Preparation and Reactions of Cyclic and Acyclic Allene Complexes of Zirconocene

Article abstract of DOI:10.1016/0040-4020(94)01128-M

The zircone ?-complex of 3-methyl-1,2-butadiene (1,1-dimethylallene) cannot be prepared by simple ligand substitution due to rapid coupling of the initially formed complex with the unreacted allene.This problem was circumvented by generating the allene complex by β-hydrogen elimination from a pre-formed sigma complex.This appears to be a potentially general way to prepare allene complexes of zirconocene if the allene precursor has no cis-vinyl hydrogen.This method has been successfully used to prepare zirconocene complexes of 3-methyl-1,2-cycloheptadiene, 3-methyl-1,2-cyclohexadiene and 4-phenyl-1,2,3-cyclohexatriene.Attempts to prepare a complex of 3-methyl-1,2-cyclopentadiene failed.Selected reactions of two of these cumulene complexes and their coupling products are reported.