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

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.