High-Pressure NMR Studies on the Alternating Copolymerization of Propene with Carbon Monoxide Catalyzed by a Palladium(II) Complex of an Unsymmetrical Phosphine−Phosphite Ligand

Abstract

When high-pressure NMR techniques are employed, the following two facts are revealed. (1) The cis/trans isomerization from (SP-4-4)-[Pt(CH3)(CO)(L1)][BAr4] (8a; L1 = (R,S)-BINAPHOS; Ar = 3,5-(CF3)2C6H3) to the more stable SP-4-3 isomer (8b) is faster than CO insertion into either 8a or 8b, the CO insertion being reversible. (2) For the PdII−L1-catalyzed copolymerization of propene and CO, there exist at least two major resting states, most probably acylpalladium, (SP-4-3)-[Pd(COR)(L2)(L1)][BAr4] (3; L2 = CH3CN, CO), and alkylpalladium, [Pd{CH2CH(CH3)C(O)R}(L1)][BAr4] (5a).