Halide-Dependent Mechanisms of Reductive Elimination from Gold(III)

[Image: see text] Two unique organometallic halide series (Ph(3)P)Au(4-Me-C(6)H(4))(CF(3))(X) and (Cy(3)P)Au(4-F-C(6)H(4))(CF(3))(X) (X = I, Br, Cl, F) have been synthesized. The PPh(3)-supported complexes can undergo both C(aryl)–X and C(aryl)–CF(3) reductive elimination. Mechanistic studies of thermolysis at 122 °C reveal a dramatic reactivity and kinetic selectivity dependence on halide ligand. For X = I or F, zero-order kinetic behavior is observed, while for X = Cl or Br, kinetic studies implicate product catalysis. The selectivity for C(aryl)–CF(3) bond formation increases in the order X = I < Br < Cl < F, with exclusively C(aryl)–I bond formation when X = I, and exclusively C(aryl)–CF(3) bond formation when X = F. Thermodynamic measurements show that Au(III)–X bond dissociation energies increase in the order X = I < Br < Cl, and that ground state Au(III)–X bond strength ultimately dictates selectivities for C(aryl)–X and C(aryl)–CF(3) reductive elimination.