) and consist of two and three components, respectively. In each spectrum, the innermost Pake doublet represents the methyl-D signal, and its small e2Qq/h value (20.5 kHz in phase II and 20.1 kHz in phase I) indicates continuous rotational motion of the methyl group.54 The outer Pake doublet at 299 K represents the arene-D signal, and its e2qQ/h value (84.3 kHz, η = 0) is approximately 4 kHz smaller than that of [2]SbF6. Line shape analysis revealed that the toluene ligand undergoes continuous rotational diffusion around the molecular long axis, accompanied by precessional motion (γ = 10.4°) of the cation along the molecular long axis, as illustrated in the figure. In contrast, two types of Pake doublets are observed for arene-D at 263 K, indicating the presence of nearly static and dynamic cations. The e2qQ/h value of the outer signal (165.7 kHz) is approximately 10 kHz smaller than that of the static phenyl group, indicating that the ring rotation is nearly frozen, although a slight precessional motion of the cation still exists (γ = 11.4°). The small e2qQ/h value of the inner signal (48.1 kHz) indicates extensive cation motion, which is analyzed as the continuous rotation of the phenyl ring and large precessional motion of the cation (γ = 33.3°). Alternatively, a larger precessional motion (γ = 44.1°) without molecular rotation would produce the same line shape; however, this seems less plausible.

These analyses reveal the characteristic molecular motion of the Rh–cod cations. The 1H and 2H NMR spectra consistently account for the X-ray structure, and the results suggest the dynamic nature of the twofold disorder of cod observed in other salts. In addition, [3]SbF6 has been demonstrated to exhibit a rotator phase in which the molecules undergo extensive but anisotropic rotation. Considering these results, the room-temperature phase of [3]CF3BF3 and the high-temperature phases of the other salts are probably rotator phases with extensive molecular motion, similar to [3]SbF6. However, this could not be confirmed experimentally because of the high temperatures or narrow temperature range.

Crystal Structures of CF3BF3 and CB11H12 Salts

The crystals of [1]CF3BF3, [1]CB11H12, and [3]CF3BF3 belong to an orthorhombic crystal system in phase I, similar to most SbF6 salts. [3]CF3BF3 exhibits extensive structural disorder.

The structures of [1]CF3BF3 determined at 90 K (phase I) and 223 K (phase II) are shown in Figure 5c. Phase I is an ordered phase with space group Aba2 (Z = 16). The two pairs of cations and anions are crystallographically independent, and the coordination number is six. The crystal symmetry in phase II is higher (space group Pnnm, Z = 2). Phase II is regarded as the averaged structure of phase I, having only one cation–anion pair in the asymmetric unit, with the cation best refined as twofold rotationally disordered (occupancy ratio 0.642(15):0.358(15)). The anion occupies a special position of the twofold rotational axis and mirror plane, with an occupancy ratio of 0.25. As a result, the carbon and boron atoms are refined as twofold rotationally disordered (occupancy ratio 0.5:0.5), occupying almost the same position, and the fluorine atoms are refined as fourfold disordered by rotation (occupancy ratio 0.25). The molecular arrangements in phases I and II are almost identical, with slight shifts in their molecular positions (Figure S8). This structure differs from that of [1]OTf (space group C2/c at room temperature, ordered structure),50 despite the presence of structurally similar anions.

The structure of [1]CB11H12 at 90 K (phase I) in Figure 5d clearly shows an ordered phase. This phase crystallizes in the space group Pnma (Z = 4), exhibiting a coordination number of eight owing to the large size of the anion. The anion geometry is almost identical to those of other reported salts.55

The structures of [3]CF3BF3 in both phases are extensively disordered and not satisfactorily refined, similar to those of [3]SbF6. The apparent crystal systems of phases I (90 K) and IV (248 K), based on the unit cell dimensions, are orthorhombic and tetragonal, respectively (Z = 2). The PXRD patterns of this salt, shown in Figure S7b, are similar to those of [3]SbF6 (Figure S7a). In particular, the patterns of the high-temperature phases are almost identical to each other, indicating that their structures are isomorphic, which is reasonable considering their similar anion volumes.

Crystal Structure of FSA Salts

The FSA salts [1]FSA–[3]FSA have a lower crystal symmetry than the other salts, reflecting their low anion symmetry.

The structures of [1]FSA at 90 K (phase I) and 333 K (phase II) are shown in Figure 5e. Phase I crystallizes in space group P21/c (Z = 4) and exhibits an ordered structure, whereas phase II crystallizes in space group C2/c (Z = 4) and exhibits extensive disorder. The molecular long axes of the cations are canted with each other in phase I, but they are nearly parallel in phase II (Figure 5e). The cation in phase II is refined as twofold disordered by rotation (occupancy ratio 0.516(15):0.484(15)), and the anion is also refined as disordered with two equally occupied symmetry equivalent moieties. Such order–disorder in the FSA anion upon phase transition is often observed.56−59 The coordination number change from six in phase I to eight in phase II is ascribed to an effective change in the radius ratio caused by the disorder of the anion. These large structural changes are consistent with the large transition entropy (30.6 J mol K–1).

The crystal structures of [2]FSA and [3]FSA at 90 K (phase I) are shown in Figure 5f–g. They crystallize in the space groups P21/c and P21/n, respectively (Z = 4). The cations in both structures are ordered, but the anion in [2]FSA exhibits twofold disorder (occupancy ratio 0.581(5):0.419(5)). The proximity of their melting points prevented the collection of diffraction data for phase II in these salts.

Ligand Exchange Reactions

To explore the solid-state reactivity of Rh–cod complexes, we investigated the ligand exchange reactions of SbF6 salts using single crystals and found that [3]SbF6 and [2]SbF6 undergo an in situ SC–SC reaction.

Single crystals of [3]SbF6 (0.5 mg, typical size: ∼150 × 50 × 50 μm3) were immersed in diethyl ether (5 mL), followed by the addition of a very small amount of the coordinating solvent (SMe2 or CH3CN, 4 μL). The sample was left to stand for 3 days, during which the ligand exchange reaction proceeded gradually in an SC–SC manner (Figure 7a,b and Table 2). [3]SbF6 and its products were yellow crystals insoluble in the solvent, and the structures of the SC–SC reaction products [4]SbF6 and [5]SbF6 were confirmed by single-crystal X-ray structural analysis (see below). The reaction occurred on the surface, which was visually observable under a polarizing optical microscope, as thick crystals did not allow the reaction to proceed into the interior. This resulted in overall conversions of 52 and 14%, respectively, over 3 days, as confirmed by 1H NMR spectra.

Figure 7.

Figure 7

Open in a new tab

(a) In situ ligand exchange reaction of single crystals of [3]SbF6 performed in a diethyl ether medium. (b) Conversion from [3]SbF6 to [4]SbF6 or [5]SbF6, captured for the same samples during ligand exchange reactions in ether. (c) Oxidation reaction of [4]+. The X-ray structure of the cation is shown on the right.

