Chlorinated hypoelectronic dimetallaborane clusters: Synthesis, characterization, and electronic structures of (η⁵-C₅Me₅W)₂B₅H_nCl_m (n = 7, m = 2 and n = 8, m = 1)

Abstract

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.