THE FORMATION AND STRUCTURES OF THE METHYL-BRIDGED COMPLEXES CP-ASTERISK-TIME(2)(MU-ME)B(C6F5)(3) AND SK-TIME(2)(MU-ME)TIME(2)CP-ASTERISK][MEB(C6F5)(3)]

Reaction of the compound CpTiMe(3) (Cp* = eta(5)-pentamethylcyclopent adienyl) with the potent Lewis acid B(C6F5)(3) results in methyl carba nion abstraction from the titanium and formation of the corresponding complex CpTiMe(2)(mu-Me)B(C6F5)(3), in which a methyl group bridges t he titanium and boron atoms. The isotopically labelled compounds CpTi (CH2D)(3), CpTi(CH2D)(2)(mu-CH2D)B(C6F5)(3), Cp*Ti((CH3)-C-13)(3), an d CpTi((CH3)-C-13)(2)(mu-(CH3)-C-13)B(C6F5)(3) have also been prepare d to provide NMR probes of the possibility of alpha-agostic bonding in these compounds, and while the answer appears to be 'no', a caveat on the use of this type of experiment is proposed. The compounds CpTiMe (3) and CpTiMe(2)(mu-Me)B(C6F5)(3) react further to form the novel bu t unstable methyl-bridged species [CpTiMe(2)(mu-Me)TiMe(2)Cp*][MeB(C6 F5)(3)], which has been characterized by H-1 and C-13{H-1} NMR spectro scopy.