Closed Synthetic Cycle for Nickel-Based Dihydrogen Formation.

Dihydrogen evolution was observed in a two-step protonation reaction starting from a Ni precursor with a tripodal N-heterocyclic carbene (NHC) ligand. Upon the first protonation, a Ni monohydride complex was formed, which was isolated and fully characterized. Subsequent protonation yields H via a transient intermediate (INT) and an isolable Ni acetonitrile complex.

(CAAC)Pd(py) Catalysts Disproportionate to Pd(CAAC).

Palladium complexes with one -heterocyclic carbene (NHC) and a pyridine ancillary ligand are powerful cross-coupling precatalysts. Herein, we report such complexes with a cyclic (alkyl)(amino)carbene (CAAC) ligand replacing the NHC. We find that the alleged reduced form, (CAAC)Pd(py), disproportionates to the (CAAC)Pd complex and palladium nanoparticles.