A singly bonded gallanediyl with redox-active and redox-inert reactivity

Abstract

Singly bonded metallylenes (R–M:) of the group 13 elements feature a non-bonding pair of electrons together with two vacant orbitals, which makes them highly reactive ambiphiles that readily activate small molecules by oxidative addition. As a consequence of their pronounced reactivity, examples of organometallics with singly bonded aluminium(I) and gallium(I) centres remain rare. Here we report the one-step synthesis of a monomeric gallium(I) compound that readily undergoes oxidative addition reactions and, more remarkably, carbometalation reactions with alkynes by retention of the low +I oxidation state and the singly bonded nature of gallium. This observation contrasts with common reports on the reactivity of low-valent main-group compounds, which are regularly oxidized to compounds in a more stable higher oxidation state. This approach provides access to low-valent main-group compounds and paves the way for the development of bond-functionalization strategies that may enable the discovery of catalytic processes in the future. A singly bonded gallanediyl undergoes carbometalation reactions with alkynes by retaining the low +I oxidation state and the singly bonded nature of gallium. The insertion into the gallium(I)–carbon bond proceeds regioselectively and gives exclusively the syn-addition products.