Abstract: The experiments that the reductive deuteration and products-selectivity of C₂H₂ are affected by N₂ in D₂O-nitgrogenase have been done.It is found that the C₂H₂ reductive activities decreased ca.80.7% and 89.3%,respectively,with mixtures of C₂H₂and N₂ in the ratios of 1;108.3 and 1;216.7(volume ratio),as compared with ca.42.6% and 74.2% observed with C₂H₂ in argon(1;65 and 1;108.3,volume ratio) in the absence of N₂;ca.3.19% and 4.95% trans-2-didutero ethene were observed form FTIRspectra of the ethenes-1,2-d₂ obtained, respectively,with mixtures of C₂H₂ and N₂ in the ratios of1;108.3 and 1;216.7(volume ratio).The results give a strong proof for the conclusion in which N₂ binds inside the cage of M-cluster.

Key words: N₂-bonding site, M-cluster, C₂H₂ reductive activity, Stereo-selectivity