Isolable cyclic radical cations of heavy main-group elements

One-electron oxidation of 1,3-digerma-2,4-dipnictacyclobutadiene [LHGeE]2 (LH = CH[CHNDipp]2, Dipp = 2,6-iPr2C6H3; 1: E = P; 2: E = As) with Ag[Al(ORF)4] (RF = C(CF3)3) afforded the stable radical cation salts 1•+•[Al(ORF)4]– and 2•+•[Al(ORF)4]–, respectively. The radical cation salts have been fully characterized, in conjunction with theoretical calculations. The EPR spectroscopic studies and DFT calculations reveal that the spin density mainly resides at the heavy pnictogen atoms, rather than delocalizes over the Ge2E2 ring. They represent the first structurally characterized cyclic radical species comprised of both heavy group 14 and 15 elements.