Skip to main content
NCBI home page
ACS AuthorChoice logoLink to ACS AuthorChoice
. 2022 Oct 12;61(42):16905–16913. doi: 10.1021/acs.inorgchem.2c02949

Neutral and Cationic Complexes of Silicon(IV) Halides with Phosphine Ligands

Rhys P King 1, John M Dyke 1, William Levason 1, Gillian Reid 1,*
PMCID: PMC9597660  PMID: 36222839

Abstract

graphic file with name ic2c02949_0010.jpg

The reaction of SiI4 and PMe3 in n-hexane produced the yellow salt, [SiI3(PMe3)2]I, confirmed from its X-ray structure, containing a trigonal bipyramidal cation with trans-phosphines. This contrasts with the six-coordination found in (the known) trans-[SiX4(PMe3)2] (X = Cl, Br) complexes. The diphosphines o-C6H4(PMe2)2 and Et2P(CH2)2PEt2 form six-coordinate cis-[SiI4(diphosphine)], which were also characterized by X-ray crystallography, multinuclear NMR, and IR spectroscopy. Reaction of trans-[SiX4(PMe3)2] (X = Cl, Br) with Na[BArF] (BArF = [B{3,5-(CF3)2C6H3}4]) produced five-coordinate [SiX3(PMe3)2][BArF], but while Me3SiO3SCF3 also abstracted chloride from trans-[SiCl4(PMe3)2], the reaction products were six-coordinate complexes [SiCl3(PMe3)2(OTf)] and [SiCl2(PMe3)2(OTf)2] with the triflate coordinated. X-ray crystal structures were obtained for [SiCl3(PMe3)2][BArF] and [SiCl2(PMe3)2(OTf)2]. The charge distribution across the silicon species was also examined by natural bond orbital (NBO) analyses of the computed density functional theory (DFT) wavefunctions. For the [SiX4(PMe3)2] and [SiX3(PMe3)2]+ complexes, the positive charge on Si decreases and the negative charge on X decreases going from X = F to X = I. Upon going from [SiX4(PMe3)2] to [SiX3(PMe3)2]+, i.e., removal of X–, there is an increase in positive charge on Si and a decrease in negative charge on the X centers (except for the case X = F). The positive charge on P shows a slight decrease.

Short abstract

Unusual neutral and monocationic silicon(IV) iodide complexes with soft phosphine coordination are formed in hydrocarbon solvents, while treatment of [SiCl4(PMe3)2] with NaBArF forms the [SiCl3(PMe3)2]+ cation; the electronic structures of [SiX4(PMe3)2] and [SiX3(PMe3)2]+ (X = F, Cl, Br, I) are probed using DFT calculations.

Introduction

In marked contrast to its lighter congener (carbon), silicon forms many compounds in which the silicon center is five- or six-coordinate. These hypervalent silicon(IV) compounds, that is, compounds in which the silicon center formally exceeds eight electrons in its outer shell, have remained a very active research area for over a century and range from organosilicon species1 to inorganic silicon anions such as [SiF5]−, [SiF6]2–,2 and [Si(OTf)6]2– (OTf– = CF3SO3–),3 to complexes with bi- or poly-dentate anionic N- or O-donor ligands.4 Silicon(IV) halides form many hypervalent adducts with Lewis bases, including both neutral and cationic species, the majority containing neutral N- (amine, N-heterocycles, etc.) or O-donor (ethers, pnictogen oxides, etc.) ligands.2 Significant recent attention has focused on N-heterocyclic carbene (NHC) adducts of SiX4 (X = F, Cl, or Br), which, in addition to their high stability, can be reduced under appropriate conditions to generate rare examples of stable solid Si(II) compounds and even in some examples giving formally Si(I) or Si(0) species.5 Heterocyclic silylenes (Si(II) species) have also been described.5

Although only one example of displacement of fluoride from SiF4 by a neutral ligand is known, in [SiF3(Me3-tacn)][SiF5] (Me3-tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane),6 silicon(IV) cations containing the heavier halogens have been known for over 50 years, typical examples being [SiCl2(2,2′-bipy)2]Cl2, [Si(2,2′-bipy)3]I4, [SiI2(py)4]I2, and [SiCl2(L)2]Cl2 (L = N-methylimidazole).2 More recent studies have reported complexes such as mer- and fac-[SiCl3(hmpa)3]+ and [SiCl3(hmpa)2]+ (hmpa = hexamethylphosphoramide),7 [SiCl3(Me3-tacn)][OTf] (OTf = CF3SO3), and [SiX3(pmdta)][BArF] (X = Cl, Br; pmdta = Me2N(CH2)2N(Me)(CH2)2NMe2; BArF = [B{3,5-(CF3)2C6H3}4]).8 The reaction of the carbene, 1,3-dimethylimidazolidin-2-ylidene (NHC1), with SiCl4 forms the 1:1 adduct, [SiCl4(NHC1)], which reacts with the electron-deficient silane, H2Si(C2F5)2, to generate the trigonal bipyramidal cation in [SiCl2H(NHC1)2][SiCl3(C2F5)2], and with BCl3 forms [SiCl3(NHC1)][BCl4], containing a tetracoordinate cation. The latter reacts with further [SiCl4(NHC1)] to give the trigonal bipyramidal [SiCl3(NHC1)2][BCl4].9 1,2-Bis(2,6-di-isopropylphenyl)imidazole-2-ylidene, (NHC2), displaces one of the halides from the silicon center to form [SiX3(NHC2)][X] (X = Br, I), which can be reduced with KC8 to form the neutral Si(II) species [SiX2(NHC2)]. [SiI2(NHC2)] can be reacted further with NHC3 (NHC3 = 1,3,4,5-tetramethyl-imidazol-2-ylidene) to form [Si(NHC3)3][I]2 featuring a very unusual Si(II) dication.10

Surprisingly, little work on phosphine complexes of silicon halides has been reported (and there are no known arsine adducts).11 Early work produced [SiX4(PMe3)2] (X = Cl or Br), by reaction of the constituents at low temperatures, which were identified by vibrational spectroscopy as trans isomers and confirmed by a low-precision X-ray crystal structure of the chloride.12 No complexation occurred between SiF4 and PMe3 at ambient temperatures, but tensiometric and Raman studies suggested both 1:1 and 1:2 adducts formed at low temperature (198 K), although neither was obtained pure.12 The preparation of [SiCl3(PMe3)2][ClO4] was also reported, but with minimal characterization.12 No further studies of these complexes were reported until our investigation13 of the reaction of SiF4 with a range of phosphine and diphosphine ligands, which found no evidence for adduct formation at ambient temperatures in the absence of a solvent, or in solution down to 180 K. However, detailed characterizations of trans-[SiX4(PMe3)2] (X = Cl, Br) were reported, although attempts to isolate the corresponding complexes of SiI4 from CH2Cl2 solution were unsuccessful.14

