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 towards 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 has thus far always resulted in formation of multinuclear 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 a Si(II)- source to iron(II), followed by a two-step reduction. The DFT structure of the resulting η2-disilylene-iron complex reveals metal-to-silicon -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 azide adduct and the 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.