Reaction paths and mechanisms in the catalytic cycloaddition of allene over nickel(0) template systems

Abstract

Catalytic cycloadditions of allene, CH₂CCH₂, have been effected with a variety of nickel(0)–phosphorus ligand systems. The selective catalytic reaction path leading to the cyclotetramer, cyclotetramer, or cyclopentamer depends primarily on the nature of the ligands. Intermediate nickel(0) complexes containing the linear trimer (C₉H₁₂) or tetramer (C₁₂H₁₆) have been detected spectroscopically or isolated by stabilisation with phosphorus ligands. On the basis of the structures of the isolated complexes and kinetics, multistep reaction paths are described and the roles of the phosphorous ligands in these catalysts discussed.