Abstract
In the search for complexes, having sulfur‐dominated coordination spheres, that potentially bind, activate, or stabilize nitrogenase‐relevant small molecules, we have synthesized several ruthenium−sulfur complexes of the type [Ru(L)(pyS~4~)] starting from the labile acetonitrile complex [Ru(NCMe)(pyS~4~)] (2). Complex 2 was obtained from the reduction of [Ru(NO)(pyS~4~)]Br (1) by N~2~H~4~·H~2~O in the presence of MeCN. The acetonitrile ligand in 2 could be exchanged for the soft σ−π ligand CO to give [Ru(CO)(pyS~4~)] (3). Attempts to coordinate N~2~ to the pyS~4~^2−^ fragment of 2 gave [{Ru(pyS~4~)}~2~] (4). Complex 2 reacts also with hard σ‐ligands, such as N~2~H~4~, NH~3~, pyridine, and pyrazine, to afford mononuclear [Ru(N~2~H~4~)(pyS~4~)] (5), [Ru(NH~3~)(pyS~4~)] (6), [Ru(py)(pyS~4~)] (7), and [Ru(pyr)(pyS~4~)] (8), respectively. Reaction of 2 with NEt~4~N~3~ resulted in the formation of NEt~4~[Ru(N~3~)(pyS~4~)] (9). The oxidation of 2 with I~2~ afforded [Ru(I)(pyS~4~)] (10). The protonated and alkylated species [Ru(NCMe)(pyS~4~‐H)]BF~4~ (11), [Ru(NCMe)(pyS~4~‐Et)]BF~4~ (12), and [{Ru(pyS~4~‐Et)}~2~] (BF~4~)~2~ (13) were obtained from 2 by its treatment with HBF~4~ or Et~3~OBF~4~. The N~2~H~4~ ligand in 5 could not be oxidized to N~2~H~2~: the oxidation of the Ru^II^ center to Ru^III^ takes place instead. Attempts to oxidize 5 using either [FeCp~2~]PF~6~ or I~2~ gave {Ru^II/III^(pyS~4~)}~2~ (14) and [Ru^III^(NH~3~)(pyS~4~)]X (X = PF~6~, I) (15, 16). The oxidation of 3 and 6 by NOBF~4~ gave Ru^III^ species of [Ru^III^(CO)(pyS~4~)]BF~4~ (17) and [Ru^III^(NH~3~)(pyS~4~)]BF~4~ (18). The oxidation of 5 and 6 with H~2~O~2~ afforded [{Ru^II^(pyS~4~−O~3~)}~2~] (19), [{Ru^II^(pyS~4~−O~4~)}~2~] (20) and [Ru^II^(NH~3~)(pyS~4~−O~4~)] (21). All complexes were characterized by spectroscopic methods and by elemental analysis. The molecular structures of 4, 6, 10, 14, 15, 19, and 20 were determined by X‐ray crystallographic analyses. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)