α- and β-Agostic Alkyl-Titanocene Complexes

Reaction of [Cp2Ti(Me)(CD2Cl2)](+) (I) with 3,3-dimethyl-1-butene in oCD(2)Cl(2) at 205 K produces the alpha-agostic insertion product [(Cp2TiCH2CHMeBu)-Bu-t](+) (II), in which the chirality at C(2) induces preferential agostic binding of one of the diastereotopic alpha-H atoms; subsequent coordination of ethyl ether to II leaves the alpha-agostic interaction weakened but intact. On warming, II undergoes beta-hydrogen elimination and the resulting hydride reacts further with excess 3,3-dimethyl-1-butene to form the beta-agostic species [(Cp2TiCH2CH2Bu)-Bu-t](+). NMR data and calculated (DFT) energies support the assignments.