Biaryl Reductive Elimination Is Dramatically Accelerated by Remote Lewis Acid Binding to a 2,2′-Bipyrimidyl–Platinum Complex: Evidence for a Bidentate Ligand Dissociation Mechanism

Abstract

The silicon and zinc Lewis acids Si(cat)2 (cat = catecholato), Si(catF)2 (catF = tetrafluorocatecholato), and Zn(C6F5)2 bind to the remote ligand site of a 2,2′-bipyrimidyl–platinum diaryl complex. This platinum complex provides a platform to systematically evaluate electronic and reactivity differences triggered by Lewis acid binding. The electron density of the bipyrimidine ligand is substantially depleted upon Lewis acid binding, as evidenced by UV–vis spectroscopy and cyclic voltammetry. Biaryl reductive elimination studies allowed quantification of the effect of Lewis acid binding on reactivity, and Lewis acid binding accelerated reductive elimination rates by up to 8 orders of magnitude. Kinetics experiments in combination with DFT studies support an unusual mechanism featuring complete dissociation of the Lewis acid-coordinated bidentate bipyrimidine ligand prior to reductive elimination.