Coordination of the nido-Carboranyldiphosphine Ligand to Ruthenium(II): The First Example of the Tricoordinating Capacity of the 7,8-(PPh2)2-7,8-C2B9H10 Moiety

Reaction of [RuH(AcO)(PPh 3 ) 3 ] and [NMe 4 ][7,8-(PPh 2 ) 2 -7,8-C 2 B 9 H 10 ] in methanol yields [RuH(7,8-(PPh 2 ) 2 -7,8-C 2 B 9 H 10 )(PPh 3 ) 2 ] (1). The reaction of [RuCl 2 (PPh 3 ) 3 ] and [NMe 4 ][7,8-(PPh 2 ) 2 -7,8-C 2 B 9 H 10 ] in a 1:1 or 1:2 ratio in methanol yields [RuX(7,8-(PPh 2 ) 2 -7,8-C 2 B 9 H 10 )(PPh 3 ) 2 ] (X = Cl, H) (2). NMR spectroscopic analyses of 1 and 2 indicate that the centers have an octahedral geometry and the carborane acts as a tricoordinating ligand to ruthenium(II) by means of P-Ru, B(11)-H→Ru and B(2)-H→Ru agostic bonds. A chloride or hydride and two PPh 3 ligands complete the coordination sphere of the metal. The formation of two B-H→Ru agostic bonds rather than a second P-Ru bond appears to be due to steric factors. Reaction of [NMe 4 ][7,8-(PPh 2 ) 2 -7,8-C 2 B 9 H 10 ] with [RuCl 2 (PMePh 2 ) 4 ] in ratios of 1:1 and 2:1 in methanol yields complexes [Ru(7,8-(PPh 2 ) 2 -7,8-C 2 B 9 H 11 ) 2 ] (3) and [RuH(7,8-(PPh 2 ) 2 -7,8-C 2 B 9 H 11 ) 2 ] (4) respectively, which incorporate two nido-carboranylphosphine ligands.