From Classical to Nonclassical Metal-Boron Bonds: Synthesis of a Novel Metallaborane

Boron, butterflies, and the missing link: The first synthetic link between electron-precise borylene complexes such as 1 and electron-deficient metallaboranes is achieved with the preparation of 2. This result introduces two novel features to the chemistry of the metallaboranes—unbridged B2Hal2 moieties (Hal=halogen) as cluster fragments and the four vertex nido-“butterfly” as a structural motif.