Synthesis and characterisation of pseudocloso iridium and ruthenium diphenyl carbaboranes. Molecular structures of 1,2-Ph(2)-3-(eta-C6H6)-3,1,2-pseudocloso-RuC2B9H9 and 1,2-Ph(2)-3-(cym)-3,1,2-pseudocloso-RuC2B9H9 (cym equals p-cymene) and individual gauge for localised orbitals calculations on carbametallaboranes

The syntheses and characterisations of 1,2-Ph(2)-3-(eta-C(5)Me(5))-3,1,2-pseudocloso-IrC2B9H9 1, 1,2-Ph(2)-3-(eta-C6H6)-3,1,2-pseudocloso-RuC2B9H9 2, 1,2,-Ph(2)-3-(cym)-3,1,2-pseudocloso-RuC2B9H9 (cym = p-cymene) 3 and 1,2-Ph(2)-3-(eta-C(6)Me(6))-3,1,2-pseudocloso-RuC2B9H9 4 are reported from the reactions between Tl-2[7,8-Ph(2)-nido-7,8-C2B9H9] and either [{IrCl2(C(5)Me(5))}(2)] or the appropiate [{RuCl2(arene)}(2)] species. By B-11 NMR spectroscopy all these compounds have pseudocloso geometries, in which the C(1)... C(2) connectivity is broken and an approximately square M(3)C(1)B(6)C(2) face is generated. Crystallographic studies on 2 and 3 confirm this suggestion. It is suggested that distortion in these species arises from steric crowding between the C-phenyl substituents, forced to adopt conformations with high theta values by the presence of the eta-bonded substituent at M(3). Individual gauge for localised orbitals calculations, reported for the first time on transition-metal heteroboranes, reasonably reproduce the (previously assigned) B-11 NMR chemical shifts of 3-(eta-C(5)Me(5))-3,1,2-closo-RhC2B9H11, and allow a tentative assignment of those of 1,2-Ph(2)-3-(eta-C(5)Me(5))-3,1,2-pseudocloso-RhC2B9H9.