Transition Metal Complexes with Sulfur Ligands, Part 119. Synthesis of Water Soluble Fe and Ru Complexes with Novel Multidentate Thioether Thiolate Ligands Containing Carboxylate Substituents

Abstract

AbstractIn search of water soluble transition metal complexes with sulfur dominated coordination spheres that model key reactions of nitrogenases, the benzenedithiol derivatives ‘CO2HS2’‐H2 (1) and ‘CO2Me‐S2’‐H2 (2) were synthesized as precursors for multidentate sulfur ligands. The template alkylation of 2 by C2H4Br2 at [Fe(CO)2] fragments yielded a mixture of two diastereomeric C2 symmetrical [Fe(CO)2(‘CO2Me‐S4’)] complexes (4a and 4b), which were separated by crystallization. The hydrolysis of the mixture of the diastereomers 4a and 4b led to the isomerically pure tetradentate thioether thiol ligand ‘CO2Me‐S4’‐H2 (5) proving the regioselectivity of the template alkylation of the asymmetrical dithiol 2. The C1 symmetrical [Fe(‘CO2Me‐S2’)2]2‐ anion is an intermediate of the template alkylation and was isolated as (AsPh4)2 [Fe(‘CO2Me‐S2’2] (11), 4a, 5 and 11 were characterized by X‐ray structural analysis. Saponification of the methyl ester groups of 5 yielded ‘CO2H‐S4’‐H2 (7). Treatment of 7 with FeCl2 · 4 H2O in the presence of CO and LiOMe gave a mixture of two C2 symmetrical and water soluble diastereomers of Li2[Fe(CO)2(‘CO2‐S4’)] (8). Upon treatment with [RuCl2 (PPh3)3] 7 yielded isomerically pure [Ru(PPh3)2‐(‘CO2H‐S4’)] (9). 9 also exhibits C2 symmetry and could be reversibly deprotonated to form the water soluble complex K2[Ru(PPh3)2 (‘CO2‐S4’)] (10). Treatment of (NBu4)2 (‘CO2MeS2’) with “Ru(NO)Cl3” led to isomerically pure (NBu4)[Ru(NO)(‘CO2Me‐S2’)2] (12).