(ETA(1)-PENTAMETHYLCYCLOPENTADIENYL)SILYL COMPLEXES OF RUTHENIUM - PREPARATION, REACTIVITY, AND X-RAY CRYSTAL-STRUCTURE OF CP(PME(3))(2)RUSICL2(ETA(1)-CP-ASTERISK)

The reaction of Cp(PMe(3))(2)RuCH(2)SiMe(3) (1) with (eta(1)-Cp)SiHCl 2 in refluxing toluene produces silyl Cp(PMe(3))(2)RuSiCl2(eta(1)-Cp) (2) in good yields; Cp(PMe(3))(2)RuSiCl3 (3) is a minor product of th is reaction. The Cp group in 2 is sigma-bound to the silicon and is ' 'static'' on the NMR time scale at room temperature. The eta(1)-Cp co nfiguration in 2 was confirmed by a single-crystal X-ray diffraction s tudy. In the structure of 2, a ''three-legged piano stool'' geometry i s observed around ruthenium whereas the silicon adopts a distorted tet rahedral geometry. The eta(1)-CP group on silicon is in an anti relat ionship with one of the phosphines on ruthenium (dihedral angle = 179. 5(3)degrees). Complex 2 exhibits reactions involving chloride substitu tion, Si-Cp bond cleavage, and Ru-Si bond cleavage. The reaction of 2 with LiAlH4 produces Cp(PMe(3))(2)RuSiH2(eta(1)-Cp) (6) in which the eta(1)-Cp group is more mobile compared to 2. The Si-Cp* bond of 2 i s readily cleaved by acid (i.e HCl(g), pyridinium chloride) to give 3 and pentamethylcyclopentadiene. Methanolysis of 2 cleaves the Ru-Si bo nd and gives the dihydride [Cp(PMe(3))(2)RuH2]Cl in nearly quantitativ e yields.