Probing the origin of ambiphilic reactivity in osmapentalyne complexes: Interplay of ring strain, aromaticity, and phosphonium substituent.

• The methods of NPA, LOL, ACID, CDD were examined to probe the origin of the chameleonic reactivity on the carbyne carbon atoms. • The thermodynamics and kinetics of the nucleophilic reactivity of cyclic conjugated complexes were investigated by DFT calculations. • The ring strain, aromaticity, and the phosphonium substituent determine the ambiphilicity of the same carbyne carbon. 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 attentions have 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. A series of osmium carbyne complexes ranging from acyclic to cyclic, non-conjugated to conjugated, non-aromatic to aromatic, unsubstituted to substituted were designed for comparable studies. Our results indicate that the origin of ambiphilic reactivity in osmapentalyne complexes should be attributed to an interplay of ring strain, aromaticity, and phosphonium substituent. [Display omitted] [ABSTRACT FROM AUTHOR]