Table 2. Morphology of Products Formed by In Situ Reactions of [1]SbF6–[3]SbF6 with Coordinating Molecules (L′) Using Single Crystals [SC = Single Crystal, A = Amorphous]a.

  reaction in diethyl ether
 reaction with vapor (5 min)
L′ [1]SbF6 [2]SbF6 [3]SbF6 [1]SbF6 [3]SbF6
SMe2 A (76%, 1 day) SC (92%, 3 days) SC (52%, 3 days) A (99%) A (98%)
MeCN A (100%, 1 h) SC (17%, 3 days) SC (14%, 3 days) oilb oilb
Open in a new tab
a

Conversion and reaction time are shown in parenthesis.

b

Oil is gradually formed during reaction.

Single crystals of [2]SbF6 (∼50 × 50 × 20 μm3) also exhibited SC–SC ligand exchange reactions for SMe2 and CH3CN under similar conditions, with overall conversions of 92 and 17%, respectively (Table 2). The higher conversion compared to that of [3]SbF6 is ascribed to its smaller crystal size.

Interestingly, the addition of a large excess of SMe2 to dissolve [3]SbF6 in air resulted in the deposition of a mixture of [4]SbF6 and of the new salt [Rh(C8H12O)(SMe2)3]SbF6 ([6]SbF6) over the range of 2 weeks. The cation of the latter consists of a ligand and central metal in the oxidized state. The structure determined by crystallographic analysis is shown in Figure 7c. The formation of similar compounds by the oxidation of cod complexes is known;60,61 hence, the reaction observed here probably also occurred by the air oxidation of the cation in solution.

In contrast, the reaction of [1]SbF6 proceeded in a considerably shorter time without maintaining crystallinity. The reaction of [1]SbF6 with SMe2 and CH3CN in diethyl ether proceeded in 76% (in a day) and 100% (in 1 h) yields, respectively, both changing from red-brown crystals to lumpy yellow amorphous solids (Table 2, Figure S9). The reaction with SMe2 was slower than that with CH3CN. The faster reaction of [1]SbF6 than those of [2]SbF6 and [3]SbF6 is probably ascribed to the easier dissociation of the cod ligand than that of the arene ligands,34 which is also consistent with their thermal decomposition behavior (Figure 4a).

For comparison, the direct reactions of single crystals of [1]SbF6 and [3]SbF6 with solvent vapors were examined. The reactions proceeded quantitatively in a considerably shorter time without maintaining crystallinity (Figure S10). Exposure to SMe2 vapor for 5 min produced amorphous products, even for [3]SbF6, indicating that a very fast reaction results in crystallinity loss. Exposure to CH3CN vapor resulted in the formation of yellow liquids, which is ascribed to the presence of released ligands in the products. Therefore, the use of ether as a medium is advantageous to slow down the reaction speed because of dilution, and the released ligand is efficiently removed, preventing the formation of an oily mixture.

[2]SbF6 and [3]SbF6 are both dynamically disordered crystals, and this feature may facilitate the SC-SC reactions. However, because both salts undergo the SC–SC reaction in a similar manner, the correlation between reactivity and rotational phase is not clear from the current experiments. Although many examples of SC–SC reactions in coordination compounds have already been reported,62 the current reaction is important because it involves Rh–cod precatalysts and can be potentially extended to solid-state catalytic reactions. In the current SC–SC reactions, ether may have a role in assisting molecular diffusion at the surface, similar to solvent-assisted solid-state reactions.63 These points require further investigation.

Characterization of the Ligand-Exchanged Products

The crystal structures of the single crystals of [4]SbF6 and [5]SbF6 obtained via in situ SC–SC ligand exchange were determined along with their thermal properties.

The structure of the as-formed crystal of [4]SbF6 determined at 90 K (phase I) is shown in Figure 8a. This salt crystallizes in the triclinic space group P-1 (Z = 2) with a coordination number of six. One cation and two half anions are crystallographically independent, and the Rh–S bond distances are 2.370(1) and 2.3824(9) Å, respectively. The crystal structures of [5]SbF6 were determined at 90 K (phase I) and 293 K (phase II) because of the phase transition at 136 K (see below). We also confirmed that the crystal structure of [5]SbF6 synthesized by the SC–SC reaction is identical to that obtained by recrystallization of an authentic sample from dichloromethane-diethyl ether (Table S3). Phase I crystallizes in space group C2/c (Z = 8). Two half pairs of cations and anions are present in the asymmetric unit of the structure and are crystallographically independent, and all four ions are located on the crystallographic twofold axes. Phase II crystallizes in space group Fddd (Z = 16). The crystal symmetry is higher, and the unit cell volume is twice that of phase I, but the molecular arrangements are almost identical (Figures 8b and S11). One half cation, located on a twofold axis, and two quarters of the occupied anions, located at the intersections of two twofold axes, are crystallographically independent. Anion I is surrounded by acetonitrile molecules and is ordered, whereas anion II is surrounded by cod and is refined as twofold disordered by rotation (occupancy ratio 0.876(8):0.124(8)), probably because of the larger space surrounding the anion. The small transition entropy from phase I to II (4.4 J mol K–1) is consistent with this rather small structural change. The cation has Rh–N bond lengths of 2.07–2.08 Å and exhibits virtually identical structure as that in [5]BF4.6

Figure 8.

Figure 8

Open in a new tab

Packing diagrams of (a) [4]SbF6 and (b) [5]SbF6. ORTEP drawing of the cation is shown in (a). Crystallographically independent molecules are labeled as I and II.

DSC measurements revealed no phase transitions for [4]SbF6 and decomposition at 433 K without melting, whereas [5]SbF6 exhibited a solid phase transition at 136.0 K (ΔS = 4.4 J mol–1 K–1), followed by melting at 410.6 K (ΔSm = 61.7 J mol–1 K–1, Figure S1a). Its melting point is approximately 50 K lower than that of [5]BF4 (Tm = 461–463 K64). Upon cooling from the melt, the salt exhibited glass transition at 279.8 K, and cold crystallization and melting occurred during its reheating.

The TG charts for these salts are shown in Figure 9. The decomposition temperature (3 wt %) of [4]SbF6 is 433 K, and a slight weight loss starts at approximately 350 K. The loss of the two SMe2 molecules occurs in two steps, exhibiting a weight loss of approximately 10 wt % in each step, up to 460 and 520 K (calculated value for the loss of one SMe2: 11 wt %), and a weight loss of approximately 34 wt % is observed between 520 and 600 K, which corresponds to the losses of cod and some SbF5 formed by partial decomposition of the anion. The decomposition temperature (−3 wt %) of [5]SbF6 is 441 K, exhibiting a one-step weight loss of 36 wt % up to 518 K. This corresponds to the loss of two acetonitrile molecules and cod (calculated value: 36 wt %). These salts are less thermally stable than [1]SbF6 and exhibit ligand desorption at lower temperatures. In particular, the slight weight loss initiated at relatively low temperatures in [4]SbF6 is consistent with its tendency to gradually decompose in air. Furthermore, the slower reaction of [1]SbF6 with SMe2 than with CH3CN in diethyl ether (Table 2) is consistent with the lower thermal stability of [4]SbF6 than that of [5]SbF6.

Figure 9.

Figure 9

Open in a new tab

TG curves of [1]SbF6, [4]SbF6, and [5]SbF6, measured at a scan rate of 3 K min–1 in a nitrogen atmosphere.

