Mechanistic investigation of the oxidative addition reactions between different iridium (I) cyclooctadiene ([Ir(LL ')(cod)]) complexes and iodomethane

摘要

The oxidative addition reactions between two different [Ir(cod)(LL ')] complexes (LL ' = hpt and AnMetha) and iodomethane was kinetically investigated. The rate of oxidative addition was determined as 2.2(2) x 10(-2) and 2.69(6) x 10(-2) M-1 s(-1) for [lr(cod)(hpt)] and [Ir(cod)(AnMetha)] in nitromethane respectively. The large negative entropy of activation for the above-mentioned reactions in different solvents clearly point to an associative mechanism. An intrinsic volume of activation of -30.5(3) and -28(3) cm(3) mol(-1) was determined for [lr(cod)(hpt)] and [lr(cod)(AnMetha)], respectively. A linear transition state with large charge separation and central ion contraction due to oxidation, contributes to the negative volume of activation. (c) 2005 Elsevier B.V. All rights reserved.