Stable Mixed-Valent Radicals from Platinum( II) Complexes of a Bis( dioxolene) Ligand

Three diplatinum(II) complexes [{PtL}(2)(-thea)] (H(4)thea=2,3,6,7-tetrahydroxy-9,10-dimethyl-9,10-dihydro-9,10-ethanoanthracene) have been prepared, with diphosphine or bipyridyl L co-ligands. One-electron oxidation of these complexes gave radical cations containing a mixed-valent [thea.](3-) ligand with discrete catecholate and semiquinonate centers separated by quaternary methylene spacers. The electronic character of these radicals is near the Robin-Day class II/III border determined by UV/Vis/NIR and EPR spectroscopies. Crystal-structure determinations and a DFT calculation imply that oxidation of the thea(4-) ligand may lead to an increased through-space interaction between the dioxolene systems.