Computational study of methane C-H activation by first-row late transition metal L(n)M=E (M: Fe, Co, Ni) complexes.
Methane functionalization via L(n)M=E active species (L(n) = beta-diketiminate, dihydrophosphinoethane; M = Fe-Ni, E = NCF(3), NCH(3), O) through a hydrogen atom abstraction (HAA)/radical rebound (RR) mechanism is calculated to be thermodynamically and kinetically feasible. The enthalpies of each reaction decrease in the order Fe > Co > Ni and with the proximity of CF(3) supporting ligand substituents ("fluorination") to the metal center. For HAA, lower abstraction enthalpies were calculated for L(n) = beta-diketiminate and E = NCF(3) rather than dhpe and NCH(3), respectively, whereas the opposite trend was found for RR enthalpies. The overall functionalization thermodynamics were optimal for L(n) = beta-diketiminate and E = NCH(3), with similar enthalpies for E = O when M = Ni. The HAA kinetics further implicate fluorinated (beta-diket)Ni=O as the most promising methane functionalization complexes, with calculated activation barriers as low as 8.1 kcal mol(-1).
Pierpont
Aaron W
AW
Department of Chemistry and Center for Advanced Scientific Computing and Modeling, University of North Texas, P.O. Box 305070, Denton, Texas 76203-5070, USA.
Cundari
Thomas R
TR