Solid/Gas In Crystallo Reactivity of an Ir(I) Methylidene Complex

In crystallo stabilization of known, but solution unstable, methylidene complex [Ir( tBu-PONOP)(=CH 2)][BAr F 4] allows single-crystal to single-crystal solid/gas reactivity associated with the {Ir=CH 2} group to be studied. Addition of H 2 results in [Ir( tBu-PONOP)(H) 2][BAr F 4]; exposure to CO forms iridium(I) carbonyl [Ir( tBu-PONOP)(CO)][BAr F 4], and reaction with NH 3 gas results in the formation of methylamine complex [( tBu-PONOP)Ir(NH 2Me)][BAr F 4] via an aminocarbene intermediate. Periodic density functional theory and electronic structure analyses confirm the Ir=CH 2 bond character but with a very low barrier to rotation around the Ir=CH 2 bond. Calculations show that addition of NH 3 to the electrophilic alkylidene carbon gives an initial ammonium ylid intermediate. Stepwise N-H and C-H transfers then form the aminocarbene intermediate as a kinetic product from which two successive C-H couplings lead to the more stable methylamine product.