Solid/gas in crystallo reactivity of an Ir(I) methylidene complex

In crystallo stabilization of known, but solution unstable, methylidene complex [Ir(^tBu-PONOP)(═CH2)][BAr^F₄] allows single-crystal to single-crystal solid/gas reactivity associated with the {Ir═CH₂} group to be studied. Addition of H₂ results in [Ir(^tBu-PONOP)(H)₂][BAr^F₄]; exposure to CO forms iridium(I) carbonyl [Ir(^tBu-PONOP)(CO)][BAr^F₄], and reaction with NH₃ gas results in the formation of methylamine complex [(^tBu-PONOP)Ir(NH2Me)][BAr^F₄] via an aminocarbene intermediate. Periodic density functional theory and electronic structure analyses confirm the Ir═CH₂ bond character but with a very low barrier to rotation around the Ir═CH₂ bond. Calculations show that addition of NH₃ 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.