The syntheses of structurally related salts, [5]ClO4,65 [Rh(cod)(dmso)2]BF4,66 and [Rh(cod)(H2O)2]OTf,67 have been reported, of which [Rh(cod)(dmso)2]BF4 and [Rh(cod)(H2O)2]OTf have been structurally characterized. [Rh(cod)(H2O)2]OTf exhibits a phase transition at 215 K,67 where the order–disorder of the anion occurs, similar to [4]SbF6.

Conclusions

In this study, the thermal properties and crystal structures of cationic Rh–cod complexes with cyclic ligands were investigated. These salts exhibit solid phase transitions, through which the disorder and crystal symmetry increase in higher-temperature phases. Crystal symmetry typically depends on the anion, whereas less symmetrical cations tend to exhibit more severely disordered phases. [Rh(cod)(PhMe)]SbF6 exhibits a rotator phase at room temperature, whereas the other salts exhibit dynamically disordered phases. In contrast to the salts of sandwich complexes, no structurally isotropic IPC phase was found owing to the elongated, ellipsoidal shape of the cations. We also investigated the thermal stabilities and chemical reactivities of these salts. FSA salts with arene ligands undergo ligand exchange reactions upon melting, leading to lower thermal stability. Salts with arene ligands undergo in situ ligand exchange in ether via an SC–SC reaction. The insights obtained in this study provide fundamental information that is useful for the development and application of organometallic reactions because the catalytic reactivities of Rh–cod complexes are based on their coordination abilities. Furthermore, this knowledge will be useful for the future exploration of organometallic solid-state reaction chemistry, including catalytic reactions.

Experimental Section

General

All reactions were performed under a nitrogen atmosphere, and dehydrated solvents were used. [M(cod)2]SbF6 (M = Rh, Ir),35 [Rh(cod)2]BF4,68 AgFSA,40 and AgCB11H1269 were synthesized according to previously reported procedures. AgCF3BF3·nCH3CN was obtained as a hygroscopic white powder by the reaction of KCF3BF3 and silver nitrate in acetonitrile. The white precipitate of potassium nitrate formed during the reaction was removed by filtration, and the filtrate was concentrated, followed by the addition of diethyl ether. The desired compound precipitated after standing the solution at 233 K for a day, which was collected by filtration. Other reagents were purchased from TCI. 1H NMR spectra were recorded on a Bruker Advance 400 spectrometer. FTIR spectra were acquired using a Thermo Nicolet iS5 spectrometer fitted with attenuated total reflectance (ATR). DSC measurements were performed using a TA Q100 differential scanning calorimeter at a scan rate of 10 K min–1 using aluminum hermetic pans as sample containers. TG-DTA measurements were performed using a Rigaku TG8120 thermal analyzer at a scan rate of 3 K min–1 under a nitrogen atmosphere. Solid-state NMR spectra were recorded on a Tecmag Apollo spectrometer (operating at 46.045 MHz for 2H and 299.95 2 MHz for 1H) equipped with a Doty XC MAS 4 mm probe head. The 1H NMR spectra were measured with a 3.9 μs π/2 pulse. The 2H spectra were measured with a solid echo pulse sequence [π/2 – τ – π/2 – τ – acquisition],70 using a 4.6 μs π/2 pulse and a delay time τ of 40 μs. The recycle delays for the 1H and 2H measurements were 7 s and 3 s, respectively.

Synthesis of Metal Complexes

[Rh(cod)2]X ([1]X; X = FSA, CB11H12, CF3BF3)

These salts were synthesized using a method similar to that of [Rh(cod)2]SbF6.35 The synthesis of [Rh(cod)2]FSA is described below as an example. 1,5-Cyclooctadiene (29 mg, 0.31 mmol) was added to a solution of [Rh(cod)Cl]2 (50 mg, 0.10 mmol) in dichloromethane (2 mL) under stirring. An acetone solution (1 mL) of AgFSA (79 mg, 0.23 mmol) was added, and a white precipitate was immediately formed. The suspension was stirred for 1 h, and the white solid was removed by Celite filtration. The filtrate was concentrated using a rotary evaporator, to which hexane (5 mL) was added. A reddish-brown oil phase containing the desired product was separated, the hexane phase was removed with a pipette, and the remaining oil was washed with hexane (5 mL × 2) and diethyl ether (5 mL × 3). The remaining solvent was removed under reduced pressure, and recrystallization of the resultant solid from dichloromethane-diethyl ether at 233 K resulted in the desired product as reddish brown crystals (78 mg, 78% yield). 1H NMR (400 MHz, CDCl3): δ = 2.47–2.68 (m, 16H, CH2), 5.34 (br, 8H, CH). FTIR (ATR, cm–1): 564, 736, 823, 1105, 1171, 1360, 1427, 2891. Anal. calcd. for C16H24F2NO4RhS2: C, 38.48; H, 4.84; N, 2.80. Found: C, 38.42; H, 5.02; N, 2.87. The other salts were synthesized in a similar manner using the corresponding silver salts. [Rh(cod)2]CB11H12: reddish brown crystals (20% yield). 1H NMR (400 MHz, CDCl3): δ = 0.81–0.91 (br, 11H, BH), 2.18 (s, 1H, CHBH11) 2.35–2.54 (m, 16H, CH2), 5.11 (br, 1H, cod–CH), 5.29 (br, 2H, cod–CH), 5.59 (br, 5H, cod–CH). FTIR (ATR, cm–1): 716, 783, 860, 1001, 1023, 1065, 1426, 1472, 2509. Anal. calcd. for C17H36B11Rh: C, 44.17; H, 7.85; N, 0.00. Found: C, 43.55; H, 7.40; N, 0.12. [Rh(cod)2]CF3BF3: reddish brown crystals (29% yield). 1H NMR (400 MHz, CDCl3): δ = 2.46–2.69 (m, 8H, CH2), 5.33 (br, 4H, CH). FTIR (ATR, cm–1): 632, 783, 829, 862, 946, 970, 1043, 1430. Anal. calcd. for C17H24BF6Rh: C, 44.77; H, 5.30; N, 0.00. Found: C, 44.67; H, 5.36; N, 0.07.

[Rh(cod)L]X ([2]X: L = C6H6, [3]X: L = PhMe, X = SbF6, FSA)

