Reaction of (mu-S)(2)Fe-2(CO)(6) dianion with 1,2-vinyl and aryl diiodides

The inorganic dithiolate, (mu-S)(2)Fe-2(CO)(6)(2-), reductively deiodinates trans-1,2-diiodo-1,2-diphenylethene to afford diphenylacetylene in 79% yield. Reaction of (mu-S)(2)Fe-2(CO)(6)(2-) with 1,2-diiodobenzene and 2,3-diiodotoluene results in the formation of the benzenedithiolate complex (mu-S2C6H4)Fe-2(CO)(6) and toluenedithiolate complex (mu-S2C6H4Me)Fe-2(CO)(6) in 42% and 48% isolated yields, respectively. These reactions appear to involve reductive deiodination of 1,2-diiodobenzene and 2,3-diiodotoluene with (mu-S)(2)Fe-2(CO)(6)(2-) to the corresponding benzynes followed by trapping with the concomitantly formed disulfide (mu-S-2)Fe-2(CO)(6), to give the observed complexes. As such, these reactions involve the first examples of thermal [2+2] cycloaddition of benzyne to the S-S bond of an inorganic disulfide. Although the reaction was not observed on treatment of other substituted 1,2-diiodobenzenes, 1,2,4,5-tetraiodobenzene was monodeiodinated to 1,2,4-triiodobenzene in 62% isolated yield.