A reproducible synthesis of a competent epoxidation catalyst, [Ru-VI(TPP)(0)(2)] (TPP = tetraphenylporphyrin dianion), starting from [Ru-II(TPP)(CO)L] (L = none or CH3OH), is described. The molecular structure of the complex was determined by using ab initio X-ray powder diffraction (XRPD) methods, and its solution behavior was in detail investigated by NMR techniques such as PGSE (pulsed field gradient spin-echo) measurements. [Ru-IV(TPP)(OH)](2)O, a reported byproduct in the synthesis of [Ru-VI(TPP)(O)(2)], was synthesized in a pure form by oxidation of [Ru-II(TPP)(CO)L] or by a coproportionation reaction of [Ru-VI(TPP)(O)(2)] and [Ru-II(TPP)(CO)L], and its molecular structure was then determined by XRPD analysis. [Ru-VI(TPP)(O)(2)] can be reduced by dimethyl sulfoxide or by carbon monoxide to yield [Ru-II(TPP)(S-DMSO)(2)] or [Ru-II(TPP)(CO)(H2O)], respectively. These two species were characterized by conventional single-crystal X-ray diffraction analysis.