Diphosphines o-C6H4(PMe2)2 and R2P(CH2)2PR2 (R = Me, Et) also reacted with SiCl4 and SiBr4 to form cis-[SiX4(diphosphine)] as stable complexes, while the reaction of SiCl4 with the methylene-linked Me2PCH2PMe2 formed trans-[SiCl4(κ1-Me2PCH2PMe2)2], irrespective of the reactant ratio used. The first example of a phosphine complex of a halosilane, [SiHCl3{Et2P(CH2)2PEt2}], has also been characterized, although PMe3 and other diphosphines caused disproportionation into the SiCl4 adducts.14 Despite considerable efforts, the reaction of [SiCl4(PR3)2] or cis-[SiX4(diphosphine)] with reducing agents including KC8, K, sodium naphthalide, and [(DiPPNacNac)Mg]2 (DiPPNacNac = Ar*NC(Me)CHC(Me)NAr*; Ar* = 2,6-iPr2-C6H3) did not lead to the isolation of Si(II) phosphine adducts.14

We report here the preparation and spectroscopic and structural characterization of several neutral and cationic complexes of silicon(IV) iodide with phosphine ligands, together with synthesis of the corresponding cations derived from chloride abstraction from silicon(IV) chloride phosphine species. Density functional theory (DFT) calculations with natural bond orbital (NBO) analysis are used to probe their electronic structures, relative energies of the frontier orbitals and the charge distributions.

Results and Discussion

Silicon Iodide Complexes

As noted above, although trans-[SiX4(PMe3)2] (X = Cl, Br) are readily made from SiX4 and PMe3 in anhydrous CH2Cl2, similar reactions using SiI4 did not yield the analogous iodide complex.14 However, mixing solutions of SiI4 and PMe3 in anhydrous n-hexane or n-pentane (Scheme 1) produced an immediate yellow precipitate of empirical formula SiI4(PMe3)2. Yellow, very moisture sensitive crystals were obtained from a CH2Cl2 solution layered with n-hexane and, in contrast to the known six-coordinate trans-[SiX4(PMe3)2],14 were found to contain a trigonal bipyramidal cation with axial phosphines with an iodide counteranion, i.e., [SiI3(PMe3)2]I (Figure 1). The crystallographically equivalent Si–P bonds are slightly longer than the bond lengths in the tetrahalide complexes [SiX4(PMe3)2] (X = Cl, Br),14 which probably reflects the weaker Lewis acidity of silicon iodide compared to the lighter halides, despite the positive charge in the monocation.

Scheme 1. Reaction of SiI4 with Monodentate and Bidentate Phosphines.

Scheme 1

Open in a new tab

Figure 1.

Figure 1

Open in a new tab

(a) Structure of the molecular cation in [SiI3(Me3P)2][I]·CH2Cl2·0.5C6H14 showing the atom numbering scheme. H atoms and lattice solvent molecules are omitted for clarity. Ellipsoids are drawn at the 50% probability level. Selected bond lengths (Å) and angles (°): Si1–I1 = 2.503(4), Si1–I2 = 2.471(7), Si1–P1 = 2.380(5), I1–Si1–I1 = 120.2(3), I2–Si1–I1 = 119.92(14), P1–Si1–I1 = 90.92(10), P1–Si1–I2 = 88.2(2), P1–Si1–P1 = 176.3(4); (b) view down the c-axis showing the weak I···I interactions (purple dashes) between the [SiI3(PMe3)2]+ cations, as well as between the [SiI3(PMe3)2]+ cations and I–; (c) space-filling diagram (including the CH2Cl2 solvate) showing the channels viewed down the c-axis. Color key: orange = P, purple = I; gray = C, green = Cl; yellow = Si; (d) view down one of the channels showing the interior lining.

Within the crystal lattice, there are several long, weak intermolecular I···I interactions that fall just within the sum of the van der Waals radii (4.08 Å).15 These form a 2D network, as shown in Figure 1b, in which three [SiI3(PMe3)2]+ cations form weakly associated triangles via I···I contacts between the coordinated iodides, the shortest I···I distances being 3.933(3) Å. In addition, there are cation–anion interactions between two of the iodine atoms in each [SiI3(PMe3)2]+ unit, with two iodide counter anions, with d(I···I) = 3.6852(15) Å. These interactions lead to the formation of an extended structure containing both enclosed void cavities and two types of 1D channel, both of which are aligned down the c direction. Collectively, these account for ca. 39% of the cell volume. One set of 1D channels is filled with the CH2Cl2 solvent; these channels occur where the edges of the hexagonal units meet (see Figure 1c,d). The second type of 1D channel occurs at the center of the hexagonal unit. The enclosed void cavities contain electron density accounted for by applying a solvent mask and are attributed to the disordered n-hexane solvent (which is also present in the 1H NMR spectrum).

A strong peak in the far IR spectrum at 379 cm–1 is assigned as the E′ Si–I stretching vibration of the trigonal bipyramidal cation. The 1H NMR spectrum shows a doublet at δ = 1.66, a significant high-frequency coordination shift of +0.77 ppm, while the 31P{1H} NMR spectrum exhibits a broad singlet at δ = 3.2, a coordination shift of +65 ppm, although no silicon satellites were seen at either 293 or 180 K; 29Si satellites were observed in the 31P{1H} NMR spectrum recorded at 253 K (1JSiP = 93 Hz). However, no convincing silicon-29 resonance could be observed over the temperature range 293–180 K, possibly due to a dynamic exchange process.

The addition of either of the diphosphines, Et2P(CH2)2PEt2 and o-C6H4(PMe2)2, to a solution of SiI4 in a hydrocarbon solvent led to the immediate precipitation of orange solids in good yields, which were identified as [SiI4{Et2P(CH2)2PEt2}] and [SiI4{o-C6H4(PMe2)2}], respectively, on the basis of crystal structure determinations and microanalysis. Crystals of [SiI4(o-C6H4{PMe2}2)] were grown by layering a CH2Cl2 solution with n-hexane, while crystals of [SiI4{Et2P(CH2)2PEt2}] were obtained from slow evaporation of a CH2Cl2 solution of the complex. The structures (Figure 2) show that like their analogs with the lighter halides,14 they contain cis-octahedral molecules.

Figure 2.

Figure 2

Open in a new tab

The molecular structures of (a) [SiI4{o-C6H4(PMe2)2}]·0.5C6H14 and (b) [SiI4{Et2P(CH2)2PEt2}] showing the atom labeling schemes. Ellipsoids are drawn at the 50% probability level, and H atoms and hexane solvent are omitted for clarity. Selected bond lengths (Å) and angles (°) for (a) are Si1–P1 = 2.3707(9), Si1–P2 = 2.3678(9), Si1–l1 = 2.6812(7), Si1–l2 = 2.6326(7), Si1–l3 = 2.6267(7), Si1–l4 = 2.6371(7), P1–Si1–P2 = 86.14(3), I1–Si1–I3 = 175.81(3), and I2–Si1–I4 = 93.47(2) and (b) are Si1–P1 = 2.391(8), Si1–P2 = 2.405(7), Si1–l1 = 2.647(7), Si1–l2 = 2.631(5), Si1–l3 = 2.670(7), Si1–l4 = 2.645(6) P1–Si1–P2 = 86.6(3), I1–Si1–3 = 177.2(2), and I2–Si1–I4 = 93.29(18).

