Theoretical study on electronic structure of (CNC)Fe-2N2 and its N2 elimination mechanism

Abstract

The density function theory (DFT) is to elucidate the electronic structure of bis(dinitrogen) Fe(0) complex, (CNC)Fe-2N2, and its N2 elimination mechanism. (CNC)Fe-2N2 has a low-spin singlet (S = 0) ground state with a distorted square pyramidal structure. Fragment orbital interaction analysis yields total occupancy of π* orbitals (LUF (4)O and LUF(4)O-1) of apical N3-N4 is 0.188 while that of basal N1-N2 is 0.187 in S0(CNC)Fe-2N2, suggesting nearly the same activation extent for both basal and apical N2 ligands. The lowest-lying triplet state T1 (3-A′) has a repulsive potential energy surface along the FeON3 bong length by PBE functional, while a minimum on T2 state (3-A″) with higher energy is found by B3LYP functional. The nonadiabatic N2 elimination mechanism of (CNC)Fe-2N2 involves an S0-T1 states crossing, which lowers the activation energy to 9.7 kcal/mol and produces high-spin intermediate (CNC)Fe-N2. © 2009 Wiley Periodicals, Inc.