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

Abstract

Refluxing Mo(CO) 6 in the presence of the phosphine-functionalized α-diimine ligand Ph2PPr DI allowed for substitution and formation of the dicarbonyl complex, ( Ph2PPr DI)-Mo(CO) 2 . Oxidation with I 2 followed by heating resulted in further CO dissociation and isolation of the corresponding diiodide complex, ( Ph2PPr DI)MoI 2 . Reduction of this complex under a N 2 atmosphere afforded the corresponding bis(dinitrogen) complex, ( Ph2PPr DI)Mo(N 2 ) 2 . The solid-state structures of all three compounds were found to feature a tetradentate chelate and cismonodentate ligands. Notably, the addition of CO 2 to ( Ph2PPr DI)Mo(N 2 ) 2 is proposed to result in head-to-tail CO 2 coupling to generate the corresponding metallacycle and ultimately a mixture of ( Ph2PPr DI)Mo(CO) 2 and the bis(oxo) dimer, [(κ 3 -Ph2PPr DI)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 CO 2 reductive coupling, CO deinsertion, disproportionation, and stepwise CO 2 deinsertion.