The Si–I bond distances are similar in the two [SiI4(diphosphine)] complexes, and all fall within the range of 2.6266(7)–2.6812(7) Å, i.e., elongated relative to SiI4 itself (2.43 Å),16 consistent with the higher coordination number present. The d(Si–I) values in the bidentate phosphine complexes are also ca. 0.15 Å longer than in the five-coordinate [SiI3(PMe3)2]+ cation described above (2.471(7)–2.503(4) Å) and can also be explained by the lower coordination number (less steric crowding) in the PMe3 complex, along with the presence of the positive charge strengthening the Si–I interaction. The d(Si–P) values are very similar to those in the corresponding complexes of SiX4 (X = Cl, Br).14 For [SiI4{o-C6H4(PMe2)2}] the crystal packing gives rise to a structure that contains 1D channels aligned in the a-direction (Figure 3). The electron density in these channels is consistent with there being two hexane molecules per unit cell.

Figure 3.

Figure 3

Open in a new tab

(a) Space-filling diagram of [SiI4{o-C6H4(PMe2)2}]·0.5C6H14 showing the channels viewed down the a-axis. Color key: orange = P; purple = I; gray = C; yellow = Si; (b) view down one of the channels showing the interior lining.

The 31P{1H} NMR data are shown in Table 1 along with data reported for the lighter halide analogs. Notably, the iodide complexes did not exhibit convincing 29Si NMR resonances over the temperature range 295–183 K, possibly due to dissociative anion exchange.

Table 1. 31P{1H} NMR dataa.

complex X = Cl δ(31P/ppm), (1JPSi/Hz)b X = Br δ(31P/ppm), (1JPSi/Hz)b X = I δ(31P/ppm), (1JPSi/Hz)
[SiX4{o-C6H4(PMe2)2}] –11.9, (138) –14.9, (103) –33.6, (not resolved)
[SiI4{Et2P(CH2)2PEt2}] +0.7, (134) –2.1, (99) –25.6, (not resolved)
Open in a new tab
a

CD2Cl2 solution, 298 K.

b

Ref (14)

Phosphine Complexes of Silicon(IV) Cations

Since phosphine-substituted cations of silicon(IV) chloride or bromide do not form spontaneously, the use of halide abstraction reagents, AlX3, TMSOTf (Me3SiO3SCF3), and Na[BArF], which have been used successfully to generate tin(IV) and germanium(IV) cations,17 was explored. The reactions of AlX3 with the neutral silicon phosphine complexes caused loss of phosphine to the aluminum and were not pursued. However, addition of solid Na[BArF] to a solution of [SiX4(PMe3)2] (X = Cl, Br) in anhydrous CH2Cl2 resulted in a white precipitate (NaX) (Scheme 2) and workup of the filtrate gave [SiX3(PMe3)2][BArF]. Crystals of [SiCl3(PMe3)2][BArF] were grown from a CH2Cl2 solution layered with n-hexane, and single crystal X-ray structure analysis showed it to have a trigonal bipyramidal cation (Figure 4).

Scheme 2. Reactions of [SiX4(PMe3)2] with Halide Abstraction Agents.

Scheme 2

Open in a new tab

Figure 4.

Figure 4

Open in a new tab

The molecular structure of the cation in [SiCl3(PMe3)2][BArF] showing the atom labeling scheme. Ellipsoids are drawn at the 50% probability level. H atoms and the BArF counter anion are omitted for clarity. Selected bond lengths (Å) and angles (°) are Si1–P1 = 2.3272(16), Si1–P2 = 2.3229(15), Si1–Cl1 = 2.0828(15), Si1–Cl2 = 2.0811(15), Si1–Cl3 = 2.0866(14), P1–Si1–P2 = 178.97(7), Cl1–Si1–Cl2 = 120.30(7), Cl2–Si1–Cl3 = 121.27(7), and Cl1–Si1–Cl3 = 118.42(7).

There is a small decrease in the Si–P bond length upon going from the neutral tetrachloride complex to the monocation (Table 2). This is accompanied by a substantial decrease in the Si–Cl bond distance by ca. 0.14 Å upon formation of the monocation, indicating that most of the positive charge is taken up by the SiCl3 unit.

Table 2. Selected Geometric Parameters for Silicon Halide PMe3 Complexes.

  [SiCl4(PMe3)2]14 [SiCl3(PMe3)2][BArF] [SiI3(PMe3)2][I]
d(Si–X), Å 2.2069(3) 2.0828(15) 2.503(4)
2.2296(3) 2.0811(15) 2.471(7)
  2.0866(14)  
d(Si–P), Å 2.3484(3) 2.3276(14) 2.380(5)
  2.3230(13)  
C–P–C angles, ° 104.76(5)–105.94(5) 106.4(3)–108.2(3) 104.2(7)–109.1(9)
Open in a new tab

Selected NMR data are shown in Table 3. In contrast to the silicon iodide complexes, the chloride and bromide complexes readily gave 29Si NMR spectra. In our previous study,14 we found that the available relaxation agents TEMPO (2,2,6,6-tetramethylpiperidineN-oxyl) and [Cr(acac)3] reacted with the silicon halide complexes, but in the present work, we used tris(2,2,6,6-tetramethyl-3,5-heptanedionato)chromium(III) (TMHD),7 which did not react with the silicon complexes.

Table 3. Selected Spectroscopic Data for Neutral and Cationic Silicon(IV) Phosphine Complexes.

compound 31P{1H}, ppm 29Si, ppma 1JSiP, Hz ν(Si-X), cm–1
[SiCl4(PMe3)2] 2.3 –210 257 417
[SiCl3(PMe3)2][BArF] –3.5 –105 211 527
[SiBr4(PMe3)2] –1.2 –284 227 321
[SiBr3(PMe3)2][BArF] 3.5 –140 184 433
[SiI3(PMe3)2][I] 3.2     379
Open in a new tab
a

Recorded in CD2Cl2 at 183 K using [Cr(TMHD)3] as a relaxation agent.

Finally, the reactions of the tetrahalides with TMSOTf (Me3SiO3SCF3) were also examined. The reaction of [SiCl4(PMe3)2] with one or two equivalents of TMSOTf in CH2Cl2 generated the six-coordinate complexes with coordinated triflate rather than lower coordinate cations, [SiCl3(PMe3)2(OTf)] and [SiCl2(PMe3)2(OTf)2], respectively. The same result was also found in many germanium and tin systems.17 Crystals of [SiCl2(PMe3)2(OTf)2] were grown by layering a CH2Cl2 solution with n-hexane, and the structure revealed the “all trans” six-coordinate complex shown in Figure 5. This is in contrast to the [GeF2(PMe3)2(OTf)2] analog, in which the triflates only interact weakly with the metal center and are mutually cis.17(c)

Figure 5.

