Eta(5)-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)-((t)Bu(2)MeSi)(3)Si(3)C(2)Et(2)](-) 1(-)*[Li(+)(thf)] reacted with an equivalent amount of Rh(CO)(2)(acac) in toluene to form the half-sandwich (trisilacyclopentadienyl)dicarbonylrhodium complex [eta(5)-((t)Bu(2)MeSi)(3)Si(3)C(2)Et(2)]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 of (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 Si(3)C(2) five-membered ring. Reaction of 1(-)*[Li(+)(thf)] with 0.25 equiv of [Cp*RuCl](4) (Cp* = eta(5)-C(5)Me(5)) resulted in the formation of the sandwich complex Cp*Ru[eta(5)-((t)Bu(2)MeSi)(3)Si(3)C(2)Et(2)] 3 as the heavy analogue of ruthenocene.