N2 Silylation Catalyzed by a Bis(silylene)-Based [SiCSi] Pincer Hydrido Iron(II) Dinitrogen Complex

The bis(silylene)-based SiC(sp(3))Si pincer ligand N,N'-bis(LSi:)dipyrromethane [SiCH2Si] (Ll; L = PhC(NtBu)(2)) with a C(sp(3)) atom anchor was synthesized, and its coordination chemistry to iron was studied. Two novel iron hydride complexes, [SiCHSi]Fe(H)(N-2)(PMe3) (1) and [SiCHSi]Fe(H)(PMe3)(2) (2), were synthesized in the reaction of L1 with Fe(PMe3)(4) via C(sp(3))-H bond activation under different inert atmospheres (N-2 and argon). To the best of our knowledge, 1 and 2 are the first examples of a bis(silylene)-based hydrido pincer iron complex produced through activation of a C(sp(3))-H bond. At the same time 1 is also the first example of a TM dinitrogen complex supported by a bis(silylene) ligand. The interconversion between 1 and 2 was achieved and monitored by operando IR and P-31 NMR spectra to understand the transformation from 1 to 2 from the viewpoint of kinetics. To our delight, 1 could effectively catalyze silylation of dinitrogen and gave the highest turnover number so far among all the Fe-catalyzed N-2 silylation systems at room temperature and under atmospheric dinitrogen.