Figure 5

Open in a new tab

The molecular structure of [SiCl2(PMe3)2(OTf)2] showing the atom labeling scheme. Ellipsoids are drawn at the 50% probability level, and H atoms are omitted for clarity. Selected bond lengths (Å) and angles (°) are Si1–P1 = 2.3389(6), Si1–P2 = 2.3478(6), Si1–Cl1 = 2.1880(5), Si1–Cl2 = 2.1753(5), Si1–O1 = 1.8402(11), Si1–O4 = 1.8438(11), P1–Si1–P2 = 175.49(2), Cl1–Si1–Cl2 = 178.98(3), and O1–Si1–O4 = 175.01(6).

There is a small positive shift in the 1H NMR resonance upon converting the tetrachloride to the mono- and bis-triflate derivatives. However, in the 31P{1H} spectrum, there is a negative shift to δ = −0.21 for the mono-triflate and a positive shift to δ = +3.2 for the bis-triflate. In the case of [SiCl2(PMe3)2(OTf)2], silicon satellites are observed with1JSiP = 211 Hz, smaller than for the parent tetrachloride complex.

DFT Calculations

DFT calculations using the B3LYP-D3 functional were performed on the [SiX3(PMe3)2]+ (F, Cl, Br, I) cations in order to understand their electronic structures. For [SiCl3(PMe3)2]+ and [SiI3(PMe3)2]+, whose structures have been determined crystallographically, the geometric optimizations started from the experimental geometries, while for the [SiF3(PMe3)2]+ and [SiBr3(PMe3)2]+ cations, whose X-ray structures are not known, the geometry of [SiCl3(PMe3)2]+ was used as a starting point (with the chloride exchanged for the appropriate halide) and the structures were allowed to refine and optimize. In all cases, the calculations converged with no imaginary frequencies, showing that the optimized geometries are minima on the potential energy surface. To compare with their neutral counterparts, calculations were also performed on the tetrahalide complexes, [SiX4(PMe3)2] (X = F, Cl, Br, I). For X = Cl and Br, the starting geometries were based on their published crystal structures,14 while for X = F and I, the structures were computed starting from the geometry of [SiCl4(PMe3)2] (changing the Cl to the appropriate halide).

Table 4 compares the geometric parameters from the experimental X-ray crystallographic structures and the computed geometries for the [SiCl3(PMe3)2]+ and [SiI3(PMe3)2]+ cations. There is good agreement between the two (although, of course the DFT calculations assume an isolated cation, whereas the X-ray crystallographic values are determined from the solid state and include the anion and packing effects).

Table 4. Comparison of the Computed and Experimentally Determined Geometric Parameters for [SiCl3(PMe3)2]+ and [SiI3(PMe3)2]+.

[SiCl3(PMe3)2]+ X-ray data, Å DFT (B3LYP-D3), Å [SiI3(PMe3)2]+ X-ray data, Å DFT (B3LYP-D3), Å
Si–Cl 2.0828(15) 2.12782 Si–I 2.503(4) 2.57309
2.0811(15) 2.12767   2.471(7) 2.57336
2.0866(14) 2.12785     2.57324
Si–P 2.3272(16) 2.35909 Si–P 2.380(5) 2.44975
2.3229(15) 2.35908     2.44975
Cl–Si–Cl 120.30(7) 120.03881 I–Si–I 119.92(14) 119.98383
121.27(7) 119.99066   120.2(3) 120.000888
118.42(7) 120.03881     120.01529
P–Si–P 178.97(7) 179.97953 P–Si–P 176.3(4) 179.96224
Open in a new tab

NBO analyses were performed on the computed DFT wavefunctions of the complexes to determine how the charge is distributed in the Si(IV) phosphine complexes, and the results are summarized in Table 5. In general, the positive charge on the silicon center decreases and the negative charge on X decreases upon going from F to I. The positive charge on P increases slightly. Upon going from [SiX4(PMe3)2] to [SiX3(PMe3)2]+, i.e., removal of an X– ion, there is an increase in the charge on both the silicon center and the halide centers, except for the case of X = F, where there is a small decrease in natural charge on silicon upon fluoride abstraction. There is only a moderate decrease in the charge on the phosphorus atoms, consistent with the 31P{1H} NMR shifts being similar across the halides and also with the 29Si NMR shifts being much more sensitive to the specific halide present and the charge on the complex.

Table 5. Selected NBO Charges for Atomic Centers in Complexes [SiX4(PMe3)2] and [SiX3(PMe3)2]+.

  [SiF4(PMe3)2] [SiCl4(PMe3)2] [SiBr4(PMe3)2] [SiI4(PMe3)2]
natural charge on Si 1.81 0.77 0.49 0.14
natural charge on P 1.02 1.11 1.13 1.13
natural charge on X (av.) –0.68 –0.48 –0.41 –0.31
  [SiF3(PMe3)2]+ [SiCl3(PMe3)2]+ [SiBr3(PMe3)2]+ [SiI3(PMe3)2]+
natural charge on Si 1.79 0.84 0.57 0.23
natural charge on P 1.00 1.07 1.10 1.08
natural charge on X (av.) –0.64 –0.37 –0.29 –0.14
Open in a new tab

The HOMO–LUMO gaps of the tetrahalide and cationic complexes were investigated using DFT calculations. Going down the halide group, the HOMO–LUMO gap was found to decrease, for example, the gap for the neutral tetraiodide complexes is ca. 5 eV less than the neutral tetrafluoride. Also, for each halide type, the cation has a larger gap than the tetrahalide (see Figure 6).

Figure 6.

Figure 6

Open in a new tab

Graph showing the HOMO–LUMO energy gaps for the neutral tetrahalide and monocationic trihalide cations, determined by DFT calculations.

Experimental Section

Silicon halides, PMe3, and Et2P(CH2)2PEt2 were obtained from Strem, Alfa Aesar, or Sigma-Aldrich and used as received. TMSOTf (Sigma-Aldrich) was distilled prior to use. o-C6H4(PMe2)2 was made by the literature route.18 All reactions were conducted using Schlenk, vacuum line, and glovebox techniques and under a dry dinitrogen atmosphere. CH2Cl2 was dried by distillation from CaH2 and n-hexane, n-pentane and toluene from Na, and stored over activated molecular sieves. NMR solvents were also stored over 4 Å sieves.

IR spectra were recorded as Nujol mulls between CsI plates using a Perkin Elmer Spectrum 100 spectrometer over the range of 4000–200 cm–1. NMR spectra were recorded using a Bruker AVII 400 or AVIII HD400 spectrometer. 1H NMR spectra were referenced to residual solvent resonances,19F{1H} NMR spectra to external CFCl3, 31P{1H} NMR spectra to aqueous 85% H3PO4, and 29Si NMR spectra to TMS. The latter used tris(2,2,6,6-tetramethyl-3,5-heptanedionato)chromium(III) (TMD) as a relaxation agent. Microanalytical measurements were performed by Medac Ltd.

