Work

Unraveling Terminal Cobalt–Antimony Double Bond: Breaking New Ground in Heavy Pnictogen Multiple Bonds

Year: 2026

Type: article

Abstract: Terminal pnictinidene complexes featuring heavy group 15 elements (Sb, Bi) doubly bonded to transition metals remain exceptionally elusive compared to their lighter congeners. Herein, we demonstrate that N-heterocyclic carbenes (NHCs) can effectively cleave the Sb═Sb double bond of distibenes to yield monomeric, zwitterionic stibinide species. Subsequent transfer of the antimony moiety to a cobalt center generates a terminal cobalt-stibinidene complex. Structural analysis reveals a very short Co─Sb bond distance, which is corroborated by Wiberg and Mayer bond indices as well as frontier molecular orbital and natural bond orbital analyses, providing compelling evidence for an unprecedented covalent Co═Sb double bond. In addition, we demonstrate that this compound reacts with an alkyne in a (2π+2π) cycloaddition and with phenyl azide to form a three-membered ring, providing initial insight into its reactivity and drawing parallels with reactivity patterns established for lighter phosphinidene analogs. This work establishes a rational route to stabilize heavy-element multiple bonds via a controlled and operationally-simple distibene cleavage.

Source: Angewandte Chemie International Edition

DOI: 10.1002/anie.8012161