Electronic structures of different d configurations have been studied in relation to the facility of protonation to dinitrogen ligand in Cr(0) and Co(I) complexes. The d6 Cr complex has much better MO's for protonation than the d8 Co complex. This difference largely affects the protonation energies and the reduction of nitrogen molecule in these complexes.
Push–Pull Activation of N
2
: Coordination of Lewis Acids to Dinitrogen Complexes