Skip to main content
NCBI home page
ACS AuthorChoice logoLink to ACS AuthorChoice
. 2022 May 10;61(20):7869–7877. doi: 10.1021/acs.inorgchem.2c00456

Tetrahedral M4(μ4-O) Motifs Beyond Zn: Efficient One-Pot Synthesis of Oxido–Amidate Clusters via a Transmetalation/Hydrolysis Approach

Piotr Krupiński †, Michał Terlecki ‡, Arkadiusz Kornowicz †,*, Iwona Justyniak †, Daniel Prochowicz †, Jan van Leusen §, Paul Kögerler §, Janusz Lewiński †,‡,*
PMCID: PMC9131453  PMID: 35536182

Abstract

graphic file with name ic2c00456_0008.jpg

While zinc μ4-oxido-centered complexes are widely used as versatile precursors and building units of functional materials, the synthesis of their analogues based on other transition metals is highly underdeveloped. Herein, we present the first efficient systematic approach for the synthesis of homometallic [M4(μ4-O)L6]-type clusters incorporating divalent transition-metal centers, coated by bridging monoanionic organic ligands. As a proof of concept, we prepared a series of charge-neutral metal-oxido benzamidates, [M4(μ4-O) (NHCOPh)6] (M = Fe, Co, Zn), including iron(II) and cobalt(II) clusters not accessible before. The resulting complexes were characterized using elemental analysis, FTIR spectroscopy, magnetic measurements, and single-crystal X-ray diffraction. Detailed structural analysis showed interesting self-assembly of the tetrahedral clusters into 2D honeycomb-like supramolecular layers driven by hydrogen bonds in the proximal secondary coordination sphere. Moreover, we modeled the magnetic properties of new iron (II) and cobalt (II) clusters, which display a general tendency for antiferromagnetic coupling of the μ4-O/μ-benzamidate-bridged metal centers. The developed synthetic procedure is potentially easily extensible to other M(II)-oxido systems, which will likely pave the way to new oxido clusters with interesting optoelectronic and self-assembly properties and, as a result, will allow for the development of new functional materials not achievable before.

Short abstract

While zinc μ4-oxido-centered complexes are easily accessible building units of functional materials, the synthesis of their analogues based on other transition metals is highly underdeveloped. Herein, we present the first efficient systematic approach for the synthesis of [M4(μ4-O)]-type clusters incorporating divalent transition-metal centers. As prepared, a series of model metal-oxido benzamidates revealed interesting trends in their self-assembly and magnetic properties.

Introduction

Molecular metal-oxido clusters have gained attention as versatile building units of a wide variety of functional materials based on both coordination1,2 and noncovalent supramolecular networks.3,4 The most prominent subsets of metal-oxido clusters include trinuclear μ3-oxido-centered complexes, tetranuclear μ4-oxido clusters, and multinuclear polyoxidometalates (POMs) (Figure 1a). Among them, clusters comprising a highly symmetrical tetrahedral [M4(μ4-O)]6+ core (M = divalent metal) stabilized by six monoanionic bidentate organic ligands are of particular interest due to their multifaceted chemistry arising from the presence of several spots of structural tailorability, including divalent metal centers in the tetrahedral core, the character of anchoring groups, and the organic backbone of ligands in the secondary coordination sphere (Figure 1b).5,6 Such diversity of structural features results in tuneable optoelectronic and coordination properties, which turns μ4-oxido compounds into suitable candidates for magnetic,7 luminescent,8−10 and catalytic11−15 materials. Moreover, [M4(μ4-O)L6]-type complexes can be regarded as discrete soluble intermediates between simple monomers and polymeric lattices of various hybrid organic–inorganic architectures. As such, they are widely used as model systems for studying properties of more complex systems including MOFs16,17 and hybrid metal oxide nanoparticles,18,19 as well as effective precursors of functional materials.5,6,20−26 Nevertheless, the development of materials containing the [M4(μ4-O)] structural motif beyond zinc clusters is hampered by the lack of facile access to this class of complexes comprising metal centers of desired optoelectronic, catalytic, or magnetic properties. For instance, access to homometallic isoreticular MOF-5 analogues based on metals other than zinc is still very limited. To the best of our knowledge, three Co(II) pyrazolate frameworks are the only examples of such materials obtained via direct synthesis from inorganic salts.27−29 Strikingly, this approach failed in the case of isoreticular frameworks based on dicarboxylate linkers. We also note that MOF-5(Co) and MOF-5(Be) were obtained from well-defined metal-oxido precursors using the controlled SBU approach,20 and cobalt (II) MOF-5 analogues were obtained by a post-synthetic transmetalation.17,30 However, the latter process was not effective for other metal ions.

Figure 1.

Figure 1

Open in a new tab

(a) Main families of metal-oxido compounds. (b) Multifaceted chemistry of tetrahedral μ4-oxido [M4(μ4-O)L6]-type complexes.

To date, readily accessible zinc μ4-oxido clusters have been the subject of the most extensive investigations. For example, the most common zinc-oxido carboxylates are easily prepared by either thermal decomposition of zinc carboxylates via elimination of the corresponding anhydride31 or in alkaline solutions of zinc salts with water acting as a source of the O2– ion.10,32,33 An increased control over the process of zinc-oxido carboxylates formation was achieved by using homoleptic zinc carbamates as well-defined precursors acting simultaneously as water deprotonation agents (Figure 2a).34−37 Another approach based on well-defined precursors utilizes diorganozinc species, which are reacted with the appropriate proligand, and then are exposed to dioxygen38−40 or undergo hydrolysis by addition of a stoichiometric amount of water (Figure 2b).3,5,6,16,18,19,21,41−44 In the hydrolytic transformation, the high Brønsted basicity of alkylzinc moieties is not only used to generate O2– ions but also facilitates initial deprotonation of the proligand. This approach enabled the synthesis of μ4-oxido complexes incorporating a wide range of organic ligands, namely, carboxylates,5,16,21 phosphinates,18,19,42 amidates,23 amidinates,6,26,41,43 and guanidinates.44 Despite the wide scope of applied [Zn4(μ4-O)]6+ core coating ligands, this relatively universal approach for Zn–oxido complexes is essentially non-transferable to the related transition-metal systems.

Figure 2.

Figure 2

Open in a new tab

Controlled synthesis of metal μ4-oxido [M4(μ4-O)L6]-type clusters from well-defined precursors: (a) carbamate approach, (b) organometallic approach, and (c) one-pot transmetalation/hydrolysis approach.

