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.     

Kinetic Destabilization of Metal–Metal Single Bonds: Isolation of a Pentacoordinate Manganese(0) Monoradical

The 17e⁻ monoradical [Mn(CO)₅] is widely recognized as an unstable organometallic transient and is known to dimerize rapidly with the formation of a Mn Mn single bond. As a result of this instability, isolable analogues of [Mn(CO)₅] have remained elusive. Herein, we show that two sterically encumbering isocyanide ligands can destabilize the Mn Mn bond leading to the formation of the isolable, manganese(0) monoradical [Mn(CO)₃(CNAr^Dipp2)₂] (Ar^Dipp2=2,6‐(2,6‐(iPr)₂C₆H₃)₂C₆H₃). The persistence of [Mn(CO)₃(CNAr^Dipp2)₂] has allowed for new insights into nitrosoarene spin‐trapping studies of [Mn(CO)₅].     

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.