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

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) × 10−2 and 2.69(6) × 10−2 M−1 s−1 for [Ir(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) cm3 mol−1 was determined for [Ir(cod)(hpt)] and [Ir(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.