In contrast to zinc–oxido complexes, tetrahedral open-shell transition metal–oxido complexes were mostly obtained serendipitously, seldom by design.45 For example, Mn(II), Fe(II), and Co(II) μ4-oxido clusters stabilized by N,N′-bidentate ligands were isolated from reactions of inorganic metal salts with lithiated ligands.46−48 In all cases, contamination by atmospheric oxygen or moisture was indicated as the source of the O2– ions. Similarly, a 3,5-dimethylpyrazolate cobalt-oxido cluster was obtained unexpectedly during attempts to synthesize the mixed cobalt/zinc [Co1/3Zn2/3(Hdmpz)2]x (Hdmpz = 3,5-dimethylpyrazole) complex.49 Furthermore, to the best of our knowledge, the carbamate cluster [Co4(μ4-O) (OOCNC9H18)6], obtained via the insertion of a TEMPO radical into Co2(CO)87,50 is the only [M4(μ4-O)L6] system characterized magnetically. Therefore, we believe that the application potential of tetrahedral oxido-centered clusters as functional materials cannot be fully revealed without a reliable synthesis method applicable to metal centers of various characters.

Herein, we present a novel one-pot transmetalation/hydrolysis procedure for the synthesis of homometallic oxido clusters incorporating various divalent metal centers (Figure 2c). The efficiency of the developed approach was demonstrated by the preparation of an amide-stabilized zinc-oxido complex [Zn4(μ4-O)(NHCOPh)6] (1-Zn) and its hitherto inaccessible iron (II) and cobalt (II) analogues (1-Fe and 1-Co). The structural characterization of 1-Fe, 1-Co, and 1-Zn revealed that they all exhibit similar self-assembly properties resulting in a honeycomb-like supramolecular motif. Furthermore, magnetic characterization of 1-Fe and 1-Co shows strong antiferromagnetic interactions between the metal centers within the [M4(μ4-O)] core likely mediated by the tetrahedral O2– bridges.

Experimental Section

General Considerations

All manipulations were conducted under a dry, oxygen-free argon atmosphere either using standard Schlenk techniques or in a glovebox. All reagents were purchased from commercial vendors: benzamide (Sigma), KH (Sigma), cobalt (II) chloride (ABCR), iron (II) chloride (ABCR), zinc chloride and used as received. Solvents were purified using an MBraun SPS-5 system.

General Procedure for the Synthesis of 1-Fe, 1-Co, and 1-Zn

Equimolar amounts of benzamide (0.969 g, 8.00 mmol) and KH (0.320 g, 8 mmol) were placed in a Schlenk flask cooled to 0 °C and dispersed in THF (30 mL). After a few minutes, the reaction mixture was allowed to gradually warm to room temperature and stirred for 24 h. Then, FeCl2 (0.507 g, 4 mmol), CoCl2 (0.519 g, 4 mmol), or ZnCl2 (0.545 g, 4 mmol) was added. After another 8 h of stirring, 18 μL (1 mmol) of Millipore water and 10 mL of dimethylformamide (DMF) were added and the reaction mixture was stirred for another 24 h. The product was isolated as red-brown (1-Fe), dark blue (1-Co), or colorless (1-Zn) crystals after filtration and crystallization in the presence of hexane vapor at room temperature (yield = 71%, 755 mg (1-Fe); 79%, 859 mg (1-Co); 75%, 830 mg (1-Zn)).

Characterization

FTIR spectra were measured with a Bruker Tensor II spectrometer using the ATR technique. Elemental analyses were performed using a UNICUBE elemental analyzer (Elementar Analysensysteme GmbH). Powder XRD data were collected on a PANalytical Empyrean diffractometer with Ni-filtered Cu Kα radiation (λ = 1.5406 Å) or Bruker D8 Advance diffractometer with V-filtered Cr Kα radiation (λ = 2.2897 Å). The sample was spread on a surface of a silicon plate fixed to the sample holder and sealed by a Capton tape. Diffraction patterns were collected by scanning with a step of 0.02°.

1-Fe: IR (ATR): ν/cm–1 3347 (w), 3065 (vw), 2951 (vw), 2862 (vw), 1667 (m), 1599 (s), 1540(vs), 1508 (w), 1438 (vs), 1220 (s), 1117 (m), 1030 (w), 933 (w), 699 (vs), 668 (s), 472 (vs). Elemental analysis: calcd (%) for 1-Fe·0.84 THF·0.58 DMF (C47.1H46.8N6.6O8.4Fe4) (1063.13): C, 53.21; H, 4.44; N, 8.67. Found (%): C, 53.33; H, 4.32; N, 8.77.

1-Co: IR (ATR): ν/cm–1 3348 (w), 3068 (vw), 2973 (vw), 2863 (vw), 1674 (m), 1599 (s), 1555(vs), 1506 (w), 1454 (vs), 1388 (w), 1234 (s), 1133 (m), 1030 (w), 701 (vs), 670 (s), 489 (vs). Elemental analysis: calcd (%) for 1-Co·0.93 THF·0.59 DMF (C47.5H47.5N6.6O8.5Co4) (1082.70): C, 52.68; H, 4.43; N, 8.53. Found (%): C, 52.91; H, 4.19; N 8.72.

1-Zn: 1H NMR (300 MHz, CDCl3): δ [ppm] 7.90–7.73 (m, 12H, Ph), 7.46–7.32 (m, 18H, Ph), 6.36 (s, 1.2H, NH), 6.24 (s, 2.4H, NH), 6.15 (s, 1.2H, NH); 13C NMR (75 MHz, CDCl3): δ [ppm] 177.12 (NCO), 137.03 (IVCAr), 130.55 (CAr), 128.14 (CAr), 127.36 (CAr); IR (ATR): ν/cm–1 3361 (w), 3063 (vw), 2976 (vw), 2863 (vw), 1672 (m), 1599 (s), 1557 (s), 1501 (m), 1449 (vs), 1388 (w), 1233 (s), 1131 (m), 1028 (w), 697 (vs), 674 (s), 488 (s). Elemental analysis: calcd (%) for 1-Zn·0.68 THF·0.75 DMF (C47H47N6.75O8.43Zn4) (1102.16): C, 51.19; H, 4.27; N, 8.58. Found (%): C, 51.22; H, 4.22; N, 8.61.

X-ray Structure Determination

The data were collected at 100(2) K on a Nonius Kappa CCD diffractometer51 using graphite monochromated Mo Kα radiation (λ = 0.71073 Å). The crystal was mounted in a nylon loop in a drop of silicon oil to prevent the possibility of decay of the crystal during data collection. The unit cell parameters were determined from ten frames and then refined on all data. The data were processed with DENZO and SCALEPACK (HKL2000 package).52 The structure was solved by direct methods using the SHELXS-97 program and was refined by full matrix least-squares on F2 using the program SHELXL-97.53 All non-hydrogen atoms were refined with anisotropic displacement parameters. The hydrogen atoms were introduced at geometrically idealized coordinates with a fixed isotropic displacement parameter equal to 1.5 (methyl groups) times the value of the equivalent isotropic displacement parameter of the parent carbon. Crystallographic data (excluding structure factors) for the structure reported in this paper have been deposited with the Cambridge Crystallographic Data Centre as a supplementary publication. Copies of the data can be obtained free of charge on application to CCDC, 12 Union Road, Cambridge CB21EZ, UK (fax: (+44)1223-336-033; e-mail: deposit@ccdc.cam.ac.uk). CCDC: 2122831 (1-Fe); 2122830 (1-Co); 2122832 (1-Zn).

