Dinitrogen silylation catalyzed by silylene cobalt(i) and silylene iron(i) chlorides

Abstract

In this contribution, Co(PMe₃)₃Cl (1), bis(silylene) cobalt chlorides Co(LSi:)₂(PMe₃)₂Cl (LSi: = {PhC(N^tBu)₂}SiCl (2); {p-CH₃C₆H₄C(N^tBu)₂}SiCl (3); and {p-^tBuC₆H₄C(N^tBu)₂}SiCl (4)) and bis(silylene) iron chlorides Fe(LSi:)₂(PMe₃)₂Cl (LSi: = {PhC(N^tBu)₂}SiCl (5); {p-CH₃C₆H₄C(N^tBu)₂}SiCl (6); {p-^tBuC₆H₄C(N^tBu)₂}SiCl (7) and Fe(PMe₃)₂Cl₂ (8)) were synthesized to study the effects of different metals and silylene ligands on the catalytic activity of complexes 1–8 in dinitrogen silylation reaction. The experimental results indicate that there is no substantial difference in catalytic activity between the phosphine cobalt complex 1 and the silylene cobalt chlorides 2–4 although the cobalt silylene complex 2 has slightly better catalytic activity than complexes 1, 3 and 4 in the dinitrogen silylation. Silylene iron complexes 5–7 are more active than the phosphine iron complex 8. Among the three silylene iron(I) chlorides 5–7, complex 5 is the most effective catalyst for dinitrogen silylation and 402 equiv. of N(SiMe₃)₃ could be obtained per Fe atom. In the dinitrogen silylation reaction catalyzed by iron complexes, the introduction of the silylene ligand made the silylene iron complexes 5–7 more active than the phosphine iron complex 8. In addition, iron chlorides 5–8 are more effective catalysts than cobalt(I) chlorides 1–4 for the dinitrogen silylation reaction. Complexes 3, 4, 6 and 7 were new complexes, and their molecular structures were determined by single crystal X-ray diffraction analysis.