An Isolable One‐Coordinate Lead(I) Radical with Strong g‐Factor Anisotropy

Abstract

Lead‐based radicals in the oxidation state of +1 are elusive species and are highly challenging to isolate in the condensed phase. In this study, we present the synthesis and characterization of the first isolable free plumbylyne radical 2 bearing a one‐coordinate Pb(I) atom. It reacts with an N‐heterocyclic carbene (NHC) to afford a two‐coordinate NHC‐ligated Pb(I) radical 3. 2 and 3 represent the first isolable Pb(I)‐based radicals. Theoretical calculations and electron paramagnetic resonance analysis revealed that the unpaired electron mainly resides at the Pb 6p orbital in both radicals. Owing to the unique one‐coordinate nature of the Pb atom in 2, it possesses two‐fold orbital pseudo‐degeneracy and substantial unquenched orbital angular momentum, and exhibits hitherto strongest g‐factor anisotropy (gx,y,z = 1.496, 1.166, 0.683) amongst main group radicals. Preliminary investigations into the reactivity of 2 unveiled its Pb‐centered radical nature, and plumbylenes were isolated as products.