Preparation, characterization, and reaction of novel dioxoruthenium(VI) porphyrin cation radical complexes

Abstract

Novel dioxoruthenium(VI) porphyrin cation radicals were prepared in the stoichiometric oxidation of Ru[sup VI]TMP(O)[sub 2] (1) and Ru[sup VI]OEP(O)[sub 2] (2) with phenoxathiin hexachloroantimonate. [sup 2]H-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 Ph[sub 3]P under argon to give 2 mol equiv of Ph[sub 3]P[double bond]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) prophyrin 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 A[sub 1u]. Further, oxidation reactions of diphenyl sulfide and somemore » 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 are less than those expected for the complexes bearing A[sub 2u] radical orbitals. 27 refs., 5 figs., 2 tabs.« less