Oxygen-Centered Hexatantalum Tetradecaimido Cluster Complexes
| Autor: | Robert G. Bergman, John Arnold, Laura L. Anderson, Jamin L. Krinsky |
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| Rok vydání: | 2007 |
| Předmět: |
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Molecular Magnetic Resonance Spectroscopy Chemistry Inorganic chemistry Tantalum chemistry.chemical_element Electronic structure Crystallography X-Ray Oxygen Article Inorganic Chemistry Delocalized electron Crystallography chemistry.chemical_compound Aniline Cluster (physics) Spectrophotometry Ultraviolet Molecular orbital Physical and Theoretical Chemistry Oxidation-Reduction Stoichiometry |
| Zdroj: | Inorganic Chemistry. 47:1053-1066 |
| ISSN: | 1520-510X 0020-1669 |
| Popis: | The syntheses and characterization of several octahedral hexatantalum cluster compounds of formula (ArN)14Ta6O are described (Ar = Ph, p-MeC6H4, p-MeOC6H4, p-t-BuC6H4, p-BrC6H4, m-ClC6H4). Treatment of Bn3Ta=N-t-Bu (Bn = CH2C6H5) or pentakis(dimethylamido)tantalum with an excess of the appropriate aniline and stoichiometric water or tantalum oxide afforded varying yields of arylimido clusters. The structures of two species were confirmed by X-ray diffraction (XRD), while the identity of the central oxygen atom was elucidated by electrospray mass spectrometry (MS) using 17O/18O-enriched material. The title species are very air- and moisture-sensitive but quite thermally stable in solution. Experimentally determined optical properties and oxidation/reduction potentials, as well as some computational results, indicate that they possess an electronic structure wherein the highest occupied molecular orbitals are ligand-centered, while the lowest unoccupied orbitals are metal-centered and delocalized throughout the tantalum cage. Whereas chemical oxidation resulted in cluster decomposition, reduction with decamethylcobaltocene yielded stable salts of formula [Cp*2Co][(ArN)14Ta6O] (Ar = Ph, Ar = p-MeC6H4). Small-molecule reactivity studies on one of these clusters showed that its imido functionalities are moderately reactive toward oxide donors but inert with respect to metallaheterocycle-forming processes. Clean imido/oxo exchange was observed with aldehydes and ketones, leading cleanly to organic imines with no soluble byproducts being observed. This exchange was also observed with a rhenium oxo compound (generating an imidorhenium complex as the only soluble species). All 14 imido groups were transferred in these reactions, and no mixed-ligand cluster intermediates were ever observed. |
| Databáze: | OpenAIRE |
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