Probing the Origin of Ambiphilic Reactivity in Osmapentalyne Complexes: Interplay of Ring Strain, Aromaticity, and Phosphonium Substituent

Ambiphilic reactivity is a fascinating topic in chemical reactions, attracting considerable interest because ambiphilic reagents can display properties of both nucleophilicity and electrophilicity. However, most of the previous attention has been focused on the characterization of the ambiphilic reactivity, whereas the origin is less understood. Here we carry out thorough density functional theory (DFT) calculations to probe the origin of the ambiphilic reactivity of the carbyne atom in osmapentalynes, observed previously in experiment.

Stabilization of anti-aromatic and strained five-membered rings with a transition metal

Anti-aromatic compounds, as well as small cyclic alkynes or carbynes, are particularly challenging synthetic goals. The combination of their destabilizing features hinders attempts to prepare molecules such as pentalyne, an 8π-electron anti-aromatic bicycle with extremely high ring strain. Here we describe the facile synthesis of osmapentalyne derivatives that are thermally viable, despite containing the smallest angles observed so far at a carbyne carbon.