Reaction of a Molybdenum Bis(dinitrogen) Complex with Carbon Dioxide: A Combined Experimental and Computational...

Refluxing Mo(CO)₆ in the presence of the phosphine-functionalized α-diimine ligand ^Ph2PPrDI allowed for substitution and formation of the dicarbonyl complex, (^Ph2PPrDI)Mo(CO)₂. Oxidation with I₂ followed by heating resulted in further CO dissociation and isolation of the corresponding diiodide complex, (^Ph2PPrDI)MoI₂. Reduction of this complex under a N₂ atmosphere afforded the corresponding bis(dinitrogen) complex, (^Ph2PPrDI)Mo(N₂)₂. The solid-state structures of all three compounds were found to feature a tetradentate chelate and cis-monodentate ligands. Notably, the addition of CO₂ to (^Ph2PPrDI)Mo(N₂)₂ is proposed to result in head-to-tail CO₂ coupling to generate the corresponding metallacycle and ultimately a mixture of (^Ph2PPrDI)Mo(CO)₂ and the bis(oxo) dimer, [(κ³-^Ph2PPrDI)Mo(O)(μ-O)]₂. Computational studies have been performed to gain insight into the reaction and evaluate the importance of cis-coordination sites for selective head-to-tail CO₂ reductive coupling, CO deinsertion, disproportionation, and stepwise CO₂ deinsertion.