Article pubs.acs.org/IC
{[Si(SiMe3)3]2Ge9‑SiMe2‑(C6H4)‑SiMe2‑Ge9[Si(SiMe3)3]2K}−: The Connection of Metalloid Clusters via an Organic Linker Oleksandr Kysliak, Claudio Schrenk, and Andreas Schnepf* Chemistry Department, University Tübingen, Auf der Morgenstelle 18, D-72076 Tübingen, Germany S Supporting Information *
ABSTRACT: The reaction of [(Hyp)2Ge9]2− (Hyp = Si(SiMe3)3) with ClSiMe2-C6H4-SiMe2Cl gives [K(THF)][(Hyp)2Ge9-SiMe2-C6H4-SiMe2-Ge9(Hyp)2K] K1 in 45% yield in the form of orange-red crystals. 1 is thereby the first compound where two Ge9(Hyp)2 clusters are bound together via a bridging ligand. 1 is stable in solution but cannot be transferred intact into the gas phase via electrospray ionization indicating a higher reactivity with respect to other metalloid Ge9R3 clusters. The arrangement of the nine germanium atoms within the two Ge9 units in 1 is unique for metalloid Ge9R3 clusters. Quantum chemical calculations further reveal an electronic interaction of the two Ge9 units in 1 via the bridging phenylene group.
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INTRODUCTION
RESULTS AND DISCUSSION We recently could show that the reaction of the Zintl ion Ge94− with Hyp-Cl (Hyp = Si(SiMe3)3)8 can lead to the dianionic compound [Ge9(Hyp)2]2− when the right solvent and stoichiometry are applied.9 To this compound another silyl ligand like HypPh = Si(SiMe3)2(SiPh3) can be added, to give the first mixed substituted metalloid Ge9R3 clusters. This metathesis reaction is also possible for other ligand precursors bearing a halide atom like Cp(CO)2FeBr (Scheme 1).9,10
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On the one hand, metalloid cluster compounds of the general formula MnRm (n > m; M = metal like Al, Au, Sn, Ge, etc.; R = ligand like Si(SiMe3)3 or N(SiMe3)2) are from a fundamental point of view ideal model compounds for molecular entities in the gray area between molecules and the solid state.2 On the other hand such metalloid clusters are electronically and optically interesting building blocks for larger aggregates.2d,3,4 Thereby actually mainly self-assembly is used to obtain larger aggregates with novel physical properties.5 Recently it was shown that metalloid clusters might be covalently linked by appropriate linkers, by Petterson, Häkkinen, and Lehtovaara et al., who described the formation of dimers and trimers of the metalloid gold cluster Au102(p-MBA)44 (p-MBA = paramercaptobenzoic-acid) via dithiol linkers.6 The structure of the dimer was thereby analyzed via transmission electron microscopy (TEM) and quantum chemical calculations. Fässler et al. also described the linking of deltahedral RGe9 clusters (R = (2Z,4E)-7-amino-5-aza-hepta-2,4-dien-2-yl) via the conjugated organic building block butadiene.7 Thereby quantum chemical calculations indicate that an intramolecular cluster-tocluster electron transfer process is conceivable, as the highest occupied molecular orbital (HOMO) shows a typical electronic structure of a conjugated π-system extending over the whole molecule. However, the dimer is highly charged and thus only soluble in polar solvents like acetonitrile or dimethylformamide. Here we describe the first compound where two [Ge9(Hyp)2] units are linked via a bridging ligand, being well-soluble in tetrahydrofuran (THF). © 2017 American Chemical Society
Scheme 1. Synthesis of Mixed Substituted Metalloid Ge9(Hyp)2R− Clusters (R = HypPh; FeCp(CO)2)
Consequently, we wondered if this reaction might be used to attach more than one Ge9(Hyp)2 unit to a linker exhibiting more than one halide atom, and in the following we present a first result in this respect. The reaction of [Ge9(Hyp)2]2− with ClSiMe2-C6H4-SiMe2Cl, where two SiMe2Cl groups are bound in para position to a central phenylene group, leads to a dark red reaction solution, Received: May 12, 2017 Published: August 1, 2017 9693
DOI: 10.1021/acs.inorgchem.7b01186 Inorg. Chem. 2017, 56, 9693−9697
