Fine Tuning of Metallaborane Geometries: Chemistry of Metallaboranes of Early Transition Metals Derived from Metal Halides and Monoborane Reagents |
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| Authors: | Shubhankar Kumar Bose K. Geetharani V. Ramkumar Shaikh M. Mobin Sundargopal Ghosh Dr. |
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| Affiliation: | 1. Department of Chemistry, Indian Institute of Technology Madras, Chennai 600?036 (India), Fax: (+91)?44‐2257‐4202;2. National Single Crystal X‐ray Diffraction Facility, Indian Institute of Technology, Bombay, Mumbai 400?076 (India) |
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| Abstract: | Reaction of [CpnMCl4?x] (M=V: n=x=2; M=Nb: n=1, x=0) or [Cp*TaCl4] (Cp=η5‐C5H5, Cp*=η5‐C5Me5), with [LiBH4?thf] at ?70 °C followed by thermolysis at 85 °C in the presence of [BH3?thf] yielded the hydrogen‐rich metallaboranes [(CpM)2(B2H6)2] ( 1 : M=V; 2 : M = Nb) and [(Cp*Ta)2(B2H6)2] ( 3 ) in modest to high yields. Complexes 1 and 3 are the first structurally characterized compounds with a metal–metal bond bridged by two hexahydroborate (B2H6) groups forming a symmetrical complex. Addition of [BH3?thf] to 3 results in formation of a metallaborane [(Cp*Ta)2B4H8(μ‐BH4)] ( 4 ) containing a tetrahydroborate ligand, [BH4]?, bound exo to the bicapped tetrahedral cage [(Cp*Ta)2B4H8] by two Ta‐H‐B bridge bonds. The interesting structural feature of 4 is the coordination of the bridging tetrahydroborate group, which has two B? H bonds coordinated to the tantalum atoms. All these new metallaboranes have been characterized by mass, 1H, 11B, and 13C NMR spectroscopy and elemental analysis and the structural types were established unequivocally by crystallographic analysis of 1 – 4 . |
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| Keywords: | cluster compounds metallaboranes niobium tantalum vanadium |
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