Synthesis and characterisation of pseudocloso iridium and ruthenium diphenyl carbaboranes. Molecular structures of 1,2-Ph₂-3-(η-C₆H₆)-3,1,2-pseudocloso-RuC₂B₉H₉ and 1,2-Ph₂-3-(cym)-3,1,2-pseudocloso-RuC₂B₉H₉(cym =p-cymene) and individual gauge for localised orbitals calculations on carbametallaboranes

The syntheses and characterisations of 1,2-Ph₂-3-(η-C₅Me ₅)-3,1,2-pseudocloso-IrC₂B₉H₉ 1, 1,2-Ph₂-3-(η-C₆H ₆)-3,1,2-pseudocloso-RuC₂B₉H₉ 2, 1,2-Ph₂-3-(cym)-3,1,2-pseudocloso-RuC₂B₉H ₉ (cym = p-cymene) 3 and 1,2-Ph₂-3-(η-C₆Me ₆)-3,1,2-pseudocloso-RuC₂B₉H₉ 4 are reported from the reactions between Tl₂[7,8-Ph₂-nido-7,8-C₂B₉H ₉] and either [{IrCl₂(C₅Me₅)}₂] or the appropriate [{RuCl₂(arene)}₂] species. By ¹¹B 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 θ values by the presence of the η-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) ¹¹B NMR chemical shifts of 3-(η-C₅Me₅)-3,1,2-closo-RhC₂B ₉H₁₁, and allow a tentative assignment of those of 1,2-Ph₂-3-(η-C₅Me ₅)-3,1,2-pseudocloso-RhC₂B₉H₉.