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 (P→B σ donation and B→P 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.     

Isolation and Characterization of a Bismuth(II) Radical

More than 80 years after Paneth’s report of dimethyl bismuth, the first monomeric Bi^II radical that is stable in the solid state has been isolated and characterized. Reduction of the diamidobismuth(III) chloride Bi(NON^Ar)Cl (NON^Ar=[O(SiMe₂NAr)₂]²⁻; Ar=2,6‐iPr₂C₆H₃) with magnesium affords the Bi^II radical ^.Bi(NON^Ar). X‐ray crystallographic measurements are consistent with a two‐coordinate bismuth in the +2 oxidation state with no short intermolecular contacts, and solid‐state SQUID magnetic measurements indicate a paramagnetic compound with a single unpaired electron. EPR and density functional calculations show a metal‐centered radical with >90 % spin density in a p‐type orbital on bismuth.