Tri-1-Methallyl- and 1-Methallyl-Butadiene Group IV Transition Metal Complexes

Reaction of Cp´MCl3 (Cp´ = η5-C5(CH3)5; M = Ti, Zr, Hf) with 2-butenylmagnesium bromide at low temperatures gives Cp´M(1-methallyl)3, which is readily converted into Cp´M(η3-1-methallyl)(η4-butadiene) on heating. Only Cp´Hf(1 methallyl)3 could be isolated; it is fluxional and its NMR and IR spectra indicate that it consists of a complex mixture of isomers containing interconverting η1- and η3-1-methallyl groups. The compounds Cp´M(η3-C4H7)(η4-C4H6) are much more thermally stable; they show fluxional behaviour, but this is limited to the η3-1-methallyl group. These complexes are very reactive towards a large variety of organic substrates.