A kinetic investigation of the oxidative addition reactions of the dimeric Bu4N[Ir-2(mu-Dcbp)(cod)(2)] complex with iodomethane

摘要

The kinetic results of the oxidative addition of iodomethane to Bu4N[Ir-2(mu-Dcbp)(cod)(2)] (Dcbp = 3,5-dicarboxylatepyrazolate anion) show that oxidative addition can occur via a direct equilibrium pathway (K-1 = 88(22) acetone, 51(3) 1,2-dichloroethane, 55(4) dichloromethane, 52(12) acetonitrile and 43(5) M-1 chloroform) or a solvent-assisted pathway (k(2), k(3)). Oxidative addition occurs mainly along the direct pathway, which is a factor 10-40 faster than the solvent-assisted pathway. The observed solvent effect cannot be attributed to the donosity or polarity of the solvents. The fairly negative Delta S-not equal value (-110(7)J K-1 mol(-1)) and the positive Delta H-not equal value (+47(2) kJ mol(-1)) for the oxidative addition step are indicative of an associative process. (c) 2006 Elsevier B.V. All rights reserved.