X-Ray Crystallography

Single crystals were grown as described. Single-crystal X-ray data were collected using a Rigaku AFC12 goniometer equipped with an enhanced-sensitivity (HG) Saturn724+ detector mounted at the window of an FR-E+ SuperBright molybdenum (λ = 0.71073 Å) rotating anode generator with VHF or HF Varimax optics (70 or 100 μm focus), with the crystal held at 100 K (N2 Cryostream). Structure refinements were performed with either SHELX(S/L)97 or SHELX(S/L)2013, through Olex22519 and were mostly straightforward, with H atoms bonding to C atoms placed in calculated positions using default C–H distances. Where additional constraints or restraints were required, details are provided in the cif file for each structure. For [SiI4{Et2P(CH2)2PEt2}], the crystal was twinned, and the structure was refined against a deconvoluted data set. For [SiI3(PMe3)2][I], there were alerts due to residual election density near the iodine atoms, most likely due to absorption, as well as some residual disordered solvent in the central channel, which could not be accounted for by applying a mask. CCDC reference numbers for the crystallographic information files in cif format are [SiI4{Et2P(CH2)2PEt2}] 2162654, [SiI4{o-C6H4(PMe2)2}] 2162655, [SiCl3(PMe3)2][BArF] 2162656, [SiI3(PMe3)2][I] 2162657, and [SiCl2(PMe3)2(OTf)2] 2162658.

The structure of [SiI3(PMe3)2][I]·CH2Cl2·0.5C6H14 shows channels through the extended lattice. The residual electron density within the enclosed voids is attributed to disordered n-hexane, which could not be satisfactorily modeled, so a solvent mask was used. For this structure, there are 150e- unaccounted for in two enclosed voids of 210.7 Å3, which is consistent with three n-hexane molecules per unit cell (the second type of channel voids corresponds to a volume 426 Å3 per unit cell and is empty). Similarly, for the structure of [SiI4{o-C6H4(PMe2)2}]·0.5C6H14, there are channels through the extended lattice, which also appear to contain disordered n-hexane. For this structure, there are 100e- unaccounted for in a void of 250 Å3, which is consistent with two n-hexane molecules per unit cell. A solvent mask was also used here. For [SiI4(PEt2{CH2}2PEt2)], the crystal was twinned and the resulting structure was refined against deconvoluted data from a single component.

Complex Syntheses

[SiI3(PMe3)2][I]

SiI4 (0.500 g, 0.99 mmol) was dissolved n-hexane (5 mL), and to this, PMe3 (0.142 g, 1.85 mmol) was added as a solution in n-hexane (3 mL), causing a yellow powder to precipitate immediately. The reaction mixture was stirred for 1 h. The supernatant was filtered away, and the solid was washed with n-hexane (3 × 10 mL) and dried in vacuo to yield a yellow solid, with yield of 0.478 g (75%). Crystals of this complex suitable for X-ray crystallography were grown by layering a CH2Cl2 solution of the complex with n-hexane. The complex can also be isolated using n-pentane as solvent. Multiple attempts to obtain a good microanalysis on samples of this complex were unsuccessful due to the presence of varying amounts of n-hexane, which was also evident in the 1H NMR spectrum and in the X-ray crystal structure. Anal. Calc. for C6H18I4P2Si·1/4C6H14 (709.40): C, 12.7; H, 3.1. Found: C, 11.8; H, 3.6%. IR (Nujol/cm–1): ν = 379 s (Si–I). 1H NMR (CD2Cl2, 298 K): δ = 1.66 (d,1JPH = 11 Hz, CH3). 31P{1H} NMR (CD2Cl2, 298 K): δ = 3.2 (br s); (253 K): δ = 4.6 (s,1JSiP = 93 Hz). 29Si NMR (CD2Cl2, 253 K): a weak and poorly resolved triplet tentatively assigned to the complex was observed at −233 ppm.

[SiI4{o-C6H4(PMe2)2}]

SiI4 (0.150 g, 0.28 mmol) was dissolved in n-hexane. To this, o-C6H4(PMe2)2 (0.055 g, 0.28 mmol) was added as a solution in n-hexane (3 mL), causing immediate precipitation of an orange powder. The reaction mixture was stirred for 1 h. The supernatant was filtered away, and the solid was washed with n-hexane (3 × 10 mL) and dried in vacuo to yield an orange solid, with yield of 0.173 g (85%). Crystals of this complex suitable for single crystal X-ray analysis were grown by layering a CH2Cl2 solution of the complex with n-hexane. The complex can also be synthesized using n-pentane as solvent. Anal. Calc. for C10H16I4P2Si·1/2C5H12 (769.94): C, 19.5; H, 2.9 Found: C, 19.3; H, 2.7%. IR (Nujol/cm–1): ν = 281 m, 310 m (Si–I) 1H NMR (CD2Cl2, 298 K): δ = 1.99 (m, [12H], CH3), 7.69–7.90 (m, [4H], ArH). 31P{1H} NMR (CD2Cl2, 298 K): δ = −33.6 (br s,1JSiP = not resolved); (253 K): δ = −32.1 (br,1JSiP not resolved). 29Si NMR (CD2Cl2, 298/253 K): not observed.

[SiI4{Et2P(CH2)2PEt2}]

SiI4 (0.300 g, 5.60 mmol) was dissolved in toluene (5 mL); to this, Et2P(CH2)2PEt2 (0.116 g, 5.62 mmol) was added as a solution in toluene (2 mL), causing the precipitation of an orange solid. The reaction was stirred for 1 h. The supernatant was filtered away, and the solid was washed with n-hexane (3 × 10 mL) and dried in vacuo to yield an orange solid. Crystals of the complex were grown by layering a CH2Cl2 solution of the complex with n-hexane. The complex can also be synthesized using n-pentane as solvent. Yield: 0.233 g (56%). Anal. Calc. for C10H24I4P2Si·1/2C5H12 (778): C, 19.3; H, 3.9. Found: C, 19.2; H, 4.3%. IR (Nujol/cm–1): ν = 278 m, 305 m (Si–I). 1H NMR (CD2Cl2, 298 K): δ = 1.41 (m, [12H], CH3), 1.98 (m, [4H], CH2), 2.36 (br m, [8H], CH2). 31P{1H} NMR (CD2Cl2, 298 K): δ = −25.6 (br s); (183 K): δ = −20.8 (br, s). 29Si NMR (CD2Cl2, 183 K): a weak and poorly resolved triplet tentatively assigned to this complex was observed at −696 ppm.