The synthesis of [Rh(cod)(PhMe)]SbF6 is described below as an example. Toluene (325 mg, 3.5 mmol) was added to a solution of [Rh(cod)Cl]2 (349 mg, 0.81 mmol) in dichloromethane (5 mL) with stirring. In sequence, a solution of AgSbF6 (510 mg, 1.7 mmol) in acetone (1 mL) was added to this solution to form a white precipitate. The suspension was stirred for 1 h, and the solid was removed by Celite filtration. The filtrate was concentrated using a rotary evaporator, followed by addition of hexane (5 mL). A yellow oil phase containing the desired product was separated, the hexane phase was removed using a pipette, and the remaining oil was washed with hexane (5 mL × 2) and diethyl ether (5 mL × 3). The remaining solvent was removed under reduced pressure, and recrystallization of the resultant solid from dichloromethane-diethyl ether (233 K) resulted in the desired product as yellow crystals (618 mg, yield 81%). 1H NMR (400 MHz, CDCl3): δ = 2.08–2.17 (m, 8H, CH2), 2.35–2.45 (m, 8H, CH2), 2.39 (s, 3H, CH3), 4.65 (br, 4H, CH), 6.68–6.74 (m, 3H, arene–H), 6.77–6.82 (m, 2H, arene–H). FTIR (ATR, cm–1): 647, 807, 889, 990, 1165, 1452, 1549. Anal. calcd. for C15H20F6RhSb: C, 33.43; H, 3.74; N, 0.00. Found: C, 33.37; H, 3.77; N, 0.08. The corresponding deuterated complex [Rh(cod)(C6D5CD3)]SbF6 (d-[3]SbF6) was synthesized using toluene-d8 (84% yield). The other salts were synthesized in a similar manner using the corresponding ligands and silver salts. [Rh(cod)(C6H6)]SbF6: Yellow crystals (19% yield). 1H NMR (400 MHz, CDCl3): δ = 2.11–2.19 (m, 4H, CH2), 2.36–2.46 (m, 4H, CH2), 4.83 (br, 4H, CH), 6.87 (s, 6H, C6H6). FTIR (ATR, cm–1): 647, 785, 827, 891, 990, 1010, 1163, 1309, 1337, 1443, 1464. Anal. calcd. for C14H18F6RhSb: C, 32.03; H, 3.46; N, 0.00. Found: C, 31.81; H, 3.38; N, 0.08. The corresponding deuterated complex [Rh(cod)(C6D6)]SbF6 (d-[1]SbF6) was synthesized using benzene-d6 and acetone as the solvents. In this case, benzene-d6 was added to the recrystallization solvent to suppress ligand dissociation (60% yield). [Rh(cod)(PhMe)]FSA: Yellow crystals (45% yield). 1H NMR (400 MHz, CDCl3): δ = 2.11–2.20 (m, 4H, CH2), 2.35–2.45 (m, 4H, CH2), 2.42 (s, 3H, CH3), 4.67 (br, 4H, CH), 6.72–6.78 (m, 3H, arene–H), 6.81–6.87 (m, 2H, arene–H). FTIR (ATR, cm–1): 564, 727, 826, 1101, 1174, 1216, 1360, 1451, 2842. Anal. calcd. for C15H20F2NO4RhS2: C, 37.27; H, 4.17; N, 2.90. Found: C, 37.27; H, 4.19; N, 2.83. [Rh(cod)(C6H6)]FSA: Yellow crystals (19% yield). 1H NMR (400 MHz, CDCl3): δ = 2.11–2.19 (m, 4H, CH2), 2.36–2.46 (m, 4H, CH2), 4.83 (br, 4H, CH), 6.87 (s, 6H, C6H6). FTIR (ATR, cm–1): 563, 737, 824, 1098, 1171, 1360, 1549, 1622, 2955. Anal. calcd. for C14H18F2NO4RhS2: C, 35.83; H, 3.87; N, 2.98. Found: C, 35.34; H, 3.76; N, 2.91.

[Rh(cod)(PhMe)]CF3BF3 ([3]CF3BF3)

The salt was prepared using a similar method to that of [Rh(cod)(PhMe)]BF4.34 Toluene (1 mL) was added to a solution of [Rh(cod)2]CF3BF3 (26 mg, 0.05 mmol) in dichloromethane (2 mL) under stirring, and the mixture was further stirred for 3 days. The solution was concentrated using a rotary evaporator, followed by addition of diethyl ether (10 mL). Subsequently, a pale orange solid precipitated and was collected by filtration. Recrystallization from dichloromethane/diethyl ether (233 K) yielded orange crystals (21 mg, 84% yield). 1H NMR (400 MHz, CDCl3): δ = 2.08–2.17 (m, 4H, CH2), 2.34–2.44 (m, 4H, CH2), 2.39 (s, 3H, CH3), 4.65 (br, 4H, CH), 6.70–6.77 (m, 3H, arene–H), 6.79–6.84 (m, 2H, arene–H). FTIR (ATR, cm–1): 631, 782, 828, 863, 947, 970, 1043, 1429, 1449. Anal. calcd. for C12H18F6N2RhSb: C, 43.67; H, 4.58; N, 0.00. Found: C, 43.48; H, 4.74; N, 0.00.

[Rh(cod)(CH3CN)2]SbF6 ([5]SbF6)

Diethyl ether (5 mL) was added to a solution of [Rh(cod)2]SbF6 (30 mg, 0.05 mmol) in acetonitrile (1 mL). A yellow solid was precipitated, which was collected by filtration, and recrystallization of the solid from dichloromethane-diethyl ether at 233 K yielded yellow crystals. The second crop was also collected and combined (76% yield). 1H NMR (400 MHz, CDCl3): δ = 1.86–1.96 (m, 4H, CH2), 2.35 (s, 6H, CH3), 2.44–2.54 (m, 4H, CH2), 4.40 (br, 4H, CH). FTIR (ATR, cm–1): 652, 877, 981, 1005, 1027, 1082, 1166, 1228, 1314, 1337, 1409, 1437, 2284, 2311. Anal. calcd. for C12H18F6N2RhSb: C, 27.75; H, 3.43; N, 5.30. Found: C, 27.40; H, 3.31; N, 5.16.

Ligand Exchange Reactions

Ligand exchange reactions using single crystals of [2]SbF6 and [3]SbF6 were performed in diethyl ether. The crystals (0.5 mg) were placed in diethyl ether (5 mL) under a nitrogen atmosphere. These salts were insoluble in ether. A small amount of SMe2 or acetonitrile (4 μL) was added to the solvent, which was left unperturbed, and the solids were gradually converted to [Rh(cod)(SMe2)2]SbF6 ([4]SbF6) and [5]SbF6 without any change in appearance. The conversions of [2]SbF6 to [4]SbF6 and [5]SbF6 were 92 and 17%, respectively, whereas those of [3]SbF6 were 52 and 14%, respectively, as determined using 1H NMR spectroscopy (CDCl3). The reactions of [1]SbF6 with SMe2 or acetonitrile were performed in a similar manner. In this case, the appearance changed from reddish-brown block crystals to yellow solids, and the conversions were 76% (1 day) and 100% (after 1 h) for the reactions with SMe2 and acetonitrile, respectively. The crystals of [4]SbF6 gradually decomposed in air and turned green over a few days. To avoid possible degradation, the samples recrystallized from dichloromethane-diethyl ether (233 K) were immediately used for the TG-DTA and DSC measurements. [4]SbF6: 1H NMR (400 MHz, CDCl3): δ = 2.06–2.18 (m, 4H, CH2), 2.31 (s, 12H, CH3), 2.50–2.63 (m, 4H, CH2), 4.55 (br, 4H, CH). FTIR (ATR, cm–1): 649, 857, 980, 1031, 1306, 1335, 1430. Anal. calcd. for C12H18F6N2RhSb: C, 25.24; H, 4.24; N, 0. Found: C, 24.84; H, 3.65; N, 1.17. The discrepancy in the analytical data was ascribed to slight decomposition. Upon addition of a large excess of SMe2 (0.5 mL) to [3]SbF6 (0.5 mg) in diethyl ether, part of the crystal dissolved, and upon standing the solution, a solid mixture of [4]SbF6 and an oxidation product [Rh(C8H12O)(SMe2)3]SbF6 ([6]SbF6) (molar ratio ∼ 0.8:0.2) were deposited over 2 weeks. The structure of the latter was determined using X-ray crystallography. [6]SbF6:1H NMR (400 MHz, CDCl3): δ = 2.08 (m, 4H, RhCHCH2-endo, OCHCH2-endo), 2.59 (m, 4H, RhCHCH2-exo, OCHCH2-exo), 2.63 (s, 9H, CH3), 3.04 (m, 2H, RhCH), 5.87 (m, 2H, OCH).

