Front Cover: Mechanistic and Kinetic Investigations of ON/OFF (Photo)Switchable Binding of Carbon Monoxide by Chromium(0), Molybdenum(0) and Tungsten(0) Carbonyl Complexes with a Pyridyl‐Mesoionic Carbene Ligand (Chem. Eur. J. 51/2022)

Kinetic and mechanistic investigations of the photo‐induced reversible binding and release of CO to Cr0, Mo0 and W0 complexes with pyridyl‐mesoionic carbene ligands ([LM(CO)4]) are reported. Irradiation of the complexes in the solid state at 10 K leads to a FTIR spectroscopically detectable intermediate [LM(CO)3] without ligand–sphere reorganization. In solution, clean conversion to a stable photoproduct [LM(CO)3Xaxial] (X=MeCN, BuCN, Py) is observed. The photodissociation quantum yield increases from W0 via Mo0 to Cr0 up to 46 %. It is remarkable that there is a fully reversible CO exchange, especially as the reverse recombination reaction with the solvated CO can take hours (Cr≪Mo