[SiCl3(PMe3)2][BArF]

[SiCl4(PMe3)2] (0.200 g, 0.62 mmol) was dissolved in CH2Cl2 (5 mL), and Na[BArF] (0.550 g, 0.62 mmol) was added as a solid. The reaction mixture was stirred for 1 h during which a small amount of white precipitate formed (NaCl). The supernatant was filtered away and concentrated in vacuo to yield a white solid. Crystals of the complex were grown by layering a CH2Cl2 solution of the complex with n-hexane. Yield: 0.492 g (69%). Anal. Calc. for C38H30BCl3F24P2Si (1149.73): C, 39.7; H, 2.6. Found: C, 39.7; H, 3.1%. IR (Nujol/cm–1): ν = 527 s (Si–Cl).1H NMR (CD2Cl2, 298 K): δ = 1.60 (m, [18H], CH3), 7.57 (s, [4H], ArH), 7.73 (s, [8H], ArH). 31P{1H} NMR (CD2Cl2, 298 K): δ = −3.5 (1JSiP = 211 Hz); (183 K): δ = −2.4 (1JSiP = 211 Hz). 29Si NMR (CD2Cl2, 298 K): δ = −104 (t,1JSiP = 211 Hz); (183 K): −105 (t,1JSiP = 211 Hz).

[SiBr3(PMe3)2][BArF]

[SiBr4(PMe3)2] (0.100 g, 0.20 mmol) was dissolved in CH2Cl2 (5 mL) to which Na[BArF] (0.177 g, 0.20 mmol) was added as a solid, and the reaction mixture was stirred for 1 h, during which a small amount of white precipitate formed, which was removed by filtration (NaBr). The supernatant was concentrated in vacuo to yield a white solid. Yield: 0.233 g (91%). Anal. Calc. for C38H30BBr3F24P2Si (1283.11): C, 35.6; H, 2.4. Found: C, 35.8; H, 2.7%. IR (Nujol/cm–1): 433 s (Si–Br). 1H NMR (CD2Cl2, 298 K): δ = 1.62 (m, [18H], CH3), 7.57 (s, [4H], ArH), 7.73 (s, [8H], Ar–H). 31P{1H} NMR (CD2Cl2, 298 K): δ = +3.5 (br s); (183 K): δ = +6.3 (s,1JSiP = 184 Hz). 29Si NMR (CD2Cl2, 298 K): not observed; (183 K): −140 (t,1JSiP = 184 Hz).

[SiCl3(PMe3)2(OTf)]

[SiCl4(PMe3)2] (0.100 g, 0.31 mmol) was dissolved in CH2Cl2 (5 mL), and TMSOTf (0.069, 0.31 mmol) was added as a solution in CH2Cl2 (2 mL), resulting in a colorless solution. The reaction was stirred for 1 h, after which the volatiles were removed in vacuo to yield a white solid, which was washed with n-hexane (3 × 10 mL) and dried in vacuo. Yield 0.119 g (88%). Anal. Calc. for C7H18Cl3F3O3P2SSi (435.63): C, 19.3; H, 4.2. Found: C 19.3; H, 4.4%. IR (Nujol/cm–1): ν = 383 m, 423 m (Si–Cl). 1H NMR (CD2Cl2, 298 K): δ = 1.67 (d,2JPH = 12 Hz, CH3). 31P{1H} NMR (CD2Cl2, 298 K): δ = −0.21 (s,1JSiP = 248 Hz). 29Si NMR (CD2Cl2, 298 K): −146 (t,1JSiP = 248 Hz).

[SiCl2(PMe3)2(OTf)2]

[SiCl4(PMe3)2] (0.200 g, 0.62 mmol) was dissolved in CH2Cl2 (5 mL) to which TMSOTf (0.216 g, 1.24 mmol) was added as a solution in CH2Cl2 (2 mL), resulting in a colorless solution. The reaction was stirred for 1 h, and the reaction mixture was layered with n-hexane (10 mL) and stored at −18 °C, which after 1 day afforded a crop of colorless crystals, which were collected by filtration, washed with hexane (3 × 10 mL), and dried in vacuo. Yield: 0.231 g (68%). Anal. Calc. for C8H18Cl2F6O6P2S2Si·1/4C6H14 (570.79): C, 20.0; H, 3.8. Found: C, 19.6; H, 4.2%. IR (Nujol/cm–1): 442 m, 462 m (Si–Cl). 1H NMR (CD2Cl2, 298 K): δ = 1.67 (d,2JPH = 12 Hz, CH3). 31P{1H} NMR (CD2Cl2, 298 K): δ = 3.2 (s,1JSiP = 311 Hz). 29Si NMR (CD2Cl2, 298 K): −194 (t,1JSiP = 311 Hz).

DFT Computational Details

The electronic structures of the isolated molecules/cations were investigated using DFT calculations using the Gaussian 16 W software package.20 The density functional chosen was B3LYP-D3,21 corrected for dispersion,20 using the basis set 6-311G(d)22 for all atoms, except for the heavy Br and I atoms, where the pseudo-potential Lanl2dz basis sets were used (with the previously mentioned basis set used for the lighter atoms).23 For [SiCl4(PMe3)2], [SiBr4(PMe3)2], [SiI3(PMe3)2]+, and [SiCl3(PMe3)2]+, the initial geometries were taken from their crystal structures; prior to geometry optimization For [SiF4(PMe3)2] and [SiI4(PMe3)2], the structure of the complex [SiCl4(PMe3)2] was chosen as the starting geometry, with the halide atoms exchanged as appropriate. For [SiF3(PMe3)2]+ and [SiBr3(PMe3)2]+, the [SiCl3(PMe3)2]+ cation was chosen as the starting geometry with the halide atoms exchanged as appropriate. In all cases, the geometry optimization converged to a stable geometry with no imaginary frequencies. For the complexes with known X-ray crystal structures, the DFT-computed geometries were compared with the crystallographic geometries and were found to be in good agreement.

Conclusions

The first examples of phosphine complexes of the weakly Lewis acidic silicon tetraiodide have been characterized, including the spontaneous formation of the cation [SiI3(PMe3)2][I], which contrasts with the chemistry of the lighter halides with PMe3, where only the neutral trans-octahedral [SnX4(PMe3)2] complexes were observed.14 Silicon(IV) iodide was also shown to react with the diphosphine ligands Et2P(CH2)2PEt2 and o-C6H4(PMe2)2 to form six-coordinate neutral complexes with cis-octahedral coordination, the first known soft donor complexes featuring the SiI4 unit.

There are no structurally characterized silicon tetraiodide complexes with neutral As-donor or S-donor ligands,2,11 and with NHC ligands, all structurally characterized examples are cationic due to iodide displacement.5,9,10

The discrete [SiX3(PMe3)2]+ (X = Cl, Br) cations have been synthesized by the reaction of the tetrahalide complexes with Na[BArF], while the reaction of [SiCl4(PMe3)2] with TMSOTf leads to the formation of neutral complexes [SiCl3(PMe3)2(OTf)] and [SiCl2(PMe3)2(OTf)2], in which the OTf groups remain coordinated to the silicon center. The reactions of [SiX4(PMe3)2] with AlX3 led to the removal of the phosphine from the silicon center. Such Si(IV) cations may find application for Lewis acid promoted transformations in organic chemistry.

