Reactions of Sulfido-Bridged Molybdenum Dimers with Diynes as a Route to Multinuclear Dithiolene Complexes

The bridging sulfido ligands in dunuclear molybdenum complexes of the formula
(MenCpMoμ-S)2S2CH2, where n = 0 or 1, react with alkynes to form alkenedithiolate complexes. These reactions have been extended to a series of diynes, including 2,4-hexadiyne,
1,4-diphenyl-1,3-butadiyne, 1,3-diethynylbenzene, and 1,4-bis(trimethylsilylethynyl)benzene,
to form bis(alkenedithiolate) complexes. The corresponding mono-adducts have also been
synthesized by the reaction of the molybdenum dimer with the diyne in a 1:1 molar ratio.
The new alkyne adducts have been characterized by spectroscopic techniques and cyclic
voltammetry, and both the 1:1 and 2:1 adducts of 1,4-diphenyl-1,3-butadiyne have been
identified by X-ray structural determinations. Synthetic routes to a hexanuclear complex
and higher molecular weight oligomers linked by alkenedithiolate ligands are also described.
Tetranuclear complexes linked by the 1,3-dialkynes show two closely spaced oxidation waves
in the cyclic voltammogram, suggesting a small degree of electronic communication between
the dimers.