Magnetic Measurements

Magnetic properties were determined using a Quantum Design MPMS–5XL SQUID magnetometer for direct current (dc) and alternating current (ac) measurements. Microcrystalline samples of 1-Fe and 1-Co were compacted and immobilized into cylindrical PTFE sample holders. Experimental dc data were recorded at 0.1 T in the temperature range 2.0–290 K and at 2.0 K in the field range 0.1–5.0 T. Experimental ac data were collected at a zero static bias field in the temperature range 2.0–50 K and frequency range 3–1000 Hz using an amplitude of Bac = 3 G. However, no relevant out-of-phase signals were detected for either compound. All data were corrected for the diamagnetic contributions of the sample holders and the compound (χm,dia/10–4 cm3 mol–1 = −5.37 (1-Fe), −5.31 (1-Co)).

Results and Discussion

Synthesis of [M4(μ4-O)(NHC(O)Ph)6] (M = Fe, Co, Zn) Complexes

Metal μ4–oxido complexes were prepared using a new synthetic procedure that involves three main steps: (i) generation of a potassium salt from the selected proligand L-H, (ii) transmetalation reaction with M(II) salt, and (iii) stoichiometric hydrolysis of the received homoleptic M(II) complex (Figure 1c). Benzamide-coated clusters were selected as model systems due to their close resemblance to the SBUs of the archetypal MOFs. To demonstrate the applicability of the proposed methodology, we first performed the synthesis of the zinc–oxido complex (1-Zn). Subsequently, we prepared the Co(II)- and Fe(II)-based μ4–oxido complexes (1-Co and 1-Fe), as examples of the elusive homologues based on magnetically active and redox-active elements.

In a typical procedure, equimolar amounts of KH and benzamide were placed in a Schlenk flask and dispersed in THF. The reaction mixture was stirred overnight, and then, a 0.5 molar equivalent of MCl2 (M = Fe, Co, Zn) was added. After another 12 h, the obtained red-brown (Fe), deep blue (Co), or white (Zn) suspensions were hydrolyzed using the 1:4 H2O/M molar ratio. To increase the solubility of the resulting metal–oxido complexes, DMF was added to the reaction mixture, and the solution was stirred overnight. Then, the KCl slurry was removed by filtration, and the respective product was isolated as well-shaped red-brown (Fe), deep blue (Co), or colorless (Zn) crystals (Figure S8) by slow diffusion of hexane vapor into the parent solution (for systematic characterization of the resulting complexes vide infra).

A key aspect of the developed process is the highly efficient metathesis transmetalation driven by the low solubility of KCl in the employed organic solvent. The use of a potassium salt also allows to effectively eliminate the incorporation of alkali ions into the final product, which was reported to occur in the case of Li- or Zn-based salts used in transmetalation processes.22,39,43,54−56 Advantageously, potassium salts of highly basic ligands like amides can be easily generated in situ by the reaction of a selected proligand L-H with KH, where the only side product is H2, which finally enables a one-pot synthesis. Furthermore, the utilization of ligands with sufficiently high basicity is a crucial factor for ensuring proper reactivity of a homoleptic ML2 complex, which acts as both (i) the source of M(II) ions and stabilizing ligands, as well as (ii) the water-deprotonating agent. Overall, the transmetalation/hydrolysis process leads to the desired product [M4(μ4-O)L6] in high purity, with the generation of three easy-to-separate side products: (i) gaseous H2 leaving the reaction system, (ii) KCl precipitate that can be removed by filtration, and (iii) the starting proligand, which can be separated from the product by crystallization and reused. Due to the above-mentioned qualities, the developed methodology is potentially easily applicable to other μ4-O systems based on various M(II) metal centers and a wide range of organic ligands with high basicity such as amidinate, ureate, or guanidinate anions.

Structural Characterization

Complexes 1-Fe, 1-Co, and 1-Zn were characterized spectroscopically and by single-crystal X-ray diffraction and elemental analysis. Compound 1-Zn was previously obtained via the organometallic synthesis,23 and the current characteristics (for details, see Experimental Section and Supporting Information) are consistent with the previous results. The FTIR spectra of 1-Fe and 1-Co are analogous to 1-Zn indicating the presence of monoanionic benzamide ligands along with the [M4(μ4-O)] core characterized by the M-O bands observed at 477, 487, and 488 cm–1 for iron, cobalt, and zinc cluster, respectively (Figure S9). Analysis of the crystal structures indicates that 1-Fe, 1-Co, and 1-Zn are isostructural and crystalize in the P3̅c1 space group as solvates with THF and DMF. The elemental (see Experimental Section) and 1H NMR analysis (Figure S10) indicates the 1:THF/DMF stoichiometry as approximately 1:0.75:0.75; however, the solvent content can vary in bulk samples.

The molecular structure of the complexes 1-Fe, 1-Co, and 1-Zn comprises a tetrahedral [M4(μ4-O)] core coated by six μ2 monoanionic benzamidate ligands (Figure 3). The M–O bonds to the central O2– ion are in the range 1.973–1.974, 1.948–1.955, and 1.941–1.961 Å for 1-Fe, 1-Co, and 1-Zn, respectively. These values are in line with the M–O bond lengths observed in previously reported iron (II) (1.952–1.955 Å),46 cobalt (II) (1.928–1.956 Å),50 and zinc (II) (1.935–1.966 Å)5,6 tetrahedral oxido clusters. In turn, the M–O and M–N metal-to-amidate bond lengths (1-Fe: 1.972–2.023, 1-Co: 1.941–1.996, 1-Zn: 1.958–2.005 Å) are longer than typical M–O (Fe–O: 1.936–1.978 Å,57 Co–O: 1.929–1.950 Å,50 Zn–O: 1.922–1.962 Å5) but shorter than typical M–N (Fe–N: 2.044–2.070 Å,46 Co–N: 2.000–2.059 Å,46 Zn–N: 1.997–2.035 Å6,46) bond lengths in known oxido–metal clusters. This observation indicates a disorder in the arrangement of N and O atoms in the crystal structures of 1-Fe, 1-Co, and 1-Zn, which suggests the occurrence of the coordination position isomerism in the benzamidate anions. Specifically, each of them may act either as an (O,N)- or (N,O)-bidentate ligand, which overall gives four isomers bearing metal centers with varying coordination environments: M(NNN)M(OON)M(OON)M(OON), M(NNN)M(OOO)M(OON)M(NNO), M(NNO)M(OOO)M(NNO)M(NNO), and M(NNO)M(NOO)M(NNO)M(NOO) (Figure S5). Furthermore, each of these isomers is chiral, which adds up to four pairs of possible enantiomers occupying the same position in the crystal lattice. This coordination position isomerism introduces differences in environments around N-bonded protons, which explains the observed respective signal splitting in the 1H NMR spectrum (Figure S10, for details see Supporting Information).

