Reactions of the Lithiated Diphosphine tBu2P-P(SiMe3)Li with [(eta6-C6H6)RuCl2]2in the Presence of Tertiary Phosphines

tBu2P-P(SiMe3)Li reacted with [(eta6-C6H6)RuCl2]2 at -40 °C in the presence of PR3 (PR3 = PEt3, PEt2Ph, PEtPh2) by the nucleophilic addition of the tBu2P-P(SiMe3) moiety to the benzene ring to yield solely the complexes [(R3P)2Ru(Cl){eta5-C6H6(Me3SiP-PtBu2)}] (1). These products decomposed slowly at ambient temperature to yield benzene, Ru clusters, and small amounts of the dinuclear ruthenium complexes [{(R3P)2Ru}2(mu,eta2:2-P2)2Ru(PR3)2] (Ru-Ru) (6). Single-crystal X-ray diffraction studies of [(PhEt2P)2Ru(Cl){eta5-C6H6(Me3SiP-PtBu2)}] (1b) and [(Ph2EtP)2Ru(Cl){eta5-C6H6(Me3SiP-PtBu2)}] (1c) revealed that the addition of the tBu2P-P(SiMe3) group occurred through an exo pathway. Complex 6a (R = Et) displays a planar rectangular P4 system consisting of two P2 units and a Ru-Ru distance that lies in the range of a single bond.