Rhodium(iii) complexes with thiolate and thioether ligands derived from fac(S)-[Rh(aet)3] (aet = 2-aminoethanethiolate): selective formation, characterization and properties

Abstract

Alkylation of fac(S)-[Rh(aet)₃] (aet = NH₂CH₂CH₂S⁻) with use of 1,2-dibromoethane in N,N-dimethylformamide produces fac(S)-[Rh(aet)(baete)]²⁺ ([1]²⁺, baete = (NH₂CH₂CH₂SCH₂)₂), in which two of the three thiolato S atoms in fac(S)-[Rh(aet)₃] are linked by an ethylene group. When methyl iodide is used as an alkylating reagent, two of the three thiolato S atoms are methylated to give fac(S)-[Rh(aet)(mtea)₂]²⁺ ([2]²⁺, mtea = NH₂CH₂CH₂SCH₃). Complexes [1]²⁺ and [2]²⁺ were optically resolved into the two enantiomers by SP-Sephadex C-25 column chromatography. The synthesis of a trimethylated complex, fac(S)-[Rh(mtea)₃]³⁺ ([3]³⁺), has been achieved by treatment of an aqueous solution of [2]²⁺ with dimethyl sulfate. Reactions of [1]²⁺ or [2]²⁺ with Ag⁺ in a 2 ∶ 1 molar ratio in water produce S-bridged Rh^IIIAg^IRh^III trinuclear complexes, [Ag{Rh(aet)(baete)}₂]⁵⁺ ([4]⁵⁺) and [Ag{Rh(aet)(mtea)₂}₂]⁵⁺ ([5]⁵⁺), indicating that [1]²⁺ and [2]²⁺ act as an S-donating monodentate complex-ligand. These complexes have been characterized by UV-VIS absorption, CD and NMR spectroscopic methods, together with single-crystal X-ray analyses for [1]²⁺ and [3]³⁺.