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

Abstract

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 η 2 -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.

Reactions of main group compounds with azides forming organic nitrogen-containing species

“…In the case of the reaction of metalla-disilirane Si29 with TMSN 3 reported in 2022 by Vlugt, Bruin and Krogman et al , the four-membered product Si29-P1 was formed after heating at 40 °C for 1 h via the insertion of terminal N atom into the Si–Si bond. 138 Further heating the benzene solution of Si29-P1 to 80 °C induced the release of N 2 leading to Si29-P2 in 50% yield. XRD analysis confirmed the planarity of the Si 2 FeN four-membered ring in Si29-P1 and Si29-P2 .…”

Preparation of a Compound with a SiII−SiIV−SiII Bonding Arrangement

“…[17] Consequently, chemistry of low-valent silicon makes considerable contributions to modern main-group chemistry. [18][19][20][21] Early examples of bis-silylene with a Si I À Si I bond were reported by us as well as by Krogman and co-workers [11,22] However, heterovalent SiÀ Si bonds are very scarce in the literature. For instance, Aldridge and co-workers have isolated an acyclic silylene, A which contains a Si II À Si IV bond with bond distance of 2.386(1) Å.…”