Figure 3.

Figure 3

Open in a new tab

Molecular structure of the isostructural complexes 1-Fe, 1-Co, and 1-Zn; detailed information regarding the structures are provided in the Supporting Information.

Very recently, we have demonstrated that the N-bonded hydrogen atoms in the proximal secondary coordination sphere provide efficient H-donor sites for hydrogen bonds which influence the self-assembly of zinc-oxido clusters.6 In this context, we showed that complex 1-Zn, comprising both O and NH groups in the anchoring group of stabilizing ligand, self-assembles into 2D supramolecular honeycomb-like layers via pairs of complementary intermolecular NH···O hydrogen bonds (the N–H···O distance is 2.760 Å) supported by π–π interactions in the distal secondary coordination sphere (Figures 4 and S4). The new complexes 1-Fe and 1-Co exhibit similar self-assembly properties with the corresponding intermolecular O···HN distances of 2.662 and 2.783 Å, respectively (Table S10), as well as analogous packing of molecules in the crystal structure. The 2D honeycomb supramolecular layers are AA-type stacked, as a consequence forming two types of closed voids: one in the environment of two [M4(μ4-O)] cores and another one within the space limited by aromatic rings of 12 neighboring clusters (Figure 4f). These voids are filled by disordered THF or DMF solvent molecules (1.5 solvent molecules per oxido cluster). THF molecules enclosed in the voids of the former type are partially oriented due to the formation of O···HN hydrogen bonds involving the amidate NH groups.

Figure 4.

Figure 4

Open in a new tab

Crystal structure motifs of 1-Fe, 1-Co, and 1-Zn: (a,d) hexagonal assembly of oxido clusters driven by noncovalent interactions in the secondary coordination sphere; (b,e) system of intermolecular hydrogen bonds between oxido clusters; (c) schematic representation of the honeycomb-like supramolecular structure; (f) solvent accessible surfaces of the two types (blue and yellow) of closed voids between 2D supramolecular honeycomb-like layers.

Magnetic Characterization

Comprehensive characterization of physicochemical properties of molecular building blocks is crucial for designing new functional supramolecular assemblies. Notably, the exploration of regular [M4(μ4-O)L6]-type magnetic systems with uniform exchange pathways (i.e., coupling patterns) between all spin centers has been impeded by the inaccessibility of well-defined model complexes. To the best of our knowledge, the carbamate cluster [Co4(μ4-O)(OOCNC9H18)6] is the only system of this type characterized magnetically, albeit on a purely phenomenological level indicating antiferromagnetic interaction between the cobalt ions.7 However, tetranuclear Cu(II) cluster [Cu4(μ4-O)(OOCCF3)6(q)4] (q = quinoline) can be described as a farther-related analogue of such regular systems, based on pentacoordinate, trigonal bipyramidal metal centers.58 Its magnetic properties were extensively studied experimentally and theoretically indicating exceptionally ferromagnetic interactions within the [M4(μ4-O)] core. All other works on the magnetic properties of μ4-oxido-centered complexes involve more distorted systems with less uniform ligand spheres, commonly including monoatomic chalcogenide or alkoxide bridges prone to the mediation of strong antiferromagnetic interactions.59−62 Taking this into account, we performed magnetic characterization of the new complexes 1-Fe and 1-Co. The magnetic data indicates predominantly antiferromagnetic exchange interactions between four M(II) centers within the [M4(μ4-O)] core for both Co(II) and Fe(II) systems. This is reflected by the shape of the χmT versus T plot, the rather low value of χmT at 290 K, and the almost vanishing values of χmT and Mm at 2.0 K representing an effective total spin value of Stotal = 0 (Figures 5 and 6, see Supporting Information for a detailed discussion). These observations are consistent with the previous magnetic study for [Co4(μ4-O)(OOCNC9H18)6], which leads to the general conclusion that the tetrahedral oxido-bridges in [M4(μ4-O)] systems tend to mediate strong antiferromagnetic coupling. This phenomenon is often linked to the high M–O–M bond angles,63,64 which in 1-Fe and 1-Co fall in the range 106.3–112.4°. We also analyzed the magnetic properties of 1-Fe and 1-Co using an effective isotropic spin model, which here represents a reasonable approximation since tetrahedrally coordinated 3d6 and 3d7 centers are characterized by 5E and 4A2 ground terms, respectively. In contrast, due to the larger spin–orbit coupling of both centers, the ground terms are usually split, leading to temperature-dependent behavior of χmT below 30 K. However, this feature can be neglected for 1-Co as a relevant splitting of the A2 ground term requires a strong distortion from the tetrahedral ligand field, which is not the case for the molecular structure of 1-Co. For 1-Fe; however, the quintet E term is significantly split in any case. Therefore, the χmT versus T data for both compounds were simultaneously fitted at both 0.1 and 1.0 T, restricted to the temperature interval of 10–290 K and subsequently the values at lower temperatures were calculated. Based on the single-crystal X-ray structures, we model the M4 cluster as a trigonal pyramid, with the apex defined by threefold N-coordinated metal, since the distance from the central O here slightly differs from the other centers (as shown in Figure 3). Accordingly, we define the spin connectivity by two different exchange parameters: Jb, between the metal centers of the base (denoted by indices 2–4) and Jt, between a metal center of the base and the apical (top) metal center (index 1). Thus, the corresponding effective Hamiltonian is

graphic file with name ic2c00456_m001.jpg 1

Figure 5.

Figure 5

Open in a new tab

Temperature dependence of χmT at 0.1 (black) and 1.0 T (green circles) of 1-Fe; inset: molar magnetization Mm vs magnetic field B at 2.0 K; red lines represent the least-squares fit (above 10 K) to the effective spin model described in the text.

Figure 6.

Figure 6

Open in a new tab

Temperature dependence of χmT at 0.1 (black) and 1.0 T (green circles) of 1-Co; inset: molar magnetization Mm vs magnetic field B at 2.0 K; red lines represent the least-squares fit to the effective spin model described in the text.

