Chlorinated Hypoelectronic Dimetallaborane Clusters: Synthesis, Characterization, and Electronic Structures of (η5-C5Me5W)2B5HnClm (n = 7, m = 2 and n = 8, m = 1).

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]