Pt^II-Catalyzed Hydrophenylation of α-Olefins: Variation of Linear/Branched Products as a Function of Ligand Donor Ability

Abstract

The PtII complexes [(xbpy)Pt(Ph)(THF)]+ (xbpy = 4,4′-X2-2,2′-bipyridyl; x = OMe (1a), tBu (1b), H (1c), Br (1d), CO2Et (1e) and NO2 (1f)] catalyze the formation of n-propylbenzene and cumene from benzene and propene. The catalysts are selective for branched products, and the cumene/n-propylbenzene ratio decreases with increasing donor ability of the xbpy ligand. DFT(D) calculations predict more favorable activation barriers for 1,2-insertion into the Pt–Ph bond to give branched products. The calculations indicate that 1,2-insertion of propene should be faster than 2,1-insertion for all Pt(II) catalysts studied, but they also indicate that cumene/n-propylbenzene selectivity is under Curtin–Hammett control.