Transition metal–carbon bonds. Part VII. The formation of π-allylic–palladium complexes from allenes and palladium halides and the reversed reactions

Abstract

The formation of bridged-chloro- 2-chloroprop-2-enyl- and β-(3-chloroprop-1-en-2-yl)allyl-palladium(II) complexes by reacting allene with palladium(II) chloride complexes are described. Similar reactions of methylallene and 1,1-dimethylallene are also described. The resultant bridged-chloro-π-allylic complexes undergo reactions such as metathesis and conversion to monomeric acetylacetonates and also bridged splitting reactions with amines or tertiary phosphines. Under certain conditions, the β-halo π-allylic complexes can eliminate allenes on reaction with ammonia or tertiary phosphines. The mechanisms of the formation of π-allylic complexes from allenes and palladium(II) halide complexes are discussed as are the reversed reactions, e.g., elimination of allene from β-haloallyl complexes. Nuclear magnetic resonance data are given.