Chemistry, Ames Laboratory
Journal or Book Title
Journal of Chemical Physics
To investigate the mechanism for N–H bond activation by a transition metal, the reactions of Co+(3F,5F) with NH3 have been studied with complete active space self-consistent field (CASSCF), multireference configuration interaction (MR-SDCI), and multireference many body perturbation theory (MRMP) wave functions, using both effective core potential and all-electron methods. Upon their initial approach, the reactants yield an ion–molecule complex, CoNH+3(3E,5A2,5A1), with retention of C3ν symmetry. The Co+=NH3 binding energies are estimated to be 49 (triplet) and 45 (quintet) kcal/mol. Subsequently, the N–H bond is activated, leading to an intermediate complex H–Co–NH+2 (C2ν symmetry), through a three-center transition state with an energy barrier of 56–60 (triplet) and 70–73 (quintet) kcal/mol. The energy of H–Co–NH+2, relative to that of CoNH+3, is estimated to be 60 to 61 (triplet) and 44 (quintet) kcal/mol. However, the highest levels of theory employed here (including dynamic correlation corrections) suggest that the triplet intermediate HCoNH+2 may not exist as a minimum on the potential energy surface. Following Co–N or H–Co bond cleavage, the complexH–Co–NH+2 leads to HCo++NH2 or H+CoNH+2. Both channels (triplet and quintet) are found to be endothermic by 54–64 kcal/mol.
Copyright 1997 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.
American Institute of Physics
Taketsugu, Tetsuya and Gordon, Mark S., "An Ab Initio Study of the Reaction Mechanism of Co++NH3" (1997). Chemistry Publications. 319.