Diruthenium Half-Sandwich Complexes Containing One μ-E2 (E = S, Se) Unit and Two Chelating 1,2-Dicarba-closo-dodecaborane-1,2-dithiolate Ligands: Reactivity Studies with Methyl Acetylene Carboxylates

[(p-Cymene)RuCl2]2 reacts with Li2[S2C2(B10H10)] in the presence of excess chalcogen elements to generate dinuclear complexes (p-cymene)Ru(μ-E2)Ru(S2C2B10H10)2, 1S (E = S) and 1Se (E = Se), in which one E−E bridge between the two ruthenium atoms and two chelating 1,2-dicarba-closo-dodecaborane-1,2-dithiolate ligands are present. In 1S and 1Se, one ruthenium atom is surrounded by six chalcogen atoms in a geometry of distorted octahedron and electron-deficient (16e). Treatment of 1S and 1Se with methyl acetylene carboxylates affords addition complexes, (p-cymene)Ru(μ-E2)Ru(S2C2B10H10)2(R1CCR2) (R1 = H (CO2Me), R2 = CO2Me (H), 2S, 2Se (3S, 3Se); R1 = R2 = CO2Me, 4S, 4Se). The terminal alkyne leads to two geometrical isomers that interconvert upon heating. Alkyne addition occurs at sulfur atoms of two different dithiolate ligands that leads to a change of 16e Ru(IV) in 1S and 1Se to 18e Ru(II) in 2S−4S and 2Se−4Se, respectively. The complexes were characterized by IR, MS, NMR spectroscopy, and microanalysis. X-ray structural analyses were performed on 1S−4S and 2Se−4Se.