The data of 1-Fe indicate a small level of paramagnetic impurities, which was accounted for in the analysis of the data. For 1-Co, we neglected such contributions, since the measurements point to a negligible level, that is, within the error margin of the fitting model. For 1-Fe, consisting of effective S = 2 centers, the least-squares fit yields Jt = (−18.6 ± 0.1) cm–1, Jb = (−15.7 ± 0.2) cm–1, and geff = 2.21 ± 0.02, and a paramagnetic impurity level corresponding to 0.0964 FeII centers per formula unit. For 1-Co (effective S = 3/2 centers), we find Jt = (−24.5 ± 0.1) cm–1, Jb = (−19.6 ± 0.1) cm–1, and geff = 2.56 ± 0.02. In both cases, the exchange interactions are antiferromagnetic, and the ground state of the respective compound can be characterized by an effective total spin Stotal of 0. For each 1-Fe and 1-Co, the obtained two J values correspond to the geometric differences, in particular the M–(μ4-O)–M angles. Furthermore, the J values for the FeII and CoII systems are very comparable when considering the different spin quantum numbers that enter the effective spin Hamiltonian as S2. The effective g factors are fully in line with tetrahedrally coordinated FeII and CoII centers.

Conclusions

We have developed a new efficient one-pot synthetic approach for tetrahedral μ4–oxido complexes of various divalent metal centers stabilized by monoanionic bridging O,N-ligands. The new synthetic procedure relies on simple stoichiometric hydrolysis of the homoleptic [ML2] complex generated in situ in a transmetalation reaction. To prove the usefulness of the developed approach, we have synthesized and characterized a series of M(II) (M = Fe, Co, Zn) oxido benzamidates. All complexes exhibit analogous honeycomb-like supramolecular structures in their crystal lattices, which indicates that their self-assembly properties are dominated by cooperative noncovalent interactions in the secondary coordination sphere and likely unaffected by the specific character of the metal center. Moreover, we have characterized the magnetic properties of the new Fe(II) and Co(II) complexes, utilizing effective spin models that underscore a general tendency for antiferromagnetic coupling of μ4-bridged metal centers in [M4(μ4-O)]-type systems.

The reported procedure is potentially easily extensible to other M(II)–oxido systems stabilized by a vast array of organic ligands. These findings will likely pave the way to new oxido clusters with interesting optoelectronic and novel molecular building units and, as a result, will allow for the development of new, as of yet elusive functional materials.

Acknowledgments

The authors acknowledge the National Science Centre Poland PRELUDIUM 10 (no. 2015/19/N/ST5/02263) and OPUS 21 (no. 2021/41/B/ST4/04414).

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.inorgchem.2c00456.

  • SC-XRD data, additional description of molecular structures and magnetic properties, PXRD patterns, and FTIR and NMR spectra (PDF)

Accession Codes

CCDC 2122830–2122832 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing data_request@ccdc.cam.ac.uk, or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

Author Contributions

∥ P.K. and M.T. contributed equally.

The authors declare no competing financial interest.

Supplementary Material

ic2c00456_si_001.pdf (1.4MB, pdf)

