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^F ₄] 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^F ₄]; exposure to CO forms iridium(I) carbonyl [Ir(^tBu-PONOP)(CO)][BAr^F ₄], and reaction with NH₃ gas results in the formation of methylamine complex [(^tBu-PONOP)Ir(NH₂Me)][BAr^F ₄] 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.