E.S.R. spectra of diboranyl radicals in the solid states

E.S.R. Spectra of the radicals produced from the γ-irradiated diborane (6) in polycrystal or single crystal have been investigated. From the analysis of the results of the single crystal, the radical was identified as neutral diboranyl, ·B₂H₅, produced by extracting one of the two bridging hydrogen atoms of diborane. The major portion of the spin density on the radical is equally shared by the two boron atoms, a considerable portion exists on the bridging hydrogen atom, and a small portion with negative sign on the four terminal hydrogens. The orbitals of the unpaired electron on the two borons are in the same plane at an angle of 73°. These results are in good agreement with those from INDO calculation for the radicals. The structure of the radical is discussed in comparison with some other radicals having a similar structure.