Ruthenium Complexes of Thiaporphyrin and Dithiaporphyrin

Abstract

Successful synthesis and characterization of the six-coordinated complex [Ru­(STTP)­(CO)­Cl] (<b>1</b>; STTP = 5,10,15,20-tetratolyl-21-thiaporphyrinato) allowed the development of the coordination chemistry of ruthenium–thiaporphyrin through dechlorination and metathesis reactions. Accordingly, [Ru^II(STTP)­(CO)­X] (X = NO₃^<b>–</b> (<b>2</b>), NO₂^<b>–</b> (<b>3</b>), and N₃^<b>–</b> (<b>4</b>)) 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 [Ru^III(STTP)­Cl₂] (<b>5</b>), 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 [Ru^II(S₂TTP)­(NO₃)₂] (<b>6</b>) and [Ru⁰(S₂TTP)­(PhSeCH₂SePh)₂] (<b>7</b>), respectively. The structures of <b>6</b> and <b>7</b> were corroborated by X-ray crystallographic analyses. Complex <b>7</b> is an unprecedented ruthenium(0)–dithiaporphyrin with two <i>bis</i>(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 [Ru^II(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 <i>bis</i>(phenylseleno)­methane complex <b>7</b>