Monosubstituted Doublet Sn(I) Radical Featuring Substantial Unquenched Orbital Angular Momentum

Due to their intrinsic high reactivity, isolation of heavier analogues of carbynes remains a great challenge. Here, we report the synthesis and characterization of a neutral monosubstituted Sn(I) radical () supported by a sterically hindered hydrindacene ligand, which represents the first tin analogue of a free carbyne. Different from all Sn(I/III) species reported thus far, the presence of a sole Sn-C σ bond in renders the remaining two Sn 5p orbitals energetically almost degenerate, of which one is singly occupied and the other is empty. Consequently, its = 1/2 ground state possesses two-fold orbital pseudo-degeneracy and substantial unquenched orbital angular momentum, as evidenced by one component of its matrix (1.957, 1.896, and 1.578) being considerably less than 2. Consistent with this unique electronic structure, can bind to an -heterocyclic carbene to afford a neutral two-coordinate Sn(I) radical and initiate a one-electron transfer to benzophenone to furnish a Sn(II)-ketyl radical anion adduct. As a manifestation of its Sn-centered radical nature, reacts with diphenyl diselenide and -benzoquinone to form Sn-S and Sn-O bonds, respectively.