Organo-rhodium and -iridium complexes containing the thiosulfate (S2O32−) ligand

Abstract

Reaction of the complexes [M2(μ-Cl)2(cod)2] (M = Rh, Ir) with sodium thiosulfate pentahydrate gives the dinuclear thiosulfate complexes [M2(μ-S2O3)2(cod)2]2−, which were isolated as their Ph3PCH2Ph+ salts. An X-ray structure determination on the Rh complex confirms the dimeric nature of the complex, with the two Rh(I) centres bridged by the terminal sulfurs of the thiosulfate ligands. Using ESI mass spectrometry, the dimer [M2(μ-S2O3)2(cod)2]2− and monomer [M(S2O3)(cod)]− are both observed, depending on the metal and capillary exit voltage. Reaction of sodium thiosulfate pentahydrate with the complexes trans-[RhCl(CX)(PPh3)2] (X = O or S) gave the anionic complexes Na[Rh(S2O3)(CX)(PPh3)], which were characterised by 31P{1H} NMR and IR spectroscopies, ESI MS, and in the case of the thiocarbonyl complex, by elemental analysis. Pentamethylcyclopentadienyl (Cp*) rhodium(III) and iridium(III) thiosulfate complexes [(Cp*M)2(μ -S2O3)3]2− were also synthesised by reaction of the chloride-bridged dimers [Cp*MCl2]2 with sodium thiosulfate, and isolated as their Ph3PCH2Ph+ salts. The complexes gave the expected parent dianions in ESI mass spectra, which underwent fragmentation of a thiosulfate ligand at higher capillary exit voltages to give ions [(Cp*M)2(S2O3)2S + H]−.