Binuclear Acetoniminato Derivatives of Iron and Chromium Carbonyls: A Theoretical Study

Abstract The structures and energetics of binuclear acetoniminato metal carbonyl derivatives of the types (Me2CN)2Fe2(CO)n and (Me2CN)2Cr2(CO)n have been investigated by density functional theory. The (Me2CN)2Fe2(CO)6 structure, with bridging Me2CN ligands using only their nitrogen atoms to bridge an FeFe bond related to experimentally known species, as well as a related (Me2CN)2Cr2(CO)8 structure, appear to be energetically preferred. Among carbonyl-richer systems, the iron system energetically prefers a {Me2CNC­(O)}2Fe2(CO)6 structure with bridging Me2CNC­(O) ligands, whereas the chromium system energetically prefers a structure with a 2,3-diazabutadiene ligand having each nitrogen atom bonded to a Cr­(CO)5 moiety. Preferred structures for systems with fewer CO groups include the tetracarbonyl (Me2CN)2Fe2(CO)4 in which one of the bridging Me2CN uses its CN double bond to bond to an iron atom, as well as (Me2CN)2Cr2(CO)n (n = 7, 6) structures with chromium–chromium multiple bonds bridged by Me2CN groups.