DFT calculations suggest that the charge on the silicon center in [SiX4(PMe3)2] and [SiX3(PMe3)2]+ increases in the series F > Cl > Br > I, in line with expectations based on the decreasing electronegativity going down group 17. Upon going from the tetrahalide species to the trihalide cations, NBO analysis shows that the majority of the change in the charge occurs in the atoms of the ‘SiX3’ fragment with no significant change in the charge on the phosphorus atom.

Acknowledgments

We thank EPSRC for funding via the ADEPT Programme Grant EP/NO335437/1 and EP/PO25137/1. We also thank Dr. Mark E. Light for help with resolving the crystallographic twinning.

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.inorgchem.2c02949.

  • Crystallographic parameters for the crystal structures reported; cif files for the crystal structures described; full details of the computational work; and original IR, 1H, 19F{1H}, 29Si, and 31P{1H} NMR spectra for the reported complexes (PDF)

The authors declare no competing financial interest.

Supplementary Material

ic2c02949_si_002.pdf (2.2MB, pdf)

References

  1. a Rappoport Z.; Patai S. (Eds), The Chemistry of Organic Silicon Compounds. Wiley: New York, 1991, 2001; Vol. 1–3; [Google Scholar]; b Brook M. A.Silicon in Organic, Organometallic and Polymer Chemistry. Wiley, New York, 1999; [Google Scholar]; c Holmes R. R. Comparison of phosphorus and silicon: hypervalency, stereochemistry and reactivity. Chem. Rev. 1996, 96, 927–950. 10.1021/cr950243n. [DOI] [PubMed] [Google Scholar]
  2. Levason W.; Reid G.; Zhang W. Coordination complexes of silicon and germanium halides with neutral ligands. Coord. Chem. Rev. 2011, 255, 1319–1341. 10.1016/j.ccr.2010.11.019. [DOI] [Google Scholar]
  3. Hermannsdorfer A.; Driess M. Silicon Tetrakis(trifluoromethanesulfonate): A simple neutral silane acting as a soft and hard Lewis superacid. Angew. Chem., Int. Ed. 2021, 60, 13656–13660. 10.1002/anie.202103414. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Chuit C.; Corriu R. J. P.; Reye C.; Young J. C. Reactivity of penta- and hexacoordinate silicon compounds and their role as reaction intermediates. Chem. Rev. 1993, 93, 1371–1448. 10.1021/cr00020a003. [DOI] [Google Scholar]
  5. a Ghadwal R. S.; Roesky H. W.; Merkel S.; Henn J.; Stalke D. Lewis base stabilized dichlorosilylene. Angew. Chem., Int. Ed. 2009, 48, 5683–5686. 10.1002/anie.200901766. [DOI] [PubMed] [Google Scholar]; b Wang Y.; Xie Y.; Wei P.; King R. B.; Schaefer H. F. III; von R. Schleyer P.; Robinson G. H. A stable silicon(0) compound with a Si=Si double bond. Science 2008, 321, 1069–1071. 10.1126/science.1160768. [DOI] [PubMed] [Google Scholar]; c Filippou A. C.; Chernov O.; Schnakenburg G. Metal–silicon triple bonds: the molybdenum silylidyne complex [Cp(CO)2Mo(Si-R)]. Angew. Chem., Int. Ed. 2009, 48, 5687–5690. 10.1002/anie.200902431. [DOI] [PubMed] [Google Scholar]; d Böttcher T.; Bassil B. S.; Zhechkov L.; Heine T.; Röschenthaler G.-V. (NHCMe)SiCl4: a versatile carbene transfer reagent – synthesis from silicochloroform. Chem. Sci. 2013, 4, 77–83. 10.1039/C2SC21214E. [DOI] [Google Scholar]; e Nagendran S.; Roesky H. W. The chemistry of aluminum(I), silicon(II), and germanium(II). Organometallics 2008, 27, 457–492. 10.1021/om7007869. [DOI] [Google Scholar]; f Asay M.; Jones C.; Driess M. N-Heterocyclic carbene analogues with low-valent Group 13 and Group 14 elements: Syntheses, structures, and reactivities of a new generation of multitalented ligands. Chem. Rev. 2011, 111, 354–396. 10.1021/cr100216y. [DOI] [PubMed] [Google Scholar]
  6. Cheng F.; Hector A. L.; Levason W.; Reid G.; Webster M.; Zhang W. Preparation and structure of the unique silicon(IV) cation [SiF3(Me3tacn)]+. Chem. Commun. 2009, 1334–1336. 10.1039/b822236c. [DOI] [PubMed] [Google Scholar]
  7. Denmark S. E.; Eklov B. M. Neutral and cationic phosphoramide adducts of silicon tetrachloride: synthesis and characterisation of their solution and solid state structures. Chem. – Eur. J. 2008, 4, 234–239. [DOI] [PubMed] [Google Scholar]
  8. Everett M.; Jolleys A.; Levason W.; Light M. E.; Pugh D.; Reid G. Cationic aza-macrocyclic complexes of germanium(II) and silicon(IV). Dalton Trans. 2015, 44, 20898–20905. 10.1039/C5DT03941J. [DOI] [PubMed] [Google Scholar]
  9. a Böttcher T.; Steinhauer S.; Neumann B.; Stammler H.-G.; Röschenthaler G. V.; Hoge B. Pentacoordinate silicon(IV): cationic, anionic and neutral complexes derived from the reaction of NHC⃗SiCl4 with highly Lewis acidic (C2F5)2SiH2. Chem. Commun. 2014, 50, 6204–6206. 10.1039/C4CC02583K. [DOI] [PubMed] [Google Scholar]; b Böttcher T.; Steinhauer S.; Lewis-Alleyne L. C.; Neumann B.; Stammler H.-G.; Bassil B. S.; Röschenthaler G. V.; Hoge B. NHC -> SiCl4: An ambivalent carbene-transfer reagent. Chem. – Eur. J. 2015, 21, 893–899. 10.1002/chem.201404628. [DOI] [PubMed] [Google Scholar]
  10. Filippou A. C.; Lebedev Y. N.; Chernov O.; Straßmann M.; Schnakenburg G. Silicon(II) coordination chemistry: N-heterocyclic carbene complexes of Si2+ and SiI+. Angew. Chem., Int. Ed. 2013, 52, 6974–6978. 10.1002/anie.201301363. [DOI] [PubMed] [Google Scholar]
  11. Burt J.; Levason W.; Reid G. Coordination chemistry of the main group elements with phosphine, arsine and stibine ligands. Coord. Chem. Rev. 2014, 280, 65–125. [Google Scholar]