References

  1. Tranchemontagne D. J.; Mendoza-Cortés J. L.; O’Keeffe M.; Yaghi O. M. Secondary Building Units, Nets and Bonding in the Chemistry of Metal–Organic Frameworks. Chem. Soc. Rev. 2009, 38, 1257–1283. 10.1039/b817735j. [DOI] [PubMed] [Google Scholar]
  2. Liu J.-X.; Zhang X.-B.; Li Y.-L.; Huang S.-L.; Yang G.-Y. Polyoxometalate Functionalized Architectures. Coord. Chem. Rev. 2020, 414, 213260. 10.1016/j.ccr.2020.213260. [DOI] [Google Scholar]
  3. Prochowicz D.; Sokołowski K.; Lewiński J. Zinc Hydroxides and Oxides Supported by Organic Ligands: Synthesis and Structural Diversity. Coord. Chem. Rev. 2014, 270–271, 112–126. 10.1016/j.ccr.2013.12.003. [DOI] [Google Scholar]
  4. Stuckart M.; Monakhov K. Y. Polyoxometalates as Components of Supramolecular Assemblies. Chem. Sci. 2019, 10, 4364–4376. 10.1039/c9sc00979e. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Bury W.; Justyniak I.; Prochowicz D.; Rola-Noworyta A.; Lewiński J. Oxozinc Carboxylate Complexes: A New Synthetic Approach and the Carboxylate Ligand Effect on the Noncovalent-Interactions-Driven Self-Assembly. Inorg. Chem. 2012, 51, 7410–7414. 10.1021/ic300864n. [DOI] [PubMed] [Google Scholar]
  6. Terlecki M.; Justyniak I.; Leszczyński M. K.; Lewiński J. Effect of the Proximal Secondary Sphere on the Self-Assembly of Tetrahedral Zinc-Oxo Clusters. Commun. Chem. 2021, 4, 133. 10.1038/s42004-021-00574-3. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Jaitner P.; Veciana J.; Sporer C.; Kopacka H.; Wurst K.; Ruiz-Molina D. Synthesis, Crystal Structure, and Spectroscopic and Magnetic Properties of a New [Co4O(OOCNC9H18)6] Cluster. Organometallics 2001, 20, 568–571. 10.1021/om0003335. [DOI] [Google Scholar]
  8. Lee C.-F.; Chin K.-F.; Peng S.-M.; Che C.-M. A Luminescent Tetrameric Zinc(II) Complex Containing the 7-Azaindolate Ligand. Photophysical Properties and Crystal Structure. J. Chem. Soc., Dalton Trans. 1993, 467–470. 10.1039/DT9930000467. [DOI] [Google Scholar]
  9. Zheng S.-L.; Chen X.-M. Recent Advances in Luminescent Monomeric, Multinuclear, and Polymeric Zn(II) and Cd(II) Coordination Complexes. Aust. J. Chem. 2004, 57, 703–712. 10.1071/CH04008. [DOI] [Google Scholar]
  10. Cheng G.; So G. K.-M.; To W.-P.; Chen Y.; Kwok C.-C.; Ma C.; Guan X.; Chang X.; Kwok W.-M.; Che C.-M. Luminescent Zinc(Ii) and Copper(i) Complexes for High-Performance Solution-Processed Monochromic and White Organic Light-Emitting Devices. Chem. Sci. 2015, 6, 4623–4635. 10.1039/c4sc03161j. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Ohshima T.; Iwasaki T.; Mashima K. Direct Conversion of Esters, Lactones, and Carboxylic Acids to Oxazolines Catalyzed by a Tetranuclear Zinc Cluster. Chem. Commun. 2006, 2711. 10.1039/b605066b. [DOI] [PubMed] [Google Scholar]
  12. Maegawa Y.; Ohshima T.; Hayashi Y.; Agura K.; Iwasaki T.; Mashima K. Additive Effect of N-Heteroaromatics on Transesterification Catalyzed by Tetranuclear Zinc Cluster. ACS Catal. 2011, 1, 1178–1182. 10.1021/cs200224b. [DOI] [Google Scholar]
  13. Hayashi Y.; Ohshima T.; Fujii Y.; Matsushima Y.; Mashima K. A Trifluoroacetic Acid Adduct of a Trifluoroacetate-Bridged μ4-Oxo-Tetranuclear Zinc Cluster, Zn4(OCOCF3)6O·CF3CO2H: Synthesis under Mild Conditions and Catalytic Transesterification and Oxazoline Formation. Catal. Sci. Technol. 2011, 1, 230–233. 10.1039/c0cy00048e. [DOI] [Google Scholar]
  14. Nakatake D.; Yokote Y.; Matsushima Y.; Yazaki R.; Ohshima T. A Highly Stable but Highly Reactive Zinc Catalyst for Transesterification Supported by a Bis(Imidazole) Ligand. Green Chem. 2016, 18, 1524–1530. 10.1039/c5gc02056e. [DOI] [Google Scholar]
  15. Agura K.; Hayashi Y.; Wada M.; Nakatake D.; Mashima K.; Ohshima T. Studies of the Electronic Effects of Zinc Cluster Catalysts and Their Application to the Transesterification of β-Keto Esters. Chem.—Asian J. 2016, 11, 1548–1554. 10.1002/asia.201600062. [DOI] [PubMed] [Google Scholar]
  16. Bury W.; Justyniak I.; Prochowicz D.; Wróbel Z.; Lewiński J. Oxozinc Carboxylates: A Predesigned Platform for Modelling Prototypical Zn-MOFs’ Reactivity toward Water and Donor Solvents. Chem. Commun. 2012, 48, 7362–7364. 10.1039/c2cc33094f. [DOI] [PubMed] [Google Scholar]
  17. Brozek C. K.; Michaelis V. K.; Ong T.-C.; Bellarosa L.; López N.; Griffin R. G.; Dincă M. Dynamic DMF Binding in MOF-5 Enables the Formation of Metastable Cobalt-Substituted MOF-5 Analogues. ACS Cent. Sci. 2015, 1, 252–260. 10.1021/acscentsci.5b00247. [DOI] [PMC free article] [PubMed] [Google Scholar]
  18. Pike S. D.; White E. R.; Shaffer M. S. P.; Williams C. K. Simple Phosphinate Ligands Access Zinc Clusters Identified in the Synthesis of Zinc Oxide Nanoparticles. Nat. Commun. 2016, 7, 13008. 10.1038/ncomms13008. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Wolska-Pietkiewicz M.; Grala A.; Justyniak I.; Hryciuk D.; Jędrzejewska M.; Grzonka J.; Kurzydłowski K. J.; Lewiński J. From Well-Defined Alkylzinc Phosphinates to Quantum-Sized ZnO Nanocrystals. Chem.—Eur. J. 2017, 23, 11856–11865. 10.1002/chem.201701823. [DOI] [PubMed] [Google Scholar]
  20. Hausdorf S.; Baitalow F.; Böhle T.; Rafaja D.; Mertens F. O. R. L. Main-Group and Transition-Element IRMOF Homologues. J. Am. Chem. Soc. 2010, 132, 10978–10981. 10.1021/ja1028777. [DOI] [PubMed] [Google Scholar]
  21. Redshaw C.; Jana S.; Shang C.; Elsegood M. R. J.; Lu X.; Guo Z. X. Multinuclear Zinc Pentafluorobenzene Carboxylates: Synthesis, Characterization, and Hydrogen Storage Capability. Organometallics 2010, 29, 6129–6132. 10.1021/om100703c. [DOI] [Google Scholar]
  22. Domide D.; Walter O.; Behrens S.; Kaifer E.; Himmel H. J. Synthesis of Heterobimetallic Zn/Co Carbamates: Single-Source Precursors of Nanosized Magnetic Oxides Under Mild Conditions. Eur. J. Inorg. Chem. 2011, 860–867. 10.1002/ejic.201001095. [DOI] [Google Scholar]
