Ambient Temperature Isolation of a Monatomic Boron(0) Complex

The first bottleable example of a neutral Group 13 atom bound only by neutral donor ligands (L) has been fully characterized by spectroscopic methods and its structure determined by a single-crystal X-ray diffraction study. A two-coordinate paramagnetic L₂B⁰ complex can readily be accessed through a facile reduction reaction and is stabilized by π-accepting cyclic (alkyl)(amino)carbene (CAAC) ligands. Further reduction of (CAAC)₂B leads to the isolation of a stable diamagnetic boride anion. In turn, oxidation leads to the putative formation of a transient two-coordinate cationic borylene, which has been trapped to form a stable boron(I) complex. Density functional theory calculations support the formulation of (CAAC)₂B as a boron(0) complex stabilized by strong multiple bonding.