Four‐Membered Bimetallic Carbon Complex [(M(η5‐C5(CH3)5))2(μ‐NPh)(μ‐C)] (M=Fe, Ru, Os) – An Ambiphilic Carbene with Lone Pair and σ‐Hole Reactivity

Abstract

AbstractSinglet carbenes are extensively studied compounds capable of electrophilic, nucleophilic or ambiphilic behaviour. The ambiphilic reactivity of singlet carbenes has been conventionally observed in orthogonal planes. Here, we report a detailed bonding and reactivity study of a homobimetallic carbon complex [(MCp*)2(μ‐NPh)(μ‐C)] (1M, M=Fe, Ru, Os) that shows ambiphilicity in the same direction. The structure of this complex can be considered as two fused three‐membered M−C−M and M−N−M rings. The bonding analysis suggests that these 17 valence electron homobimetallic complexes have one formal M−M bond with a bridging carbene centre featuring a high‐lying spn‐hybridised lone pair. Accordingly, the carbene centre shows high proton affinity and act as a good 2e− donor to Lewis acids and transition metal fragment. Apart from the transition metal non‐bonding electrons, the π‐framework of M−C−M and M−N−M arms can be best described as 3c–2e− bonds. The two transition metals in the four‐membered skeleton generate many low‐lying, virtual orbitals. These low‐lying virtual orbitals induce electron excitation from the spn‐hybrid orbital in presence of H− and other 2e− donor ligands such as PMe3, NHC and CO. Hence, the spn‐hybrid lone pair orbital shows σ‐hole reactivity in presence of Lewis bases.