PREPARATION, CHARACTERIZATION, AND REACTION OF NOVEL DIOXORUTHENIUM(VI) PORPHYRIN CATION RADICAL COMPLEXES

Novel dioxoruthenium (VI) porphyrin cation radicals were prepared in the stoichiometric oxidation of Ru(VI)TMP-(O)2 (1) and Ru(VI)OEP(O)2 (2) with phenoxathiin hexachloroantimonate. H-2-NMR,UV-vis,and ESR were measured to determine the electronic structure of the oxidation products. The oxidation product (3) of 1 shows a broad Q band and a less intense and blue-shifted Soret band, suggestive of the porphyrin cation radical formation. Further, the single ESR signal for 3 at g = 2.002 at 77 K is a clear demonstration of one-electron oxidation of the porphyrin ring to form a free radical complex. The presence of two oxo ligands in 3 was confirmed in the reaction of 3 with Ph3P under argon to give 2 mol equiv of Ph3P=O. Very similar results were also obtained when 2 was oxidized under the same condition, and the oxidation product (4) was also assigned to be a dioxoruthenium(VI) porphyrin cation radical. The chemical shifts of 3 and 4 were determined by deuterium NMR using partially deuterated 3 and 4. On the basis of paramagnetic shifts, the radical orbitals of 3 and 4 were determined to be A1u. Further, oxidation reactions of diphenyl sulfide and some olefins were carried out with high valent ruthenium complexes (1-4), and the results show that 3 and 4 exhibit greater reactivity than 1 and 2; however, the enhancement of the reactivities arc less than those expected for the complexes bearing A2u radical orbitals.