Synthesis and Characterization of the Homologous M-M Bonded Series Ar'MMAr' (M = Zn, Cd, or Hg; Ar' = C6H3-2,6-(C6H3-2,6-Pr'2)2) and Related Arylmetal Halides and Hydride Species.

The synthesis and structural characterization of the first homologous, molecular M-M bonded series for the group 12 metals are reported. The compounds Ar′MMAr′ (M = Zn, Cd, or Hg; Ar′ = C6H3-2,6-(C6H3-2,6-Pr′2)2) were synthesized by reduction of the corresponding arylmetal halides by alkali metal! graphite (Zn or Hg) or sodium hydride (Cd). These compounds possess almost linear C-M-M-C core structures with two-coordinate metals. The observed M-M bonds distances were 2.3591(9), 2.6257(5), and 2.5738(3) Å for the zinc, cadmium, and mercury species, respectively. The shorter Hg-Hg bond in comparison to that of Cd-Cd is consistent with DFT calculations which show that the strength of the Hg- Hg bond is greater. The arylmetal halides precursors (Ar′Ml)1 or 2, and the highly reactive hydrides (Ar′MH)1 or 2, were also synthesized and fully characterized by X-ray crystallography (Zn and Cd) and multinuclear NMR spectroscopy. The arylzinc and arylcadmium iodides have iodide-bridged dimeric structures, whereas the arylmercury iodide, Ar′Hgl, is monomeric. The aryizinc and arylcadmium hydrides have symmetric (Zn) or unsymmetric (Cd) p-H-bridged structures. The Ar′HgH species was synthesized and characterized by spectroscopy, but a satisfactory refinement of the structure was precluded by the contamination of monomeric Ar′HgH by Ar′H. It was also shown that the decomposition of Ar′Cd(μ-H)2CdAr′ at room temperature leads to the M-M bonded Ar′CdCdAr′, thereby supporting the view that the reduction of the iodide proceeds via the hydride intermediate. [ABSTRACT FROM AUTHOR]