Structures and properties of nonchelated, d0 alkyl alkene complexes of the type [Cp2ZrMe(alkene)]+: elusive intermediates during Ziegler-Natta polymerizations of alkenes.

Caught in the act: An alkyl alkene Zr(IV) complex (see picture; Cp = C(5)H(5)) has been synthesized and characterized for the first time. The alkene bonding mode is highly asymmetric, and C2 is quite carbocationic. There is also evidence for rotation about the C1-C2 bond. This extremely unusual complex provides an exemplar of previously unknown intermediates in Ziegler-Natta and carbocationic polymerization reactions of alkenes.