The reactions with solvent vapors were performed as follows: A small vial (1 mL) containing [1]SbF6 or [3]SbF6 crystals (0.5 mg) was placed in a larger vial (10 mL) under a nitrogen atmosphere. A small amount of the solvent (CH3CN or SMe2; 0.1 mL) was placed in an outer vial, sealed, and allowed to stand at room temperature for 5 min. [1]SbF6 and [3]SbF6 reacted with SMe2 vapor to form [4]SbF6 as a yellow amorphous solid in almost quantitative yield. The conversion was confirmed using 1H NMR spectroscopy (CDCl3). The reactions with CH3CN vapor proceeded quantitatively to result in a yellow liquid, which yielded solid [5]SbF6 after vacuum-drying.

X-Ray Crystallography

X-ray diffraction data were collected using a Bruker APEX II Ultra diffractometer (X-ray source: MoKα rotating anode), and calculations were performed using SHELXL71 (software: APEX372). Packing diagrams were drawn using Mercury software,73 and the packing indices were calculated using Platon.74 [1]CF3BF3 (phase II) and [5]SbF6 (phase I) were twinned; therefore, TWINABS75 was used for scaling and empirical absorption correction, and the second component contribution was modeled using the HKLF5 refinement. PXRD patterns were calculated using XPREP76 from the single-crystal hkl reflection data. The unit cell parameters were based on single-crystal unit cell determination. The crystallographic parameters are listed in Tables S1–S7. For the structural determination of [3][Rh(cod)(FSA)2], single crystals formed from a molten liquid of [3]FSA were used, and the data were collected at 388 K to prevent solidification of unreacted [3]FSA. The data quality was less satisfactory because of the high data collection temperature and gradual crystal degradation. Other crystals were obtained by recrystallization from organic solvents. CSD numbers: CCDC-2183669–2183683 and 2193891 contain the crystallographic data for [1]SbF6, [1′]SbF6, [2]SbF6, [2]SbF6 (phase II), [1]FSA, [1]FSA (phase II), [2]FSA, [3]FSA, [1]CF3BF3, [1]CF3BF3 (phase II), [1]CB11H12, [5]SbF6, [5]SbF6 (phase II), [4]SbF6, [3][Rh(cod)(FSA)2], and [6]SbF6.

Acknowledgments

This work was financially supported by KAKENHI (grant number: 20H02756) from the Japan Society for the Promotion of Science (JSPS) and a Grant-in-Aid for JSPS Research Fellows (grant number: 21J12056). We are grateful to the anonymous reviewers for their valuable comments.

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.inorgchem.2c03865.

  • DSC charts, POM images, crystal structures, TG-DTA charts, PXRD patterns, infrared spectra, and crystallographic parameters (PDF)

The authors declare no competing financial interest.

Supplementary Material

ic2c03865_si_001.pdf (944.7KB, pdf)