  23. Prochowicz D.; Sokołowski K.; Justyniak I.; Kornowicz A.; Fairen-Jimenez D.; Friščić T.; Lewiński J. A Mechanochemical Strategy for IRMOF Assembly Based on Pre-Designed Oxo-Zinc Precursors. Chem. Commun. 2015, 51, 4032–4035. 10.1039/C4CC09917F. [DOI] [PubMed] [Google Scholar]
  24. Krupiński P.; Kornowicz A.; Sokołowski K.; Cieślak A. M.; Lewiński J. Applying Mechanochemistry for Bottom-Up Synthesis and Host-Guest Surface Modification of Semiconducting Nanocrystals: A Case of Water-Soluble β-Cyclodextrin-Coated Zinc Oxide. Chem.—Eur. J. 2016, 22, 7817–7823. 10.1002/chem.201600182. [DOI] [PubMed] [Google Scholar]
  25. Prochowicz D.; Nawrocki J.; Terlecki M.; Marynowski W.; Lewiński J. Facile Mechanosynthesis of the Archetypal Zn-Based Metal–Organic Frameworks. Inorg. Chem. 2018, 57, 13437–13442. 10.1021/acs.inorgchem.8b02026. [DOI] [PubMed] [Google Scholar]
  26. Bury W.; Walczak A. M.; Leszczyński M. K.; Navarro J. A. R. Rational Design of Noncovalent Diamondoid Microporous Materials for Low-Energy Separation of C6-Hydrocarbons. J. Am. Chem. Soc. 2018, 140, 15031–15037. 10.1021/jacs.8b09522. [DOI] [PubMed] [Google Scholar]
  27. Tonigold M.; Lu Y.; Bredenkötter B.; Rieger B.; Bahnmüller S.; Hitzbleck J.; Langstein G.; Volkmer D. Heterogeneous Catalytic Oxidation by MFU-1: A Cobalt(II)-Containing Metal-Organic Framework. Angew. Chem., Int. Ed. 2009, 48, 7546–7550. 10.1002/anie.200901241. [DOI] [PubMed] [Google Scholar]
  28. Tonigold M.; Lu Y.; Mavrandonakis A.; Puls A.; Staudt R.; Möllmer J.; Sauer J.; Volkmer D. Pyrazolate-Based Cobalt(II)-Containing Metal-Organic Frameworks in Heterogeneous Catalytic Oxidation Reactions: Elucidating the Role of Entatic States for Biomimetic Oxidation Processes. Chem.—Eur. J. 2011, 17, 8671–8695. 10.1002/chem.201003173. [DOI] [PubMed] [Google Scholar]
  29. Heering C.; Boldog I.; Vasylyeva V.; Sanchiz J.; Janiak C. Bifunctional Pyrazolate-Carboxylate Ligands for Isoreticular Cobalt and Zinc MOF-5 Analogs with Magnetic Analysis of the {Co4(μ4-O)} Node. CrystEngComm 2013, 15, 9757–9768. 10.1039/c3ce41426d. [DOI] [Google Scholar]
  30. Canossa S.; Fornasari L.; Demitri N.; Mattarozzi M.; Choquesillo-Lazarte D.; Pelagatti P.; Bacchi A. MOF Transmetalation beyond Cation Substitution: Defective Distortion of IRMOF-9 in the Spotlight. CrystEngComm 2019, 21, 827–834. 10.1039/c8ce01808a. [DOI] [Google Scholar]
  31. Hiltunen L.; Leskelä M.; Mäkelä M.; Niinistö L.; Niinistö L. Crystal Structure of μ4-Oxo-Hexakis(μ-Acetato)Tetrazinc and Thermal Studies of Its Precursor, Zinc Acetate Dihydrate. Acta Chem. Scand. 1987, 41a, 548–555. 10.3891/acta.chem.scand.41a-0548. [DOI] [Google Scholar]
  32. Hou H.; Li L.; Li G.; Fan Y.; Zhu Y. Self-Assembly of a Series of Novel Metal-Organic Compounds Containing Ferrocenecarboxylate Components. Inorg. Chem. 2003, 42, 3501–3508. 10.1021/ic034031h. [DOI] [PubMed] [Google Scholar]
  33. Karmakar A.; Baruah J. B. Synthesis and Characterization of Zinc Benzoate Complexes through Combined Solid and Solution Phase Reactions. Polyhedron 2008, 27, 3409–3416. 10.1016/j.poly.2008.07.036. [DOI] [Google Scholar]
  34. McCowan C. S.; Groy T. L.; Caudle M. T. Synthesis, Structure, and Preparative Transamination of Tetrazinc Carbamato Complexes Having the Basic Zinc Carboxylate Structure. Inorg. Chem. 2002, 41, 1120–1127. 10.1021/ic010885v. [DOI] [PubMed] [Google Scholar]
  35. Malik M. A.; O’Brien P.; Motevalli M.; Abrahams I. The Adoption of the Beryllium Acetate Structural Motif in Zinc Oxycarbamates, Oxythiocarbamates and Oxythiophosphinates. Polyhedron 2006, 25, 241–250. 10.1016/j.poly.2005.06.033. [DOI] [Google Scholar]
  36. Haywood P. F.; Hill M. R.; Roberts N. K.; Craig D. C.; Russell J. J.; Lamb R. N. Synthesis and Isomerisation Reactions of Tetranuclear and Octanuclear (Carbamato)Zinc Complexes. Eur. J. Inorg. Chem. 2008, 2024–2032. 10.1002/ejic.200700736. [DOI] [Google Scholar]
  37. Domide D.; Kaifer E.; Mautz J.; Walter O.; Behrens S.; Himmel H. J. Synthesis and Characterisation of Some New Zinc Carbamate Complexes Formed by CO2 Fixation and Their Use as Precursors for ZnO Particles under Mild Conditions. Eur. J. Inorg. Chem. 2008, 3177–3185. 10.1002/ejic.200701308. [DOI] [Google Scholar]
  38. Lewiński J.; Suwała K.; Kaczorowski T.; Gałęzowski M.; Gryko D. T.; Justyniak I.; Lipkowski J. Oxygenation of Alkylzinc Complexes with Pyrrolylketiminate Ligand: Access to Alkylperoxide versus Oxo-Encapsulated Complexes. Chem. Commun. 2009, 215–217. 10.1039/b813315h. [DOI] [PubMed] [Google Scholar]
  39. Davies R. P.; Linton D. J.; Schooler P.; Snaith R.; Wheatley A. E. H. Oxygen Capture by Lithiated Organozinc Reagents Containing Aromatic 2-Pyridylamide Ligands. Chem.—Eur. J. 2001, 7, 3696–3704. . [DOI] [PubMed] [Google Scholar]
  40. Lewiński J.; Bury W.; Dutkiewicz M.; Maurin M.; Justyniak I.; Lipkowski J. Alkylzinc Carboxylates as Efficient Precursors for Zinc Oxocarboxylates and Sulfidocarboxylates. Angew. Chem., Int. Ed. 2008, 47, 573–576. 10.1002/anie.200703125. [DOI] [PubMed] [Google Scholar]
  41. Terlecki M.; Sobczak S.; Leszczyński M. K.; Katrusiak A.; Lewiński J. Stepwise Stress-Induced Transformations of Metal-Organic Polyhedral Cluster-Based Assemblies: Where Conformational and Supramolecular Features Meet. Chem.—Eur. J. 2021, 27, 13757–13764. 10.1002/chem.202101732. [DOI] [PubMed] [Google Scholar]
  42. Lugmair C. G.; Tilley T. D.; Rheingold A. L. Zinc Di(Tert-Butyl)Phosphate Complexes as Precursors to Zinc Phosphates. Manipulation of Zincophosphate Structures. Chem. Mater. 1997, 9, 339–348. 10.1021/cm9603821. [DOI] [Google Scholar]
  43. Cole M. L.; Evans D. J.; Junk P. C.; Louis L. M. Structural and Synthetic Studies of Magnesium and Zinc Tolylformamidinate Complexes. New J. Chem. 2002, 26, 1015–1024. 10.1039/b204304a. [DOI] [Google Scholar]
  44. Neuhäuser C.; Reinmuth M.; Kaifer E.; Himmel H. J. Synthesis of Oligomeric Zinc Complexes with Bicyclic and Acyclic Guanidinate Ligands. Eur. J. Inorg. Chem. 2012, 1250–1260. 10.1002/ejic.201101223. [DOI] [Google Scholar]
