Cyclic diboranes(4) based on a chelating monoanionic benzylphosphine linker were prepared through boron-silicon exchange between arylsilanes and B Br . Coordination of Lewis bases to the remaining sp boron atom yielded unsymmetrical sp -sp diboranes, which were reduced with KC to their corresponding trans-diborenes. These compounds were studied with a combination of spectroscopic methods, X-ray diffraction, and DFT calculations. PMe -stabilized diborene 6 was found to undergo thermal rearrangement to gem-diborene 8. DFT calculations on 8 reveal a polar boron-boron bond, and indicate that the compound is best described as a borylborylene.

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Cyclic diboranes(4) based on a chelating monoanionic benzylphosphine linker were prepared by boron-silicon exchange between arylsilanes and B2Br4. Coordination of Lewis bases to the remaining sp 2 boron atom yielded unsymmetrical sp 3 -sp 3 diboranes, which were reduced with KC8 to their corresponding trans-diborenes. These compounds were studied by a combination of spectroscopic methods, X-ray diffraction and DFT calculations. PMe3-stabilized diborene 6 was found to undergo thermal rearrangement to gemdiborene 8. DFT calculations on 8 reveal a polar boron-boron bond, and indicate that the compound is best described as a borylborylene.