The coordination activation effects of Red Roussinate, MoFeS4(NO)22-, Black Roussinate, and the string bag model for the nitrogenase substrates (C2H2, N2, NNH+, and NCH) were simulated quantum chem. using EHMO calcns. Considering synthetically the variance of the total energy of the systems and the Muelliken bond orders of the multibonds of substrates, the optimal activation conformations for the system formed from dinuclear clusters and C2H2 is d = 1.2 ? where d is the distance between the CYC bond and MS2M' plane where M is metal atom); for the system formed from Black Roussinate and C2H2 in the cannon mount mode, q = 140? where q is the M-C1-C2 angle. Fe is more favorable than Mo for weakening the CYC bond. In the system formed from the string bag model and N2, NNH+, or NCH in diving mode, the multibond of substrates weakened greatly. In the diving mode the electronic d. of the N atom being out of the mouth of the bag is increased, thus favoring the attack of electrophile. The attack of H+ along the orientation of the N-N axis on the N2 is more advantageous for activating the NYN bond.

Key words: CATALYST, ACETYLENE, QUANTUM CHEMISTRY, REDUCTION, IRON COMPLEX, NITROGENASE, MOLYBDENUM COMPLEX, CHEMICAL BONDS, CLUSTER COMPOUND, MOLECULAR ORBITAL THEORY