Pt^II-Catalyzed Ethylene Hydrophenylation: Influence of Dipyridyl Chelate Ring Size on Catalyst Activity and Longevity

Abstract

Expansion of the dipyridyl ligand from a five- to six-membered chelate for PtII-catalyzed ethylene hydrophenylation provides an enhancement of catalyst activity and longevity. Mechanistic studies of [(dpm)Pt(Ph)(THF)][BAr′4] [dpm = 2,2′-dipyridylmethane, and Ar′ = 3,5-(CF3)2C6H3] attribute the improved catalytic performance at elevated temperatures to a favorable change in entropy of activation with an increase in chelate ring size. The PtII catalyst precursor [(dpm)Pt(Ph)(THF)][BAr′4] is among the most active catalysts for ethylene hydrophenylation by a non-acid-catalyzed mechanism.