Neighboring Group Participation of Halo and Aryl Groups in the Stoichiometric and Catalytic Reactions of Olefins with Transition-Metal Hydrides and a New Route to Arene Complexes

Article abstract of DOI:10.1021/ja00322a029

BF4 (1) reacts with ArCH=CH2 to give 6-ArEt)L2>BF4 (2, Ar=Ph, 2,6-Me2C6H3, p-MeOC6H4, PhCH2, Ph(CH2)2, 2,6-Cl2C6H3, and 2-XC6H4 ).For the first three substrates, a neighboring group participation of the aryl group via an η³-benzyl intermediate is proposed.For the next two, isomerisation takes place to give a styrene derivative which then reacts as above.For the halogen-containing substrates the unusual intermediates 3-XC6H4CH=CH2)L2>BF4 are observed, in which the substrate chelates to the metal via the (C=C) and halo groups.These are rare examples of both a halocarbon complex and an olefin dihydrido complex.The high branched:linear isomer ratios generally observed in the hydroformylation and hydrosilation of styrene are interpreted in terms of neighboring group participation via an η³-benzyl intermediate.Halo and aryl groups are suggested as candidates for study in connection with directing effects and asymmetric induction in homogeneous catalysis.