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Inorganic Chemistry showing a simple proton NMR spectrum. This result hints to a selective reaction, and after workup procedures we were able to isolate a product of the reaction in the form of orange-red crystals in 45% yield. X-ray crystal structure analysis of these crystals reveals that indeed the compound [K(THF)][(Hyp)2Ge9-SiMe2-C6H4-SiMe2-Ge9(Hyp)2K] K1 has formed, where within the anion 1 two Ge9(Hyp)2 clusters are linked via the bridging unit Me2Si-C6H4-SiMe2. Additionally, a potassium cation is trapped between the two Ge9(Hyp)2 units, further coordinated by the bridging phenylene ring with K−C distances in the range of 320−330 pm (Figure 1). The K−C
Table 1. Comparison of the Prism Heights [pm] in the Cluster Cores of [Ge9(Hyp)3]− (in [Li(THF)4][Ge9(Hyp)3]· 3THF),20 [Ge9(Hyp)2]2− (in [K-2,2,2-crypt]2[Ge9(Hyp)2]· 3THF)9 and the Two Cores of [(Hyp)2Ge9-SiMe2-C6H4SiMe2-Ge9(Hyp)2K]− 1 within K1
(Figure S12, Supporting Information). The Ge−K distances are again similar to those found in [(Tol)3K][Ge9(Hyp)3]. In solution the zigzag chains are completely destroyed leading to separated potassium cations and anions of 1, as dynamic light scattering (DLS)21 indicates the presence of particles in solution with a size of 3.1 ± 0.4 nm (Figure S6 Supporting Information), which fits well to 1 together with a solvent shell as the maximum dimension of 1 amounts to 2.34 nm. Hence the DLS measurements directly show that no larger aggregates are present in solution. Additionally, proton NMR measurements show only one set of signals for 1. Thereby only one signal for the hyp ligands at 0.27 ppm is observed, showing that 1 is dynamic in solution. However, despite the weak coordination of the potassium atom K2 in the zigzag chains in the solid state, the potassium atom in the anion [(Hyp) 2 Ge 9 -SiMe 2 -C 6 H 4 -SiMe 2 Ge9(Hyp)2K]− 1 (K1 in Figure 1) might be strongly bound to the cluster, as it is often the case for multiple charged clusters.22 To check if the potassium cation in 1 is still bound to the Ge18 cluster in solution we first of all tried to transfer 1 intact into the gas phase via the mild electrospray ionization technique23 that normally works well for metalloid germanium clusters of the composition [Ge9R3]−.24 However, in case of 1 very complicated mass spectra are obtained, indicating the presence of germanium clusters with 9, 18, and even 27 germanium atoms (see Supporting Information Figures S7− S9), showing that 1 is more sensitive than [Ge9(Hyp)3]−. The higher sensitivity is also obvious by first subsequent reactions of 1; for example, the reaction with ZnCl2 leads to a degradation in solution, which is indicated by a complex proton NMR spectrum of the reaction mixture. Also the addition of 2.2.2.crypt to a THF solution of K1 leads to a degradation (Figure S4, Supporting Information); that is, the bonding of the potassium cation to the dianionic cluster [(Hyp)2Ge9-SiMe2C6H4-SiMe2-Ge9(Hyp)2]2− 2 appears to be important to obtain a stable compound in solution. The instability of multicharged metalloid germanium clusters in solution seems to be a general behavior, as the metalloid cluster [Li(THF)2]3Ge14(Hyp)5 also degrades in solution after eliminating the stabilizing [Li(THF)2]+ groups by a chelating ligand.22 The nature of the bridging ligand in 1 is also of vital importance for the stability of 1 in solution. This is shown by further experiments, where we tried to connect two [Ge9(Hyp)2]2− clusters via other Cl-R-Cl units like ClMe2Si-O-SiMe2-O-SiMe2Cl, ClMe2Si-(CH2)2-SiMe2Cl, ClMe2Si-(CH2)6-SiMe2Cl, or ClMe2Si-C6H4-C6H4-
Figure 1. Molecular structure of [(Hyp)2Ge9-SiMe2-C6H4-SiMe2Ge9(Hyp)2K]− 1 within K1. Hydrogen atoms are omitted for clarity, and all carbon atoms are only shown as wire presentation for clarity; thermal ellipsoids are shown with 50% probability.11 Selected bond lengths [pm]: K1−Ge7:388.86(18), K1−Ge9:359.00(18), K1− Ge13:378.35(19), K1−Ge16:387.18(17), K1−Ge19:366.84(18), K1−C45:331.4(7), K1−C46:324.0(6), K1−C47:320.5(6), K1− C48:332.9(6), Ge4−Ge7:255.79(14), Ge4−Ge9:249.91(12), Ge7− Ge9:263.26(12), Ge13−Ge16:252.72(9), Ge16−Ge19:255.34(11), Ge4−Si4:233.3(2), Ge16−Si61:235.93(18), Si61−C46:188.5(6), C46−C47:139.7(8), C47−C48:139.1(8).
