Reactivity of a Unique Si(I)–Si(I)-Based η²‑Bis(silylene) Iron Complex

In this paper, we report the synthesis of a unique silicon­(I)-based metalla-disilirane and report on its reactivity toward TMS-azide and benzophenone. Metal complexes containing disilylenes ((bis)­silylenes with a Si–Si bond) are known, but direct ligation of the Si­(I) centers to transition metals always generated dinuclear species. To overcome this problem, we targeted the formation of a mononuclear iron(0)–silicon­(I)-based disilylene complex via templated synthesis, starting with ligation of two Si­(II) centers to iron­(II), followed by a two-step reduction. The DFT structure of the resulting η2-disilylene-iron complex reveals metal-to-silicon π-back donation and a delocalized three-center–two-electron (3c–2e) aromatic system. The Si­(I)–Si­(I) bond displays unusual but well-defined reactivity. With TMS-azide, both the initial azide adduct and the follow-up four-membered nitrene complex could be isolated. Reaction with benzophenone led to selective 1,4-addition into the Si–Si bond. This work reveals that selective reactions of Si­(I)–Si­(I) bonds are made possible by metal ligation.