References

  1. Ojima I.; Vu A. T.; Bonafoux D.Product Class 5: Organometallic Complexes of Rhodium. In Science of Synthesis; Lautens M., Ed.; Thieme Verlag, 2001; pp 531–616. [Google Scholar]
  2. Garralda M. A.; Oro L. A. Cationic Rhodium(I) Diolefin Complexes. Transition Met. Chem. 1980, 5, 65–73. 10.1007/BF01396872. [DOI] [Google Scholar]
  3. Osborn J. A.; Schrock R. R. Coordinatively Unsaturated Cationic Complexes of Rhodium(I), Iridium(I), Palladium(II), and Platinum(II). Generation, Synthetic Utility, and Some Catalytic Studies. J. Am. Chem. Soc. 1971, 93, 3089–3091. 10.1021/ja00741a069. [DOI] [Google Scholar]
  4. Emerson-King J.; Knighton R. C.; Gyton M. R.; Chaplin A. B. Rotaxane Synthesis Exploiting the M(I)/M(III) Redox Couple. Dalton Trans. 2017, 46, 11645–11655. 10.1039/C7DT02648J. [DOI] [PubMed] [Google Scholar]
  5. Wender P. A.; Williams T. J. [(arene)Rh(cod)]+ Complexes as Catalysts for [5+2] Cycloaddition Reactions. Angew. Chem., Int. Ed. 2002, 41, 4550–4553. . [DOI] [PubMed] [Google Scholar]
  6. Kang S. O.; Lynch V. M.; Day V. W.; Anslyn E. V. Enthalpy- vs Entropy-Driven Complexation of Homoallylic Alcohols by Rhodium(I) Complexes. Organometallics 2011, 30, 6233–6240. 10.1021/om200793p. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Toda F., Ed.; Organic Solid State Reactions; Springer: Berlin Heidelberg, 2005. [Google Scholar]
  8. Sheng M.; Yang Q.; Huff D.; Schafer A. G.; Tucker C.; Valco D. Thermal Instability and Associated Potential Safety Hazards of Rhodium(I) Precatalyst Complexes with Weakly Coordinated Ligands. Org. Process Res. Dev. 2021, 25, 1054–1064. 10.1021/acs.oprd.1c00061. [DOI] [Google Scholar]
  9. Togni A.; Hayashi T., Eds.; Ferrocenes: Homogeneous Catalysis, Organic Synthesis, Materials Science; Wiley-VCH Verlag: Weinheim, Germany, 1995. [Google Scholar]
  10. Stepnicka P., Ed.; Ferrocenes: Ligands, Materials and Biomolecules; Wiley-Blackwell: Hoboken, NJ, 2008. [Google Scholar]
  11. Webb R. J.; Lowery M. D.; Shiomi Y.; Sorai M.; Wittebort R. J.; Hendrickson D. N. Ferrocenium Hexafluorophosphate: Molecular Dynamics in the Solid State. Inorg. Chem. 1992, 31, 5211–5219. 10.1021/ic00051a011. [DOI] [Google Scholar]
  12. Grepioni F.; Cojazzi G.; Draper S. M.; Scully N.; Braga D. Crystal Forms of Hexafluorophosphate Organometallic Salts and the Importance of Charge-Assisted C–H---F Hydrogen Bonds. Organometallics 1998, 17, 296–307. 10.1021/om9706626. [DOI] [Google Scholar]
  13. Mochida T.; Funasako Y.; Ishida M.; Saruta S.; Kosone T.; Kitazawa T. Crystal Structures and Phase Sequences of Metallocenium Salts with Fluorinated Anions: Effects of Molecular Size and Symmetry on Phase Transitions to Ionic Plastic Crystals. Chem. −Eur. J. 2016, 22, 15725–15732. 10.1002/chem.201603170. [DOI] [PubMed] [Google Scholar]
  14. Tominaga T.; Ueda T.; Mochida T. Effect of Substituents and Anions on the Phase Behavior of Ru(II) Sandwich Complexes: Exploring the Boundaries between Ionic Liquids and Ionic Plastic Crystals. Phys. Chem. Chem. Phys. 2017, 19, 4352–4359. 10.1039/C6CP08308K. [DOI] [PubMed] [Google Scholar]
  15. Mochida T.; Ishida M.; Tominaga T.; Takahashi K.; Sakurai T.; Ohta H. Paramagnetic Ionic Plastic Crystals Containing the Octamethylferrocenium Cation: Counteranion Dependence of Phase Transitions and Crystal Structures. Phys. Chem. Chem. Phys. 2018, 20, 3019–3028. 10.1039/C7CP02746J. [DOI] [PubMed] [Google Scholar]
  16. Kimata H.; Mochida T. Effects of Molecular Structure on Phase Transitions of Ionic Plastic Crystals Containing Cationic Sandwich Complexes. Cryst. Growth Des. 2018, 18, 7562–7569. 10.1021/acs.cgd.8b01390. [DOI] [Google Scholar]
  17. Pringle J. M. Recent Progress in the Development and Use of Organic Ionic Plastic Crystal Electrolytes. Phys. Chem. Chem. Phys. 2013, 15, 1339–1351. 10.1039/C2CP43267F. [DOI] [PubMed] [Google Scholar]
  18. Ishida H.; Iwachido T.; Hayama N.; Ikeda R.; Terashima M.; Nakamura D. Self-Diffusion and Reorientation of Methylammonium Ions in (CH3NH3)2ZnCl4 Crystals as Studied by 1H-NMR. Z. Naturforsch., A 1989, 44, 741–746. 10.1515/zna-1989-0811. [DOI] [Google Scholar]
  19. Matsumoto K.; Harinaga U.; Tanaka R.; Koyama A.; Hagiwara R.; Tsunashima K. The Structural Classification of the Highly Disordered Crystal Phases of [Nn][BF4], [Nn][PF6], [Pn][BF4], and [Pn][PF6] Salts (Nn+ = Tetraalkylammonium and Pn+ = Tetraalkylphosphonium). Phys. Chem. Chem. Phys. 2014, 16, 23616–23626. 10.1039/C4CP03391D. [DOI] [PubMed] [Google Scholar]
  20. Enomoto T.; Kanematsu S.; Tsunashima K.; Matsumoto K.; Hagiwara R. Physicochemical Properties and Plastic Crystal Structures of Phosphonium Fluorohydrogenate Salts. Phys. Chem. Chem. Phys. 2011, 13, 12536–12544. 10.1039/c1cp20285e. [DOI] [PubMed] [Google Scholar]
  21. Zhou Z.-B.; Matsumoto H. Lithium-Doped, Organic Ionic Plastic Crystal Electrolytes Exhibiting High Ambient-Temperature Conductivities. Electrochem. Commun. 2007, 9, 1017–1022. 10.1016/j.elecom.2006.12.012. [DOI] [Google Scholar]
  22. Hayasaki T.; Hirakawa S.; Honda H. New Ionic Plastic Crystals of NR4BEt3Me (R = Me and Et) and NRxR′4–xBEt3Me (R = Et, R′ = Me and Pr, x = 1–3) in a New Class of Plastic Crystals. Bull. Chem. Soc. Jpn. 2013, 86, 993–1001. 10.1246/bcsj.20130040. [DOI] [Google Scholar]
  23. Yunis R.; Newbegin T. W.; Hollenkamp A. F.; Pringle J. M. Ionic Liquids and Plastic Crystals with a Symmetrical Pyrrolidinium Cation. Mater. Chem. Front. 2018, 2, 1207–1214. 10.1039/C8QM00016F. [DOI] [Google Scholar]
  24. MacFarlane D. R.; Huang J.; Forsyth M. Lithium-Doped Plastic Crystal Electrolytes Exhibiting Fast Ion Conduction for Secondary Batteries. Nature 1999, 402, 792–794. 10.1038/45514. [DOI] [Google Scholar]
  25. Henderson W. A.; Herstedt M.; Young V. G.; Passerini S.; De Long H. C.; Trulove P. C. New Disordering Mode for TFSI– Anions: The Nonequilibrium, Plastic Crystalline Structure of Et4NTFSI. Inorg. Chem. 2006, 45, 1412–1414. 10.1021/ic0513742. [DOI] [PubMed] [Google Scholar]
  26. Harada J. Plastic/Ferroelectric Molecular Crystals: Ferroelectric Performance in Bulk Polycrystalline Forms. APL Mater. 2021, 9, 020901 10.1063/5.0039066. [DOI] [Google Scholar]