distances in 1 are similar to the ones in [(Tol)3K][Ge9(Hyp)3] (Tol = toluene), where the K−C distances vary from 310 to 340 pm.9 As also the Ge−K distances in 1 (359−388 pm) are comparable to the ones found in [(Tol)3K][Ge9(Hyp)3] (372 to 387 pm9), a quite similar bonding situation is realized for the potassium cation being thus mostly electrostatic in nature. However, within 1 two Ge9R3 clusters are linked together in a definite way via a bridging ligand. The nine germanium atoms within the two Ge9 units in 1 are arranged like the nido form of a monocapped square antiprism,12 as it is the case for the starting compound [Ge9(Hyp)2]2−, the Zintl anion Ge94−,13 and other disubstituted clusters such as [Ge 9 (CH CH2)2]2−.14 As every Ge9R3− unit in 1 exhibits 22 cluster bonding electrons (2n + 4; n = 9)15 1 obeys Wade’s rules.16 However, such an arrangement is unusual within metalloid [Ge9R3]− clusters, where normally an arrangement related to the closo form of a distorted tricapped trigonal prism is realized.17−19 Nevertheless the differences are small, and as to be seen in Table 1 the differences in the prism heights in 1 are between those found for [Ge9(Hyp)2]2− (closely related to the nido form) and [Ge9(Hyp)3]− (closely related to the closo form), which might be the result of the presence of the bridging substituent (vide infra). Within the crystal structure of K1 the [(Hyp)2Ge9-SiMe2C6H4-SiMe2-Ge9(Hyp)2K]− anions 1 are connected via potassium cations, which are further saturated by a THF molecule, leading to zigzag chains of 1 within the solid state 9694
DOI: 10.1021/acs.inorgchem.7b01186 Inorg. Chem. 2017, 56, 9693−9697
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Inorganic Chemistry
arrangement of the nine germanium atoms within the two Ge9R3 units in 1 is different with respect to all other known Ge9R3 clusters. Quantum chemical calculations further reveal a direct interaction, whereby HOMO−15 exhibits orbital contributions from both Ge9 units and the bridging C6H4 ligand. Further ongoing investigations will reveal the influence of this interaction onto the physical and chemical properties of this novel compound. 1 cannot be transferred intact into the gas phase via electrospray ionization. However, 1 is stable in solution and shows like [Ge9(Hyp)3]− a featureless UV/vis spectrum; that is, further insight into the photodynamic of metalloid group 14 clusters is possible and the issue of ongoing experiments.
SiMe2Cl. All these experiments failed, as the reactions only give complex product mixtures as indicted by complicated proton NMR spectra of the reaction solution and from which no product could be isolated yet. Nevertheless, in some cases first of all a promising simpler proton NMR spectrum is obtained from the reaction mixture, showing that first of all a quite selective metathesis reaction takes place. However, the spectrum gets more complicated by time, showing that the primary formed product, which might be the anticipated target molecule, is not stable in solution and slowly degrades.25 If the primarily formed products might be isolated at lower temperature or might be stabilized by the addition of other cations is not clarified yet and is within the scope of further ongoing experiments. To get a first insight into the bonding situation of 1 we performed quantum chemical calculation on 1, where the calculated structure fits quite well to the experimentally determined one.26,27 An analysis of the bonding within 1 further shows that the bonding electrons are strongly delocalized, as three center bonding components with shared electron numbers (SENs)28 up to 0.37 are obtained via an Ahlrichs−Heinzmann population analysis; that is, a similar bonding situation as observed within Ge9Hyp3−,20 is realized. However, the quantum chemical calculations further hint to an interaction of the two Ge9 units via the bridging ligand, which becomes obvious by an inspection of the molecular orbitals, where within HOMO−15 contributions from both Ge9 units and the bridging C6H4 linker are present (Figure 2).
