Facile Deoxygenative Reduction of a Bridging Carbonato Ligand with Silyl and Boryl 4,4’-Bipyridinylidene Reagents

The reactivity of CO2 with a previously described PCcarbeneP cobalt(I) hydroxide is reported. Insertion of CO2 into the Co-OH bond followed by a dehydration reaction releasing water results in a cobalt(I) bridging carbonate species featuring fluctional κ1: κ1 and κ1: κ2 coordination of the central carbonate moiety. The reduction chemistry of the resulting cobalt(I) bridging carbonate species is explored utilizing deoxygenative reducing agents N,N′-bis(trimethylsilyl)- and N,N′-bis(pinacolatoboryl)-4,4′-bipyridinylidene. The three-electron reduction produces the corresponding PCcarbeneP cobalt(I) siloxide or boroxide complex alongside a PCcarbeneP cobalt(0) monocarbonyl, silyl/boryl ether, and 4,4’-bipyridine.