  27. Basile A.; Hilder M.; Makhlooghiazad F.; Pozo-Gonzalo C.; MacFarlane D. R.; Howlett P. C.; Forsyth M. Ionic Liquids and Organic Ionic Plastic Crystals: Advanced Electrolytes for Safer High Performance Sodium Energy Storage Technologies. Adv. Energy Mater. 2018, 8, 1703491 10.1002/aenm.201703491. [DOI] [Google Scholar]
  28. Zhu H.; MacFarlane D. R.; Pringle J. M.; Forsyth M. Organic Ionic Plastic Crystals as Solid-State Electrolytes. Trends Chem. 2019, 1, 126–140. 10.1016/j.trechm.2019.01.002. [DOI] [Google Scholar]
  29. Yoshizawa-Fujita M.; Nakazawa M.; Takeoka Y.; Rikukawa M. Phase Transitions and Ionic Conductivity of Ionic Plastic Crystals Based on Pyrrolidinium Cations and Dihydrogen Phosphate Anion. J. Non-Cryst. Solids: X 2022, 13, 100078 10.1016/j.nocx.2021.100078. [DOI] [Google Scholar]
  30. Su Y.; Liu G.; Xie B.; Fu D.; Wang D. Crystallization Features of Normal Alkanes in Confined Geometry. Acc. Chem. Res. 2014, 47, 192–201. 10.1021/ar400116c. [DOI] [PubMed] [Google Scholar]
  31. Shimizu T.; Tanaka S.; Onoda-Yamamuro N.; Ishimaru S.; Ikeda R. New Rotator Phase Revealed in Di-n-Alkylammonium Bromides Studied by Solid-State NMR, Powder XRD, Electrical Conductivity and Thermal Measurements. J. Chem. Soc., Faraday Trans. 1997, 93, 321–326. 10.1039/a605760h. [DOI] [Google Scholar]
  32. Pringle J. M.; Shekibi Y.; MacFarlane D. R.; Forsyth M. The Influence of Different Nanoparticles on a Range of Organic Ionic Plastic Crystals. Electrochim. Acta 2010, 55, 8847–8854. 10.1016/j.electacta.2010.08.027. [DOI] [Google Scholar]
  33. Yamada Y.; Kashimoto E.; Honda H. New Chemical Family of [n-CxH(2x+1)NEt3][BEt3Me] Showing Ionic Plastic-Crystal (x = 4, 5), Rotator-Crystal (x = 6, 7) and Liquid-Crystal Phases (x = 8–16). Bull. Chem. Soc. Jpn. 2019, 92, 1289–1298. 10.1246/bcsj.20190085. [DOI] [Google Scholar]
  34. Green M.; Kuc T. A. Cationic Transition-Metal Complexes. Part II. The Reaction of Arenes and Olefins with Bis(cyclo-octa-1,5-diene or Norbornadiene)Rhodium Tetrafluoroborate. J. Chem. Soc., Dalton Trans. 1972, 832–839. 10.1039/dt9720000832. [DOI] [Google Scholar]
  35. RajanBabu T. V.; Ayers T. A.; Halliday G. A.; You K. K.; Calabrese J. C. Carbohydrate Phosphinites as Practical Ligands in Asymmetric Catalysis: Electronic Effects and Dependence of Backbone Chirality in Rh-Catalyzed Asymmetric Hydrogenations Synthesis of R- or S-Amino Acids Using Natural Sugars as Ligand Precursors. J. Org. Chem. 1997, 62, 6012–6028. 10.1021/jo970884d. [DOI] [Google Scholar]
  36. Song G.; Zhang Y.; Su Y.; Deng W.; Han K.; Li X. Pyridine-Based N-Heterocyclic Carbene Hydride Complexes of Iridium via C–H Activation. Organometallics 2008, 27, 6193–6201. 10.1021/om800756c. [DOI] [Google Scholar]
  37. Kar M.; Matuszek K.; MacFarlane D. R.. Ionic Liquids. In Kirk-Othmer Encyclopedia of Chemical Technology; John Wiley & Sons, Inc.: Hoboken, 2019. [Google Scholar]
  38. Sas O. G.; Domínguez I.; González B.; Domínguez Á. Liquid-Liquid Extraction of Phenolic Compounds from Water Using Ionic Liquids: Literature Review and New Experimental Data Using [C2mim]FSI. J. Environ. Manage. 2018, 228, 475–482. 10.1016/j.jenvman.2018.09.042. [DOI] [PubMed] [Google Scholar]
  39. Weller A. S.; Mahon M. F.; Steed J. W. Rhodium Cyclooctadiene Complexes of the Weakly Co-Ordinating Carborane Anion [Closo-CB11H12]−. Isolation and Crystal Structures of [(COD)Rh(η2-CB11H12)] and [(COD)Rh(THF)2][CB11H12]. J. Organomet. Chem. 2000, 614–615, 113–119. 10.1016/S0022-328X(00)00608-2. [DOI] [Google Scholar]
  40. Tang Y.; Yu B. Coinage Metal (Bisfluorosulfonyl)Imide Complexes: Preparation, Characterization, and Catalytic Applications. Eur. J. Inorg. Chem. 2020, 2020, 107–118. 10.1002/ejic.201901058. [DOI] [Google Scholar]
  41. Polyakov O. G.; Ivanova S. M.; Gaudinski C. M.; Miller S. M.; Anderson O. P.; Strauss S. H. Cu(CO)2(N(SO2CF3)2). The First Structurally Characterized Copper(I) Polycarbonyl. Organometallics 1999, 18, 3769–3771. 10.1021/om990196f. [DOI] [Google Scholar]
  42. Begley M. J.; Sowerby D. B.; Verma R. D.; Vig A. Structure of the Silver Imidodi(sulphuryl fluoride)-Benzene Solvate AgN(SO2F)2·C6H6. J. Organomet. Chem. 1994, 481, 243–246. 10.1016/0022-328X(94)85032-1. [DOI] [Google Scholar]
  43. Xiao J.; Cui Y.; Li C.; Xu H.; Zhai Y.; Zhang X.; Ma S. Room Temperature Allenation of Terminal Alkynes with Aldehydes. Angew. Chem., Int. Ed. 2021, 60, 25708–25713. 10.1002/anie.202109879. [DOI] [PubMed] [Google Scholar]
  44. Bowring M. A.; Bergman R. G.; Tilley T. D. Pt-Catalyzed C–C Activation Induced by C–H Activation. J. Am. Chem. Soc. 2013, 135, 13121–13128. 10.1021/ja406260j. [DOI] [PubMed] [Google Scholar]
  45. Sievert A. C.; Muetterties E. L. Arene Transition-Metal Chemistry. 5. Arene Ligand Exchange and Reactivity in η6-Arene Iridium(I) Complexes. Inorg. Chem. 1981, 20, 489–501. 10.1021/ic50216a034. [DOI] [Google Scholar]
  46. Guzel B.; Omary M. A.; Fackler J. P.; Akgerman A. Synthesis and Characterization of {[(COD)Rh(bis-(2R,3R)-2,5-diethylphospholanobenzene)]+BARF–} for Use in Homogeneous Catalysis in Supercritical Carbon Dioxide. Inorg. Chim. Acta 2001, 325, 45–50. 10.1016/S0020-1693(01)00601-6. [DOI] [Google Scholar]
  47. Green M.; Kuc T. A.; Taylor S. H. Cationic Transition-Metal Complexes. Part I. Synthesis and Reactions of Bis(diene)-Rhodium and -Iridium Tetrafluoroborates. J. Chem. Soc. A 1971, 2334–2337. 10.1039/j19710002334. [DOI] [Google Scholar]
  48. Mingos D. M. P.; Rohl A. L. Size and Shape Characteristics of Inorganic Molecules and Ions and Their Relevance to Molecular Packing Problems. J. Chem. Soc., Dalton Trans. 1991, 3419–3425. 10.1039/dt9910003419. [DOI] [Google Scholar]
  49. Atkins P.; Overton T.. Shriver and Atkins’ Inorganic Chemistry; Oxford University Press: New York, 2010. [Google Scholar]
  50. Dahlenburg L.; Osthoff N.; Heinemann F. W. Bis(η4-Cyclo-octa-1,5-Diene)Rhodium(I) Trifluoromethanesulfonate. Acta Crystallogr., Sect. E: Struct. Rep. Online 2001, 57, 117–118. 10.1107/S1600536801003208. [DOI] [Google Scholar]
  51. Baenziger N. C.; Mottel E. A.; Doyle J. R. Structure of Bis(1,5-cyclooctadiene)rhodium(I) Hexacarbonyl-tri-μ-chloro-dirhenate(I). Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 1991, 47, 539–541. 10.1107/S0108270190009507. [DOI] [Google Scholar]