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EXPERIMENTAL SECTION
General Considerations. Commonly used abbreviations: THF = tetrahydrofuran, Tol = toluene, Hyp = Si(SiMe3)3. All reactions were performed under nitrogen atmosphere using Schlenk techniques. THF was dried over sodium and pentane over CaH2. All organic solvents were freshly distilled under nitrogen atmosphere prior to use. Bruker DRX-250 and AV-400 spectrometers were used to obtain 1H, 13C, and 29 Si NMR spectra. 1H, 13C, and 29Si chemical shifts δ are given in parts per million and were referenced to Me4Si. NMR spectra were recorded at room temperature. K2[Ge9(Hyp)2] was prepared according to a previously described procedure.9 para-ClMe2Si-C6H4-SiMe2Cl was commercially available (Aldrich) and used as received. Synthesis of [(Hyp)2Ge9-SiMe2-C6H4-SiMe2-Ge9(Hyp)2K]K(THF) (K1). A THF solution (2 mL) of p-ClMe2Si-C6H4-SiMe2Cl (21 mg, 0.08 mmol) was added to 5 mL of a THF solution of K2[Ge9(Hyp)2] (200 mg, 0.16 mmol), and the reaction mixture was stirred for 1 h, which led to a quantitative and selective reaction according to NMR. The solvent was evaporated under vacuum, and the solid rest was extracted by 30 mL of pentane. Concentration and crystallization of the obtained extract yielded big orange-red crystals of [K(THF)][(Hyp)2Ge9-SiMe2-C6H4-SiMe2-Ge9(Hyp)2K] (94 mg; 45% yield). 1 H NMR (400 MHz, THF-d8): 0.27 ppm (s, 108H, SiMe3 groups of Hyp ligand), 0.48 ppm (s, 12H, Me groups of bridging ligand), 7.58 ppm (s, 4H, -C6H4-); 13C{1H} NMR (62.9 MHz, THF-d8): 3.26 ppm (s, SiMe3 groups of Hyp ligand), 8.17 ppm (s, Me groups of bridging ligand), 134.06 ppm (s, C-H of aromatic ring), 143.72 ppm (s, tert C of aromatic ring); 29Si NMR (50 MHz, THF-d8): −106.9 ppm (-Si(SiMe3)3), −9.4 ppm (m, J2(Si−H) = 6.5 Hz, -Si(SiMe3)3), 10.4 ppm (-SiMe2-). X-ray Structural Characterization. Crystals were mounted on the diffractometer at 150 K. The data were collected on a Bruker APEX II diffractometer employing monochromated Mo Kα (λ = 0.710 73 Å) radiation from a sealed tube and equipped with an Oxford Cryosystems cryostat. A semiempirical absorption correction was applied using the program SADABS. The structure was solved by direct methods and refined against F2 for all observed reflections. Programs used: SHELXS and SHELXL30 within the Olex2 program package.31 CCDC-1535453 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from the Cambridge Crystallographic Data Centre via www.ccdc.cam. as.uk/data_request/cif. In the unit cell, two very large solventcontaining voids (438 and 437 Å3) are found, which are treated with the SQUEEZE model32 to identify 79 electrons each, which is equal to two disordered THF molecules per void. [(Hyp) 2 Ge 9 -SiMe 2 -C 6 H 4 -SiMe 2 -Ge 9 (Hyp) 2 K]K(THF) K1. C50H132Ge18K2OSi18; Mr = 2639.99 g mol−1, crystal dimensions 0.376 × 0.297 × 0.09 mm3, space group P2(1)/c, a = 14.7983(3) Å, b = 26.8760(7) Å, c = 29.0837(7) Å, β = 91.6720(10), V = 11 562.2(5) Å3, Z = 4, ρcalc = 1.517 g cm−3, μMo = 4.885 mm−1, 2θmax = 50°, 164 295 reflections measured, 20 379 independent reflections (Rint = 0.0643), absorptions correction: semiempirical (min/max transmission 0.4943/0.7457), R1 = 0.0491, wR2 = 0.1371, Bruker APEXII diffractometer (Mo Kα radiation (λ = 0.710 73 Å), 150 K).
