Photo-disproportionation of a bis-porphyrin-diruthenium(IV)-�-oxo dimer gave a porphyrin-ruthenium(III) species and a putative poprhyrin-ruthenium(V)-oxo species that can be detected and studied in real time via laser flash photolysis methods. As determined by its spectral and kinetic behavior, the same oxo transient was also formed by photolysis of a porphyrin-ruthenium(III) N-oxide adduct. Second-order rate constants for reactions with several substrates at 22 �C were determined; representative values of rate constants were kox= 6.6 � 103 M-1 s-1 for diphenylmethanol,  kox= 2.5 � 103 M-1 s-1 for styrene, and kox= 1.8 � 103 M-1 s-1 for cyclohexene. The putative porphyrin-ruthenium(V)-oxo transient reacted 5-6 orders of magnitude faster than the corresponding trans-dioxoruthenium(VI)-oxo porphyrins, and the rate constants obtained in this work were similar to those of corrole-iron(V)-oxo derivative. In this presentation, we will also demonstrate that photo-disproportionation reactions appear to be a promising way to produce such highly reactive ruthenium(V)-oxo intermediates in a recycling base for useful oxidative catalysis.

Photochemical generation of a highly reactive porphyrin-ruthenium(V)-oxo species for the selective oxidative catalysis

248th National Meeting (2014)

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