  52. Kotani Y.; Honda H. 1H and 13C NMR Studies on New Ionic Plastic Crystals Constructed by Ellipsoidal Cations with [BEt3Me] Anion. Bull. Chem. Soc. Jpn. 2019, 92, 768–778. 10.1246/bcsj.20180320. [DOI] [Google Scholar]
  53. Rice D. M.; Wittebort R. J.; Griffin R. G.; Meirovitch E.; Stimson E. R.; Meinwald Y. C.; Freed J. H.; Scheraga H. A. Rotational Jumps of the Tyrosine Side Chain in Crystalline Enkephalin. 2H NMR Line Shapes for Aromatic Ring Motions in Solids. J. Am. Chem. Soc. 1981, 103, 7707–7710. 10.1021/ja00416a002. [DOI] [Google Scholar]
  54. Emsley J. W.; Lindon J. C.; Tabony J. Measurement of Deuterium Quadrupole Coupling Constants of CD3 Groups by 1H–{2H} N.M.R. Studies of Nematic Solutions. Mol. Phys. 1973, 26, 1499–1509. 10.1080/00268977300102651. [DOI] [Google Scholar]
  55. Kimata H.; Sumitani R.; Mochida T. Phase Transitions and Crystal Structures of Ionic Plastic Crystals Comprising Quaternary Ammonium Cations and Carborane Anion. Chem. Lett. 2019, 48, 859–862. 10.1246/cl.190309. [DOI] [Google Scholar]
  56. Sumitani R.; Funasako Y.; Mochida T. Thermal Properties and Crystal Structures of Ruthenium-Containing Photoreactive Ionic Liquids with Short Substituents. J. Mol. Liq. 2020, 318, 114071 10.1016/j.molliq.2020.114071. [DOI] [Google Scholar]
  57. Matsumoto K.; Oka T.; Nohira T.; Hagiwara R. Polymorphism of Alkali Bis(fluorosulfonyl)amides (M[N(SO2F)2], M = Na, K, and Cs). Inorg. Chem. 2013, 52, 568–576. 10.1021/ic3010486. [DOI] [PubMed] [Google Scholar]
  58. Mochida T.; Funasako Y.; Inagaki T.; Li M.-J.; Asahara K.; Kuwahara D. Crystal Structures and Phase-Transition Dynamics of Cobaltocenium Salts with Bis(perfluoroalkylsulfonyl)amide Anions: Remarkable Odd-Even Effect of the Fluorocarbon Chains in the Anion. Chem. −Eur. J. 2013, 19, 6257–6264. 10.1002/chem.201300186. [DOI] [PubMed] [Google Scholar]
  59. Sumitani R.; Mochida T. Thermal Properties, Crystal Structures, and Photoreactivity of Ru-Containing Ionic Liquids with Sulfur-Containing Substituents. J. Mol. Liq. 2021, 344, 117784 10.1016/j.molliq.2021.117784. [DOI] [Google Scholar]
  60. de Bruin B.; Brands J. A.; Donners J. J. J. M.; Donners M. P. J.; de Gelder R.; Smits J. M. M.; Gal A. W.; Spek A. L. Selective Oxidation of [RhI(cod)]+ by H2O2 and O2. Chem. −Eur. J. 1999, 5, 2921–2936. . [DOI] [Google Scholar]
  61. de Bruin B.; Boerakker M. J.; Donners J. J. J. M.; Christiaans B. E. C.; Schlebos P. P. J.; de Gelder R.; Smits J. M. M.; Spek A. L.; Gal A. W. Oxidation of RhI(olefin) Fragments to 2-Rhoda(III)Oxetanes. Angew. Chem., Int. Ed. 1997, 36, 2064–2067. 10.1002/anie.199720641. [DOI] [Google Scholar]
  62. Fernandez-Bartolome E.; Martinez-Martinez A.; Resines-Urien E.; Piñeiro-Lopez L.; Costa J. S. Reversible Single-Crystal-to-Single-Crystal Transformations in Coordination Compounds Induced by External Stimuli. Coord. Chem. Rev. 2022, 452, 214281 10.1016/j.ccr.2021.214281. [DOI] [Google Scholar]
  63. Braga D.; Maini L.; Grepioni F. Mechanochemical Preparation of Co-Crystals. Chem. Soc. Rev. 2013, 42, 7638–7648. 10.1039/c3cs60014a. [DOI] [PubMed] [Google Scholar]
  64. Green M.; Kuc T. A.; Taylor S. H. The Synthesis and Some Reactions of Bis(acetonitrile)(diene)-Rhodium and -Iridium Tetrafluoroborate. J. Chem. Soc., Dalton Trans. 1970, 1553–1554. 10.1039/c29700001553. [DOI] [Google Scholar]
  65. Tiripicchio A.; Camellini M. T.; Claver C.; Ruiz A.; Oro L. A. Diolefin Cationic Rhodium Complexes with Sulfur Donors. X-Ray Structure of [Rh(NBD)2(SEt2)]ClO4. J. Organomet. Chem. 1983, 241, 77–86. 10.1016/0022-328X(83)80027-8. [DOI] [Google Scholar]
  66. Dorta R.; Rozenberg H.; Shimon L. J. W.; Milstein D. Dimethylsulfoxide as a Ligand for RhI and IrI Complexes—Isolation, Structure, and Reactivity towards X-H Bonds (X = H, OH, OCH3). Chem.–Eur. J. 2003, 9, 5237–5249. 10.1002/chem.200305144. [DOI] [PubMed] [Google Scholar]
  67. Bats J. W.; Rivas Nass A.; Hashmi A. S. K. Low-Temperature Phase of Diaqua(1,5-cyclooctadiene)rhodium(I) Trifluoromethanesulfonate. Acta Crystallogr., Sect. E: Struct. Rep. Online 2004, 60, 85–87. [Google Scholar]
  68. Schenck T. G.; Downes J. M.; Milne C. R. C.; Mackenzie P. B.; Boucher T. G.; Whelan J.; Bosnich B. Bimetallic Reactivity. Synthesis of Bimetallic Complexes Containing a Bis(phosphino)pyrazole Ligand. Inorg. Chem. 1985, 24, 2334–2337. 10.1021/ic00209a003. [DOI] [Google Scholar]
  69. Shelly K.; Finster D. C.; Lee Y. J.; Scheidt W. R.; Reed C. A. η1-Benzene Coordination: The Synthesis and X-Ray Crystal Structure of a Novel Silver Salt of the Weakly Coordinating Carborane Anion B11CH12–. J. Am. Chem. Soc. 1985, 107, 5955–5959. 10.1021/ja00307a021. [DOI] [Google Scholar]
  70. Davis J. H.; Jeffrey K. R.; Bloom M.; Valic M. I.; Higgs T. P. Quadrupolar Echo Deuteron Magnetic Resonance Spectroscopy in Ordered Hydrocarbon Chains. Chem. Phys. Lett. 1976, 42, 390–394. 10.1016/0009-2614(76)80392-2. [DOI] [Google Scholar]
  71. Sheldrick G. M. A Short History of SHELX. Acta Crystallogr., Sect. A: Found. Crystallogr. 2008, 64, 112–122. 10.1107/S0108767307043930. [DOI] [PubMed] [Google Scholar]
  72. APEX3, v2015.52; Bruker AXS Inc.: Madison, WI, 2015. [Google Scholar]
  73. Macrae C. F.; Bruno I. J.; Chisholm J. A.; Edgington P. R.; McCabe P.; Pidcock E.; Rodriguez-Monge L.; Taylor R.; van de Streek J.; Wood P. A. Mercury CSD 2.0 – New Features for the Visualization and Investigation of Crystal Structures. J. Appl. Crystallogr. 2008, 41, 466–470. 10.1107/S0021889807067908. [DOI] [Google Scholar]
  74. Spek A. L. Structure Validation in Chemical Crystallography. Acta Crystallogr., Sect. D: Biol. Crystallogr. 2009, 65, 148–155. 10.1107/S090744490804362X. [DOI] [PMC free article] [PubMed] [Google Scholar]
  75. Sheldrick G. M.TWINABS v2012/1; University of Göttingen, 2012. [Google Scholar]
  76. XPREP v2014/2; Bruker AXS Inc.: Madison, WI, 2014. [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

ic2c03865_si_001.pdf (944.7KB, pdf)

Articles from Inorganic Chemistry are provided here courtesy of American Chemical Society

RESOURCES