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The reaction of the [(η5-C5Me5)MoCl4] complex with [LiBH4·THF] in toluene at -70 °C, followed by pyrolysis at 110 °C, afforded dark brown [(η5-C5Me5Mo)3MoB9H18], 2, in arallel with Ihe known [(η5-C5Me5Mo)2B5H9], 1. Compound 2 has been charactedzed in solution by ¹H, 11B, and 13C NMR spectroscopy and elemental analysis, and the structural types were unequivocally eslablished by crystallographic studies. The title compound represents a novel class of vertex-fused clusters in which a Mo atom has been fused in a perpendicular fashion between two molybdaborane clusters. Electronic structure calculations employing density functional theory yield geometdes in agreement with the structure determinations, and on grounds of density functional theory calculations, we have analyzed the bonding patterns in the structure. [ABSTRACT FROM AUTHOR]

Pyrolysis of (η5-C5Me5WH3)B4H8, 1, in the presence of excess BHCl2·SMe2 in toluene at 100 °C led to the isolation of (η5-C5Me5W)2B5H9, 2, and B−Cl inserted (η5-C5Me5W)2B5H8Cl, 3, and (η5-C5Me5W)2B5H7Cl2, 4−7 (four isomers). All the chlorinated tungstaboranes were isolated as red and air and moisture sensitive solids. These new compounds have been characterized in solution by 1H, 11B, 13C NMR, and the structural types were unequivocally established by crystallographic analysis of compounds 3, 4, and 7. Density functional theory (DFT) calculations were carried out on the model molecules of 3−7 to elucidate the actual electronic structures of these chlorinated species. On grounds of DFT calculations we demonstrated the role of transition metals, bridging hydrogens, and the effect of electrophilic substitution of hydrogens at B−H vertices of metallaborane structures. Reaction of (η5-C5Me5ReH2)2B4H4 with BHCl2·SMe2 led to the isolation of (η5-C5Me5ReH)2B5Cl5, while (η5-C5Me5WH3)B4H8 and an in situ generated intermediate, generated from (η5-C5Me5Mo)Cl4, and LiBH4, offer only partial chlorination at B−H vertices in (η5-C5Me5M)2B5H9 (M = W, Mo). DFT calculations were carried out on the model molecules of these chlorinated species; we demonstrated the role of transition metals, bridging hydrogens, and the effect of electrophilic substitution of hydrogens at B−H vertices of (η5-C5Me5M)2B5H9 (M = W, Mo). [ABSTRACT FROM AUTHOR]

Abstract: Reaction of (η5-C5Me5)MoCl4 with 6-fold excess of LiBH4·thf followed by pyrolysis with BHCl2·SMe2 in toluene at 90°C yielded known (η5-C5Me5Mo)2B5H9 (1) and B-Cl inserted (η5-C5Me5Mo)2B5H8Cl (2), (η5-C5Me5Mo)2B5H7Cl2 (3–5, three isomers) and (η5-C5Me5Mo)2B5H5Cl4 (6). In addition, reaction of (η5-C5Me5Mo)2B5H9 with 5-fold excess of n-BuLi followed by excess of MeI in THF yielded B-Me inserted metallaboranes (η5-C5Me5Mo)2B5H7(CH3)2 (7, 8 two isomers) and (η5-C5Me5Mo)2B5H6(CH3)3 (9, 10 two isomers). Isolated yields of 2–6 are poor but 7–10 are modest to good. Compounds 2–10 can be viewed as bicapped closo trigonal bipyramidal geometry. All the new compounds have been characterized in solution by IR, 1H, 11B, 13C NMR and mass spectroscopy as simple substitution derivatives of (η5-C5Me5Mo)2B5H9 and the structural types were unequivocally established by crystallographic analysis of compounds 2, 3, 5 and 6. [Copyright &y& Elsevier]