Abstract:Recently, homogeneous cobalt systems were reported to catalyze the reductive silylation of dinitrogen. In this study the investigations on the silylation of dinitrogen catalyzed by CoH(PPh 3 ) 3 N 2 are presented. We show that in the presence of the title compound, the reaction of N 2 with trimethylsilylchloride and sodium yields, on average, 6.7 equivalents of tris(trimethylsilyl)amine per Co atom in THF (tetrahydrofuran). The aim was to elucidate whether the active catalyst is: (a) the [Co(PPh 3 ) 3 N 2 ]´anion formed after two-electron reduction of the title compound; or (b) a species formed via decomposition of CoH(PPh 3 ) 3 N 2 in the presence of the highly reactive substrates. Time profile, and IR and EPR spectroscopic investigations show instability of the pre-catalyst under the applied conditions which suggests that the catalytically active species is formed through in situ modification of the pre-catalyst.