Ruthenium Complexes of Thiaporphyrin and Dithiaporphyrin

Successful synthesis and characterization of the six-coordinated
complex [Ru­(STTP)­(CO)­Cl] (1; STTP = 5,10,15,20-tetratolyl-21-thiaporphyrinato)
allowed the development of the coordination chemistry of ruthenium–thiaporphyrin
through dechlorination and metathesis reactions. Accordingly, [RuII(STTP)­(CO)­X] (X = NO3– (2), NO2– (3), and N3– (4)) was synthesized and analyzed by single-crystal
X-ray structural determination and NMR, UV–vis, and FT-IR spectroscopic
methods. An independent reaction of STPPH and [Ru­(COD)­Cl2] led to [RuIII(STTP)­Cl2] (5),
which possessed a higher-valent Ru­(III) center and exhibited good
stability in the solution state. This stability allowed reversible
redox processes in a cyclic voltammetric study. Reactions of [Ru­(S2TTP)­Cl2] (S2TTP = 5,10,15,20-tetratolyl-21,23-dithiaporphyrinato)
with AgNO3 and NaSePh, also via the metathesis strategy,
resulted in novel dithiaporphyrin complexes [RuII(S2TTP)­(NO3)2] (6) and [Ru0(S2TTP)­(PhSeCH2SePh)2] (7), respectively. The structures of 6 and 7 were corroborated by X-ray crystallographic analyses. Complex 7 is an unprecedented ruthenium(0)–dithiaporphyrin
with two bis(phenylseleno)­methanes as axial ligands.
A comparison of the analyses of the crude products from reactions
of NaSePh and CH2Cl2 with or without [Ru­(S2TTP)­Cl2], further supported by UV–vis spectral
changes under stoichiometric reactions between [Ru­(S2TTP)­Cl2] and NaSePh, suggested a reaction sequence in the order of
(1) formation of a putative [RuII(S2TTP)­(SePh)2] intermediate, followed by (2) the concerted formation of
PhSe–CH2Cl and simultaneously a reduction of Ru­(II)
to Ru(0) and finally (3) nucleophilic substitution of PhSeCH2Cl by excess PhSe–, resulting in PhSeCH2SePh, which readily coordinated to the Ru(0) and completed the formation
of bis(phenylseleno)­methane complex 7.