η5-1,2,3-Trisilacyclopentadienyl - A Ligand for Transition Metal Complexes: Rhodium Half-Sandwich and Ruthenium Sandwich

The lithium salt of 1,2,3-trisilacyclopentadienide [eta(5)-((Bu2MeSi)-Bu-t)(3)Si3C2Et2](-) 1(-)center dot[Li+(thf)] reacted with an equivalent amount of Rh(CO)(2)(acac) in toluene to form the half-sandwich (trisilacyclopentadienyl)dicarbonylrhodium complex [eta(5)-((Bu2MeSi)-Bu-t)(3)Si3C2Et2]Rh(CO)(2) 2. pi-Electron delocalization in the trisilacyclopentadienyl ring in 2 was manifested in the shielding of the ring atoms upon complexation, as well as by the observation (1)J(Rh-c) and (1)J(Rh-Si) coupling constants. In the solid state, cyclic delocalization in 2 was seen in the diagnostic eta(5)-coordination of the heavy cyclopentadienyl ring to the Rh center and the remarkable flattening of the Si3C2 five-membered ring. Reaction of 1(-)center dot[Li+(thf)] with 0.25 equiv of [Cp*RuCl](4) (Cp* = eta(5)-C5Me5) resulted in the formation of the sandwich complex Cp*Ru[eta(5)-((Bu2MeSi)-Bu-t)(3)Si3C2Et2] 3 as the heavy analogue of ruthenocene