Figure 2. HOMO−15 of [(Hyp) 2 Ge 9 -SiMe 2 -C 6 H 4 -SiMe 2 Ge9(Hyp)2K]− 1.
The UV/vis spectrum of a THF solution of 1 shows no characteristic absorption feature (Figure S10 in the Supporting Information) and is thus comparable to the spectrum obtained for [Ge9(Hyp)3]−.29 Hence, further investigations on the photophysical properties of 1 including femtosecond pump− probe absorption spectroscopy will be necessary to identify differences and similarities of the physical properties of the metalloid germanium clusters 1 and [Ge9(Hyp)3]− after photoexcitation, giving further insight into the photodynamics of metalloid group 14 clusters.
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SUMMARY AND OUTLOOK We presented the synthesis and characterization of [(Hyp)2Ge9-SiMe2-C6H4-SiMe2-Ge9(Hyp)2K]− 1, the first compound where two Ge9(Hyp)2 subunits are connected via an organic linker. The nature of the organic linker is of central importance for the stability of 1, as all other tested bridging ligands only lead to degradation, however, sometimes after the formation of a primary unstable product in high amount. The 9695
DOI: 10.1021/acs.inorgchem.7b01186 Inorg. Chem. 2017, 56, 9693−9697
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Inorganic Chemistry Quantum Chemical Calculations. Quantum-chemical calculations were performed with the RI-DFT version of the Turbomole program package by employing the BP86-functional. The basis sets were of TZVPP quality. The electronic structure of 1 was analyzed with the Ahlrichs−Heinzmann population analysis based on occupation numbers.26 Details of the results (coordinates of the optimized structure and SENs) are given in the Supporting Information.
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Chem. 2002, 114, 3682−3704; Angew. Chem., Int. Ed. 2002, 41, 3532− 3554. (b) Mednikov, E. D.; Dahl, L. F. Syntheses, structures and properties of primarily nanosized homo/heterometallic palladium CO/PR3-ligated clusters. Philos. Trans. R. Soc., A 2010, 368, 1301− 1332. (c) Goswami, N.; Yao, Q.; Chen, T.; Xie, J. Mechanistic exploration and controlled synthesis of precise thiolate-gold nanoclusters. Coord. Chem. Rev. 2016, 329, 1−15. (d) Jin, R.; Zeng, C.; Zhou, M.; Chen, Y. Atomically Precise Colloidal Metal Nanoclusters and Nanoparticles: Fundamentals and Opportunities. Chem. Rev. 2016, 116, 10346−10413. (3) Schnepf, A. Metalloid Cluster Compounds of Germanium: Synthesis − Properties − Subsequent Reactions. Eur. J. Inorg. Chem. 2008, 2008, 1007−1018. (4) Yau, S. H.; Varnavski, O.; Goodson, T. Acc. Chem. Res. 2013, 46, 1506−1516. (5) (a) Cunningham, A.; Mühlig, S.; Rockstuhl, C.; Bürgi, T. Coupling of Plasmon Resonances in Tunable Layered Arrays of Gold Nanoparticles. J. Phys. Chem. C 2011, 115, 8955−8960. (b) BlancoLoimil, M.; Pardo, A.; Villar-Alvarez, E.; Martinez-Gonzalez, R.; Topete, A.; Barbosa, S.; Taboada, P.; Mosquera, V. Development of ordered metal nanoparticle arrangements on solid supports by combining a green nanoparticle synthetic method and polymer templating for sensing applications. RSC Adv. 2016, 6, 60502−60512. (6) Lahtinen, T.; Hulkko, E.; Sokolowska, K.; Tero, T.-R.; Saarnio, V.; Lindgren, J.; Pettersson, M.; Häkkinen, H.; Lehtovaara, L. Covalently linked multimers of gold nanoclusters Au102(p-MBA)44 and Au∼250(p-MBA)n. Nanoscale 2016, 8, 18665. (7) Bentlohner, M. M.; Klein, W.; Fard, Z. H.; Jantke, L.-A.; Fässler, T. F. Linking Deltahedral Zintl Clusters with Conjugated Organic Building Blocks: Synthesis and Characterization of the Zintl Triad [RGe9-CHCH-CHCH-Ge9-R]4−. Angew. Chem. 2015, 127, 3819− 3824; Angew. Chem., Int. Ed. 2015, 54, 3748−3753. (8) This reaction was introduced by Sevov et al. for the rational synthesis of the metalloid germanium cluster [Ge9(Hyp)3]− Li, F.; Sevov, S. C. Rational Synthesis of [Ge9{Si(SiMe3)3}3]− from Its Parent Zintl Ion Ge94−. Inorg. Chem. 2012, 51, 2706−2708. (9) Kysliak, O.; Schnepf, A. {Ge9[Si(SiMe3)3]2}2−: a starting point for mixed substituted metalloid germanium clusters. Dalton Trans. 