A Phosphine-Coordinated Boron-Centered Gomberg-Type Radical

The P-coordinated boryl radical [Ph2P(naphthyl)BMes](.) (Mes=mesityl) was prepared by (electro)chemical reduction of the corresponding borenium salt or bromoborane. Electron paramagnetic resonance (EPR) analysis in solution and DFT calculations indicate large spin density on boron (60-70%) and strong P-B interactions (PB sigma donation and BP negative hyperconjugation). The radical is persistent in solution and participates in a Gomberg-type dimerization process. The associated quinoid-type dimer has been characterized by single-crystal X-ray diffraction.