As-As Bond Formation via Reductive Elimination from a Zirconocene Bis(dimesitylarsenide) Compound

A new zirconocene bis(arsenide) derivative, Cp2Zr(AsMes(2))(2) (1; Cp = cyclopentadienyl, Mes = 2,4,6-trimethylphenyl), has been prepared by the metathetical reaction of 2 equiv of LiAsMes(2) with Cp2ZrCl2 and structurally characterized. Efforts to prepare Cp2ZrCl(AsMes(2)) (2) by reaction of 1 equiv of LiAsMes(2) with Cp2ZrCl2 yielded a mixture of products that could not be separated, including 1 and 2, as identified by H-1 NMR spectroscopy. Compound 1 thermally decomposes with formation of As(2)Mes(4), suggestive of reductive elimination to form an As-As bond. Further evidence for reductive elimination comes from effective interception of a putative zirconium(II) intermediate with diphenylacetylene to give Cp2Zr(C4Ph4).