Brunner, Henri and Cattey, Helene and Evrard, David and Kubicki, Marek M. and Mugnier, Yves and Vigier, Estelle and Wachter, Joachim and Wanninger, Robert and Zabel, Manfred (2002) Bis(eta-tert-butylcyclopentadienyl)hydridoniobium ditelluride, a convenient reagent for the synthesis of polynuclear metal telluride complexes. EUROPEAN JOURNAL OF INORGANIC CHEMISTRY (6). pp. 1315-1325. ISSN 1434-1948
Full text not available from this repository.Abstract
Reaction of [Cp'2NbH3] (Cp' = tBuC(5)H(4)) with Te powder in THF gives [CP'Nb-2(Te-2)H] (1) and [Cp'6Nb4Te4O] (2). The yield of I varies between 10 and 81% depending on the degree of oxygen contamination of the reagents. Complexes I and 2 react with [Cr(CO)(5)THF] to give [Cp'Nb-2(Te-2)H.Cr(CO)(5)] (3) and [Cp'6Nb4Te4O.2Cr(CO)(5)] (4), respectively. The crystal structures of 2-4 have been determined. In 3 a Te-2 unit and an H ligand are coordinated to a bent niobocene moiety; the Cr(CO)5 group is attached to the lateral Te atom, The molecular cores of 2 and 4 are practically identical in that they contain two planar Nb2Te2 rings connected by a nearly linear oxygen bridge. Each of the "outer" Nb atoms bears two Cp' ligands, whereas the "inner" Nb atom only has one such ligand. An additional structural feature in 4 is two Cr(CO)(5) groups, attached to one Te bridge of each Nb2Te2 ring. Thermolysis of 3 leads to the formation of diamagnetic [CP'4Nb2Te2] (5), which also contains a planar Nb2Te2 core. The relatively long transannular Nb-Nb distance (3.647 Angstrom) is consistent, according to DFT calculations, with a through-space Nb-Nb coupling. Complex 5 reacts with CH3I with successive methylation of both Te bridges to give [CP'4Nb2Te(CH3Te)]I ([6]I) and [Cp'Nb-4(2)(CH3Te)(2)]I-2 ([7]I-2). The crystal structure of [7]I-2 may be derived from that of 5, the incoming CH3 groups being fixed at the TO bridges in a trans position. H-1 NMR spectroscopic investigations reveal a restricted rotation around the Cp'-Nb bonds in 2 and 5 at -90 degreesC and in 4 and [7]I-2 at ambient temperature. Electrochemical studies have been carried out on 5, [6]I, and [7]I-2, showing that all compounds undergo two reversible one-electron reduction steps. The reduction potential decreases by ca. 1.6 V when going from 5 to [7]I-2. There is also a clear linear correlation between the reduction potentials measured for 5 to [7]I-2 and the energies of the corresponding LUMO's calculated at the DFT/B3LYP level. These LUMO's bear some 70% contribution from both Nb atoms and, consequently, the reduction processes mainly operate at both metallic centers. ((C) Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002).
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | EFFECTIVE CORE POTENTIALS; M = CR; CRYSTAL-STRUCTURES; MOLECULAR CALCULATIONS; METALLOCENE COMPLEXES; NIOBOCENE LIGANDS; REACTIVITY; SE; STABILIZATION; FRAGMENTS; niobium; tellurium; polynuclear complexes; cyclopentadienyl complexes; electrochemistry |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Anorganische Chemie > Alumni or Retired Professors > Arbeitskreis Dr. Joachim Wachter Chemistry and Pharmacy > Institut für Anorganische Chemie > Alumni or Retired Professors > Prof. Dr. Henri Brunner |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 25 Oct 2021 11:31 |
| Last Modified: | 25 Oct 2021 11:31 |
| URI: | https://pred.uni-regensburg.de/id/eprint/40187 |
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