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].     

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.