Metalized Borylene in Boron‐Gold Carbonyl Complexes: Infrared Spectra and Theoretical Calculations

Abstract

Borylenes (:B–R), built on a single B–R bond between boron and another nonmetallic atom or group, are a heated subject of special interest due to their intriguing transition‐metal‐mimicking reactivity, but the relative lack of understanding for the electronic structure and chemical bonding of transition metal borides leads to lingering neglect of metalized borylenes (:B–M) based on covalent B–M bonding. Here we use infrared photodissociation spectroscopy in combination with density functional calculations to study the geometric structure and chemical bonding of boron‐gold carbonyl complex cations. The structure and bonding analyses demonstrated that the BAu(CO)3+ and BAu2(CO)4+ complexes can be described as bis‐carbonyl‐trapped borylene adducts. While the metal‐rich BAu3(CO)4+ complex represents an unusual multicenter‐bond‐stabilized borylene cation with excellent σ‐acidity and π‐backbonding capability for CO activation, featuring Cs symmetry with a quasi‐T‐shaped BAu3+ core. It is manifested that BAu3+ presents greater amphoteric reactivity and improved stability compared to BAu1,2+ due to the presence of the three‐center‐two‐electron Au–B–Au bond. This study discloses a conceptually new platform for accessing reactive metalized borylenes by exploiting the boron‐mediated multicenter‐bond stabilization strategy and using more bench‐stable and ubiquitous metal carbonyl fragments as starting materials, thus providing a broader opportunity for the design of novel chemical structures and catalysts.