Reaction of cyclopentadienyl ruthenium complexes with a carborane anion: effect of the spectator ligands on the substitution site

The reaction of cyclopentadienyl ruthenium complexes of the type [RuCl(Cp)L1L2] (L1, L2 ) PPh3, PMe2Ph, PMePh2; L1L2 ) dppe; L1L2 ) COD; L1 ) CO, L2 ) PPh3) with Licarb (Hcarb ) 2-Me-1,2-dicarba-closo-dodecaborane) gives two types of complexes, [Ru(H)(C5H4-carb)L1L2] or
[Ru(carb)(Cp)-L1L2], depending on the nature of the coordination set. The structures of [Ru(carb)(Cp)(PMe2Ph)2] and [RuCl(eta5-C5Me4H)(PMe2Ph)2] have been determined by single-crystal crystallography. The role played by the ligand set on the site of nucleophilic attack is discussed in light of the steric crowding and electronic density at the metal center.