2016, 45, 2404−2408. (10) Additionally, it is possible to start from the dianionic compound [Ge9(HypPh)2]2− to obtain the mixed substituted compound [Ge9(HypPh)2(Hyp)]− indicating that a large variety of different substituents might be used in this substitution chemistry.17 (11) A picture where also all carbon atoms are shown as thermal ellipsoids with 50% probability is given in the Supporting Information Figure S11. (12) A picture clarifying the relation of the arrangement of the germanium atoms in the Ge9 units to a monocapped square antiprism is given in the Supporting Information (Figure S13). (13) (a) Belin, C. H. E.; Corbett, J. D.; Cisar, A. Homopolyatomic Anions and Configurational Questions. Synthesis and Structure of the Nonagermanide (2-) and Nonagermanide (4-) Ions, Ge92‑ and Ge94‑. J. Am. Chem. Soc. 1977, 99, 7163−7169. (b) Ponou, S.; Fässler, T. F. Crystal Growth and Structure Refinement of K4Ge9. Z. Anorg. Allg. Chem. 2007, 633, 393−397. (14) Hull, M. W.; Sevov, S. C. Organo-Zintl Clusters Soluble in Conventional Organic Solvents: Setting the Stage for Organo-Zintl Cluster Chemistry. Inorg. Chem. 2007, 46, 10953−10955. (15) As the substituent-bound germanium atoms support three electrons for cluster bonding and the naked germanium atoms two, bearing a lone pair, every [Ge9R3]− unit in 1 has 22 clusters. (16) Wade, K. Structural and Bonding Patterns in Cluster Chemistry. Adv. Inorg. Chem. Radiochem. 1976, 18, 1−66. (17) Kysliak, O.; Kunz, T.; Schnepf, A. Metalloid Ge9R3− Clusters with Various Silyl Substituents: From Shielded to Open Cluster Cores. Eur. J. Inorg. Chem. 2017, 2017, 805−810. (18) Kysliak, O.; Schnepf, A. Reference Module in Chemistry, Molecular Sciences and Chemical Engineering; Reedijk, J., Ed.; Elsevier: Waltham, MA, 2017, doi:10.1016/B978-0-12-409547-2.13891-0.
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.7b01186. Spectra obtained by 1H, 13C, and 29Si NMR; results of DLS measurements; discussion of mass spectrometry and results; comparison of measured and simulated isotopic patterns; UV−vis spectrum; illustrated molecular structures; tabulated calculated coordinates and SENs, comparison of measured and calculated distances between atoms (PDF) Accession Codes
CCDC 1535453 contains 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_
[email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
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AUTHOR INFORMATION
Corresponding Author
*Phone: +49 (7071) 29−76635. Fax: +49 (7071) 28−2436. Email:
[email protected]. ORCID
Andreas Schnepf: 0000-0002-7719-7476 Funding
We are grateful to the Deutsche Forschungsgemeinschaft (DFG) for financial support. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS The computational studies were supported by the bwHPC initiative and the bwHPC-C5 project provided through the associated compute services of the JUSTUS HPC facility at the Univ. of Ulm. bwHPC and bwHPC-C5 (http://www.bwhpcc5.de) are funded by the Ministry of Science, Research and the Arts Baden-Württemberg (MWK) and the DFG. We thank Prof. P. Roesky for measurement time at the Orbitrap mass spectrometer at KIT and P. Smie for her help during the measurement.
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DEDICATION Dedicated to Professor Gudat on the occasion of his 60th birthday. REFERENCES
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Inorganic Chemistry
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DOI: 10.1021/acs.inorgchem.7b01186 Inorg. Chem. 2017, 56, 9693−9697