  12. a Blayden H.; Webster M. The crystal structure of bis(trimethylphosphine) tetrachlorosilicon(IV). Inorg. Nucl. Chem. Lett. 1970, 6, 701–705. [Google Scholar]; b Beattie I. R.; Ozin G. Vibrational spectra, vibrational analysis, and shapes of some 1 : 1 and 1 : 2 addition compounds of group IV tetrahalides with trimethylamine and trimethylphosphine. J. Chem. Soc. A 1970, 370–377. 10.1039/j19700000370. [DOI] [Google Scholar]; c Beattie I. R.; Ozin G. A. The acceptor properties of silicon(IV). ‘Class (b)’ or ‘soft acid’ behaviour by silicon tetrachloride and silicon tetrabromide. J. Chem. Soc. (A) 1969, 2267–2269. 10.1039/J19690002267. [DOI] [Google Scholar]
  13. George K.; Hector A. L.; Levason W.; Reid G.; Sanderson G.; Webster M.; Zhang W. Hypervalent neutral O-donor ligand complexes of silicon tetrafluoride, comparisons with other Group 14 tetrafluorides and a search for soft donor ligand complexes. Dalton Trans. 2011, 40, 1584–1593. 10.1039/c0dt01115k. [DOI] [PubMed] [Google Scholar]
  14. Levason W.; Pugh D.; Reid G. Phosphine and diphosphine complexes of silicon(IV) halides. Inorg. Chem. 2013, 52, 5185–5193. 10.1021/ic400077z. [DOI] [PubMed] [Google Scholar]
  15. Mantina M.; Chamberlin A. C.; Valero R.; Cramer C. J.; Truhlar D. G. Consistent Van der Waals radii for the whole main group. J. Phys. Chem. A 2009, 113, 5806–5812. 10.1021/jp8111556. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Kolonits M.; Hargittai M. Molecular structure of silicon tetraiodide. Struct. Chem. 1998, 9, 349–352. 10.1023/A:1022462926682. [DOI] [Google Scholar]
  17. a Greenacre V. K.; King R. P.; Levason W.; Reid G. Neutral and cationic phosphine and arsine complexes of tin(IV) halides: synthesis, properties, structures and anion influence. Dalton Trans. 2019, 48, 17097–17105. 10.1039/C9DT03683K. [DOI] [PubMed] [Google Scholar]; b King R. P.; Woodward M. S.; Grigg J.; McRobbie G.; Levason W.; Reid G. Tin(IV) fluoride complexes with neutral phosphine coordination and comparisons with hard N- and O-donor ligands. Dalton Trans. 2021, 50, 14400–14410. 10.1039/D1DT02948G. [DOI] [PubMed] [Google Scholar]; c King R. P.; Levason W.; Reid G. Neutral and cationic germanium(IV) fluoride complexes with phosphine coordination – synthesis, spectroscopy and structures. Dalton Trans. 2021, 50, 17751–17765. 10.1039/D1DT03339E. [DOI] [PubMed] [Google Scholar]; d Woodward M. S.; King R. P.; Bannister R. D.; Grigg J.; McRobbie G.; Levason W.; Reid G. Fluoro-germanium(IV) cations with neutral co-ligands - synthesis, properties and comparison with neutral GeF4 adducts. Inorganics 2022, 10, 107. 10.3390/inorganics10080107. [DOI] [Google Scholar]
  18. Kyba E. P.; Liu S. T.; Harris R. L. A facile synthesis of 1,2-bis(phosphino)benzene and related alkylated species. Organometallics 1983, 2, 1877–1879. 10.1021/om50006a031. [DOI] [Google Scholar]
  19. a Sheldrick G. M. Crystal structure refinement with SHELXL. Acta Crystallogr., Sect. A: Found. Crystallogr. 2015, 71, 3–8. 10.1107/S2053229614024218. [DOI] [PMC free article] [PubMed] [Google Scholar]; b 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]; c Dolomanov O. V.; Bourhis L. J.; Gildea R. J.; Howard J. A. K.; Puschmann H. OLEX2: a complete structure solution, refinement and analysis program. J. Appl. Crystallogr. 2009, 42, 339–341. 10.1107/S0021889808042726. [DOI] [Google Scholar]
  20. a Frisch M. J.; Trucks G. W.; Schlegel H. B.; Scuseria G. E.; Robb M. A.; Cheeseman J. R.; Scalmani G.; Barone V.; Petersson G. A.; Nakatsuji H.; Li X.; Caricato M.; Marenich A. V.; Bloino J.; Janesko B. G.; Gomperts R.; Mennucci B.; Hratchian H. P.; Ortiz J. V.; Izmaylov A. F.; Sonnenberg J. L.; Williams-Young D.; Ding F.; Lipparini F.; Egidi F.; Goings J.; Peng B.; Petrone A.; Henderson T.; Ranasinghe D.; Zakrzewski V. G.; Gao J.; Rega N.; Zheng G.; Liang W.; Hada M.; Ehara M.; Toyota K.; Fukuda R.; Hasegawa J.; Ishida M.; Nakajima T.; Honda Y.; Kitao O.; Nakai H.; Vreven T.; Throssell K.; Montgomery J. A. Jr.; Peralta J. E.; Ogliaro F.; Bearpark M. J.; Heyd J. J.; Brothers E. N.; Kudin K. N.; Staroverov V. N.; Keith T. A.; Kobayashi R.; Normand J.; Raghavachari K.; Rendell A. P.; Burant J. C.; Iyengar S. S.; Tomasi J.; Cossi M.; Millam J. M.; Klene M.; Adamo C.; Cammi R.; Ochterski J. W.; Martin R. L.; Morokuma K.; Farkas O.; Foresman J. B.; Fox D. J.. Gaussian 16, Revision C.01; Gaussian, Inc.: Wallingford, CT, 2016;; b Grimme S. Semiempirical GGA-type density functional constructed with a long-range dispersion correction. J. Comput. Chem. 2006, 27, 1787–1799. 10.1002/jcc.20495. [DOI] [PubMed] [Google Scholar]; c Grimme S.; Ehrlich S.; Goerigk L. Effect of the damping function in dispersion corrected density functional theory. J. Comput. Chem. 2011, 32, 1456–1465. 10.1002/jcc.21759. [DOI] [PubMed] [Google Scholar]
  21. Lee C.; Yang W.; Parr R. G. Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density. Phys. Rev. B 1988, 37, 785–789. 10.1103/PhysRevB.37.785. [DOI] [PubMed] [Google Scholar]
  22. Krishnan R.; Binkley J. S.; Seeger R.; Pople J. A. Self-consistent molecular orbital methods. XX. A basis set for correlated wave functions. J. Chem. Phys. 1980, 72, 650–654. 10.1063/1.438955. [DOI] [Google Scholar]
  23. Wadt W. R.; Hay P. J. ab initio effective core potentials for molecular calculations. Potentials for main group elements Na to Bi. J. Chem. Phys. 1985, 82, 284–298. 10.1063/1.448800. [DOI] [Google Scholar]

Associated Data

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

Supplementary Materials

ic2c02949_si_002.pdf (2.2MB, pdf)

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

RESOURCES