Dinitrogen silylation catalyzed by silylene cobalt(I) and silylene iron(I) chlorides.

In this contribution, Co(PMe 3 ) 3 Cl (1), bis(silylene) cobalt chlorides Co(LSi:) 2 (PMe 3 ) 2 Cl (LSi: = {PhC(N t Bu) 2 }SiCl (2); { p -CH 3 C 6 H 4 C(N t Bu) 2 }SiCl (3); and { p - t BuC 6 H 4 C(N t Bu) 2 }SiCl (4)) and bis(silylene) iron chlorides Fe(LSi:) 2 (PMe 3 ) 2 Cl (LSi: = {PhC(N t Bu) 2 }SiCl (5); { p -CH 3 C 6 H 4 C(N t Bu) 2 }SiCl (6); { p - t BuC 6 H 4 C(N t Bu) 2 }SiCl (7) and Fe(PMe 3 ) 2 Cl 2 (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(SiMe 3 ) 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.