Winston Matthew S, Wolf William J, Toste F Dean
Department of Chemistry, University of California, Berkeley, California 94720, United States.
J Am Chem Soc. 2015 Jun 24;137(24):7921-8. doi: 10.1021/jacs.5b04613. Epub 2015 Jun 11.
Two unique organometallic halide series (Ph3P)Au(4-Me-C6H4)(CF3)(X) and (Cy3P)Au(4-F-C6H4)(CF3)(X) (X = I, Br, Cl, F) have been synthesized. The PPh3-supported complexes can undergo both C(aryl)-X and C(aryl)-CF3 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)-CF3 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)-CF3 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)-CF3 reductive elimination.
已经合成了两个独特的有机金属卤化物系列(Ph3P)Au(4-Me-C6H4)(CF3)(X) 和 (Cy3P)Au(4-F-C6H4)(CF3)(X)（X = I、Br、Cl、F）。由三苯基膦支撑的配合物可发生芳基-C-X和芳基-CF3还原消除反应。在122°C下热解的机理研究表明，反应活性和动力学选择性强烈依赖于卤化物配体。当X = I或F时，观察到零级动力学行为，而当X = Cl或Br时，动力学研究表明存在产物催化作用。芳基-CF3键形成的选择性按X = I < Br < Cl < F的顺序增加，当X = I时仅形成芳基-I键，而当X = F时仅形成芳基-CF3键。热力学测量表明，Au(III)-X键离解能按X = I < Br < Cl的顺序增加，并且基态Au(III)-X键强度最终决定了芳基-C-X和芳基-CF3还原消除反应的选择性。
