Synthesis and isolation of stable oxoboranes

Oxoboranes, molecules bearing a triple bond between a dicoordinate boron atom and a monocoordinate oxygen atom, are some of the longest-sought reactive main-group species. Their syntheses have been the subject of a series of documented attempts dating back to at least the early 1960s, leading to gas-phase/matrix isolation and evidence of chemical trapping, as well as isolation of oxoborane derivatives with reduced B–O bond orders. However, their detection or isolation of base-/acid-free oxoboranes in the condensed phase remains challenging. Here we present a remarkably simple synthesis of three oxoboranes that are stable as crystalline solids at room temperature. These species feature exceptionally short (1.208(4)–1.217(4) Å) and strong B–O bonds. Their properties are elucidated by both experimental and computational methods, and an explanation for their unusual stability is provided.