An Ir-catalyst featuring a PCP ligand based on an N-heterocyclic olefin triggers excellent activities in the solventless dehydrogenation of formic acid.

The mononuclear square-planar Rh{κ²-X,N-(Xpy)}(η²-coe)(IPr) (X = O, NH, NMe, S) complexes have been synthesized from the dinuclear precursor [Rh(μ-Cl)(IPr)(η²-coe)]₂ and the corresponding 2-heteroatom-pyridinate salts. The Rh-NHC-pyridinato derivatives are highly efficient catalysts for gem-specific alkyne dimerization. Particularly, the chelating N,O-pyridonato complex displays turnover frequency levels of up 17 000 h^–1 at room temperature. Mechanistic investigations and density functional theory calculations suggest a pyridonato-based metal–ligand cooperative proton transfer as responsible for the enhancement of catalytic activity. The initial deprotonation of a Rh-π-alkyne complex by the oxo-functionality of a κ¹-N-pyridonato moiety has been established to be the rate-limiting step, whereas the preferential protonation of the terminal position of a π-coordinated alkyne accounts for the exclusive observation of head-to-tail enynes. The catalytic cycle is closed by a very fast alkenyl–alkynyl reductive elimination.

Ir-NSi-based catalysts allow controlling the selective reduction of CO₂ with HSiMe(OSiMe₃)₂ to afford methoxysilane or silyl formate.