Synthesis and electrochemistry of adducts of acetylene and acetylenedicarboxylic acid at sulfurs in sulfur-bridged nitrilotriacetato molybdenum clusters

Acetylene- and acetylenedicarboxylic acid (ADA) adducts were synthesized and characterized of sulfur-bridged trinuclear molybdenum clusters, [Mo3(μ3-S)(μ-S)(μ3-SCH=CHS)(Hnta)3]2- (2) and [Mo3(μ3-S)(μ-SC(COOH)=CH(COOH))(μ3-SC(COOH)=C(COOH)S)(Hnta)3]- (3) obtained through the reaction of [Mo3(μ3-S)(μ-S)3(Hnta)3]2- (1) with the above reagents, respectively. X-ray crystallography of K2[2]·KCl·8 H2O (2′) revealed the existence of two C-S bonds and indicated that the distance of the C-C moiety derived from acetylene is close to that of ethylene (1.33(2) Å). A cyclic voltammogram of 2 showed a one-electron oxidation process, which was not observed in 1. In the reduction side, no appreciable change of the reduction potential was observed in the adduct formation. The clusters 2 and 3 were characterized by 1H NMR and electronic spectroscopy, and the formation mechanism of 3 is discussed, where two kinds of intermediates are proposed: one has two C-S bonds, and the other, one C-S bond, which is caused by the scission with H+. To cite this article: H. Takagi et al., C. R. Chimie 8 (2005).