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Title: Metallaboranes of the early transition metals: Direct synthesis and characterization of [{(?5-C5Me5)Ta} 2BnHm] (n=4, m = 10; n = 5, m = 11), [{(?5-C5Me5)Ta}2B 5H10(C6H4CH3)]
Authors: Bose, S.K.
Geetharani, K.
Varghese, B.
Mobin, S.M.
Ghosh, S.
Keywords: Boron; Boron compounds; Chromium; High performance liquid chromatography; Hydrogen; Mass spectrometry; Molybdenum; Nuclear magnetic resonance; Nuclear magnetic resonance spectroscopy; Reaction kinetics; Rhenium; Rhenium compounds; Tantalum compounds; Toluene; Transition metals; Boranes; Cluster compounds; Crystallographic analyses; Direct syntheses; Early transition metals; Electronically unsaturated; Elemental analyses; Hydride ligands; Isostructural; Metallaboranes; Nmr spectroscopies; Structural types; Trigonal bipyramids; Tantalum
Issue Date: 2008
Citation: Chemistry - A European Journal, 14(29), 9058-9064
Abstract: Reaction of [Cp*TaCl4] (Cp* = ?5- C5Me5) with a sixfold excess of LiBH4� thf followed by BH3�thf in toluene at 100�C led to the isolation of hydrogen-rich metallaboranes [(Cp*Ta)2B 4H10] (1), [(Cp*Ta)2B5H 11] (2), [(Cp*Ta)2B5H10) (C6H4CH3)] (3), and [(Cp*TaCl) 2B5H11] (4) in modest yield. Compounds 1-3 are air- and moisture-sensitive but 4 is reasonably stable in air. Their structures are predicted by the electron-counting rules to be a bicapped tetrahedron (1), bicapped trigonal bipyramids (2, 3), and a nido structure based on a closo dodecahedron (4). Yellow tantalaborane 1 has a nido geometry with C2v symmetry and is isostructural with [(Cp*M)2B4H 8] (M = Cr and Re); whereas 2 and 3 are C3v-symmetric and isostructural with [(Cp*M)2B5H9] (M = Cr, Mo, W) and [(Cp*ReH)2B5Cl5]. The most remarkable feature of 4 is the presence of a hydride ligand bridging the ditantalum center to form a symmetrical tantalaborane cluster with a long Ta-Ta bond (3.22 �). Cluster 4 is a rare example of electronically unsaturated metallaborane containing four TaHB bonds. All these new metallaboranes have been characterized by mass spectrometry, 1H, 11B, and 13C NMR spectroscopy, and elemental analysis, and the structural types were unequivocally established by crystallographic analysis of 1-4. � 2008 Wiley-VCH Verlag GmbH & Co. KGaA.
ISSN: 9476539
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