  45. Haiduc I. Inverse Coordination – An Emerging New Chemical Concept. Oxygen and Other Chalcogens as Coordination Centers. Coord. Chem. Rev. 2017, 338, 1–26. 10.1016/j.ccr.2017.02.016. [DOI] [Google Scholar]
  46. Cotton F. A.; Daniels L. M.; Falvello L. R.; Matonic J. H.; Murillo C. A.; Wang X.; Zhou H. Transition Metal (Mn, Co) and Zinc Formamidinate Compounds Having the Basic Beryllium Acetate Structure, and Unique Isomeric Iron Compounds. Inorg. Chim. Acta 1997, 266, 91–102. 10.1016/S0020-1693(97)05538-2. [DOI] [Google Scholar]
  47. Cotton F. A.; Daniels L. M.; Jordan G. T.; Murillo C. A.; Pascual I. Structural Variations in the Ligands around a Simple Oxo-Centered Building Block, the Tetrahedral [M4O]6+ Unit, M=Mn and Fe. Inorg. Chim. Acta 2000, 297, 6–10. 10.1016/S0020-1693(99)00252-2. [DOI] [Google Scholar]
  48. Stokes F. A.; Kloo L.; Harford P. J.; Peel A. J.; Less R. J.; Wheatley A. E. H.; Wright D. S. Towards the Synthesis of Guanidinate- and Amidinate-Bridged Dimers of Mn and Ni. Aust. J. Chem. 2014, 67, 1081–1087. 10.1071/CH14271. [DOI] [Google Scholar]
  49. Ehlert M. K.; Rettig S. J.; Storr A.; Thompson R. C.; Trotter J. μ4-Oxo-Hexakis(μ-3,5-Dimethylpyrazolato-N,N’)Tetracobalt(II). Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 1994, 50, 1023–1026. 10.1107/S010827019301337X. [DOI] [Google Scholar]
  50. Jaitner P.; Rieker C.; Wurst K. Aggregation of Carbamato Ligands around the [Co4O]6+ Core. Synthesis and Structure of the Cluster [Co4O(O2CNC9H18)6] Prepared by a Novel Oxo-Transfer Reaction of the Nitroxyl Free Radical 2,2,6,6-Tetramethylpiperidin-1-Oxyl with [Co2(CO)8]. Chem. Commun. 1997, 1245–1246. 10.1039/a701238a. [DOI] [Google Scholar]
  51. Nonius B. V.KappaCCD Software: Delft, The Netherlands, 1998.
  52. Otwinowski Z.; Minor W. [20] Processing of X-Ray Diffraction Data Collected in Oscillation Mode. Methods Enzymol. 1997, 276, 307–326. 10.1016/s0076-6879(97)76066-x. [DOI] [PubMed] [Google Scholar]
  53. 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]
  54. Davies R. P.; Linton D. J.; Snaith R.; Wheatley A. E. H. Selective Oxygen Capture in Lithium Zincate Chemistry: The Syntheses and Solid-State Structures of (μ-O)Zn4[N(2-C5H4N)Bz]6 and But(μ3-O)Li3(μ6-O)Zn3[N(2-C5H4N)Me]6 (Bz = Benzyl). Chem. Commun. 2000, 1819–1820. 10.1039/b005238h. [DOI] [Google Scholar]
  55. Nesterov D. S.; Kokozay V. N.; Jezierska J.; Pavlyuk O. V.; Boča R.; Pombeiro A. J. L. Heterometallic Cu/Co and Cu/Co/Zn Complexes Bearing Rare Asymmetric Tetranuclear Cores: Synthesis, Structures, and Magnetic and Catalytic Properties toward the Peroxidative Oxidation of Cycloalkanes. Inorg. Chem. 2011, 50, 4401–4411. 10.1021/ic102543m. [DOI] [PubMed] [Google Scholar]
  56. Nawrocki J.; Prochowicz D.; Justyniak I.; van Leusen J.; Kornowicz A.; Kögerler P.; Lewiński J. Synthesis, Structure and Magnetic Properties of a Novel High-Nuclearity Oxo-Carboxylate [ZnxCo13–x(μ4-O)4(O2CPh)18] Cluster. Dalton Trans. 2019, 48, 12828–12831. 10.1039/C9DT02791B. [DOI] [PubMed] [Google Scholar]
  57. As iron-oxo complexes stabilized by O,O-bidentate ligands are still elusive, the values are given for dimeric carboxylates [Fe(κ2-OOCAr)(μ2-OOCAr)]2 (Ar = Mes, Xyl) featuring carboxylate ligands bridging Fe(II) centres with tetrahedral coordination geometry:Sharpe H. R.; Geer A. M.; Taylor L. J.; Gridley B. M.; Blundell T. J.; Blake A. J.; Davies E. S.; Lewis W.; McMaster J.; Robinson D.; Kays D. L. Selective Reduction and Homologation of Carbon Monoxide by Organometallic Iron Complexes. Nat. Commun. 2018, 9, 3757. 10.1038/s41467-018-06242-w. [DOI] [PMC free article] [PubMed] [Google Scholar]
  58. Ozarowski A.; Szymańska I. B.; Muzioł T.; Jezierska J. High-Field EPR and Magnetic Susceptibility Studies on Binuclear and Tetranuclear Copper Trifluoroacetate Complexes. X-Ray Structure Determination of Three Tetranuclear Quinoline Adducts of Copper(II) Trifluoroacetate. J. Am. Chem. Soc. 2009, 131, 10279–10292. 10.1021/ja902695y. [DOI] [PubMed] [Google Scholar]
  59. Bera M.; Wong W. T.; Aromi G.; Ribas J.; Ray D. A Novel Μ4-Oxo Bridged Copper Tetrahedron Derived by Self-Assembly: First Example of Double Helical Bis(Tridentate) Coordination of a Hexadentate Amine Phenol Ligand. Inorg. Chem. 2004, 43, 4787–4789. 10.1021/ic049817+. [DOI] [PubMed] [Google Scholar]
  60. Sarkar M.; Clérac R.; Mathonière C.; Hearns N. G. R.; Bertolasi V.; Ray D. New Phenoxido-Bridged Quasi-Tetrahedral and Rhomboidal [Cu4] Compounds Bearing μ4-Oxido or μ1,1-Azido Ligands: Synthesis, Chemical Reactivity, and Magnetic Studies. Inorg. Chem. 2011, 50, 3922–3933. 10.1021/ic102226j. [DOI] [PubMed] [Google Scholar]
  61. Jana M. S.; Dey S.; Priego J. L.; Jiménez-Aparicio R.; Kumar Mondal T.; Roy P. Synthesis, Characterization and Magnetic Properties of an Oxido-Bridged Tetranuclear Copper(II) Complex. Polyhedron 2013, 59, 101–106. 10.1016/j.poly.2013.04.042. [DOI] [Google Scholar]
  62. Pait M.; Shatruk M.; Lengyel J.; Gómez-Coca S.; Bauzá A.; Frontera A.; Bertolasi V.; Ray D. Two Types of Nitrito Support for Μ4-Oxido-Bridged [Cu4] Complexes: Synthesis, Crystal Structures, Magnetic Properties and DFT Analysis. Dalton Trans. 2015, 44, 6107–6117. 10.1039/c4dt03224a. [DOI] [PubMed] [Google Scholar]
  63. Melník M. Study of the Relation between the Structural Data and Magnetic Interaction in Oxo-Bridged Binuclear Copper(II) Compounds. Coord. Chem. Rev. 1982, 42, 259–293. 10.1016/S0010-8545(00)80537-8. [DOI] [Google Scholar]
  64. Chen Z.; Xu Z.; Zhang L.; Yan F.; Lin Z. Magnetic Exchange Interactions in Oxo-Bridged Diiron(III) Systems: Density Functional Calculations Coupling the Broken Symmetry Approach. J. Phys. Chem. A 2001, 105, 9710–9716. 10.1021/jp010864m. [DOI] [Google Scholar]

Associated Data

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

Supplementary Materials

ic2c00456_si_001.pdf (1.4MB, pdf)

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

RESOURCES