A radical mechanism for C-H bond cross-coupling and N2 activation catalysed by β-diketiminate iron complexes

Our density functional theory calculations reveal a radical mechanism for N-2 fixation and conversion to N(SiMe3)(3) and PhN(SiMe3)(2) catalysed by a diketiminate-supported iron system. We found that the Na(15-crown-5)* radical plays an essential role as a co-catalyst in the reaction for the formation of the Me 3 Sr radical and a stable intermediate. The attack of two Me3Si* radicals to distal nitrogen and the phenyl migration to proximal nitrogen gradually weaken and activate the N N bond. The turnover-limiting step in the whole catalytic reaction is the activation of the C-H bond with a free energy barrier of 20.3 kcal mor(-1). Molecular orbital analysis of dinitrogen complexes indicates that the pi back-bonding interactions between iron and N-2 orbitals have major contributions to N-2 fixation.