3-Center-5-Electron Boryl Radicals with σ0π1 Ground State Electronic Structure

Five- and six-membered boron heterocycle-based three-center-five-electron (3c-5e) type boryl radicals with unusual sigma(0)pi(1) ground state electronic structures are predicted theoretically. Compared to sigma(0)pi(1) analogs, their unique electronic structure leads to both lower reactivity toward Hatoms and stronger coordination with Lewis bases. The corresponding Lewis base-stabilized four-center-seven-electron (4c-7e) type boryl radicals are even more unreactive toward H-atoms than the conventional 4c-7e ones.