Synthesis and reaction chemistry of homonuclear metal-metal bonded group 12 (zinc, cadmium and mercury) and group 13 (gallium and indium) organometallic compounds ArMMAr (Ar = terphenyl ligands) and related 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-(C6 H3-2,6-Pri2) 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) A for the zinc, cadmium and mercury species, respectively. DFT calculations show that the M-M bonds have significant p-character. The related arylmetal hydrides (Ar'MH)1 or 2 were also synthesized and fully characterized by X-ray crystallography (Zn and Cd) and multinuclear NMR spectroscopy, which provide unambiguous supporting evidence for M-M bonds in Ar'MMAr'. Study on metal hydride Ar* derivatives (Ar* = C6H3-2,6-(C6H 2-2,4,6-Pri3)2) sheds light on the associative M-H cleavage pathway of group 12 metal hydrides to afford the M-M bonded species.;A series of stable aryl gallium(I) terphenyl derivatives was synthesized and characterized. Dimeric structures with trans-bent planar CGaGaC core arrangements were observed for (GaAr*-4-But)2 and (GaAr*-4-CF 3)2, whereas monomeric structures featuring one coordinate gallium were observed for the more crowded complexes GaAr*-3,5-Pri 2 and GaAr'-3,5-Pri2. These structural observation as well as spectroscopic and computational data suggested that the Ga-Ga bond in the neutral ArGaGaAr dimers is very weak, and an angular closure and the resulting increased steric effect in 3,5-Pri 2-Ar* and 3,5-Pri2-Ar' is sufficient to prevent Ga-Ga bond formation. The reaction chemistry of low valent ArGaGaAr (Ar = Ar' or 4-SiMe3-Ar') towards H2, NH3, phenylacetylene and alkenes (ethylene, propene and styrene) have also been performed at room temperature and 1 atmosphere pressure. The oxidative insertion products were afforded. The dimeric arylgallium/indium chalcogenides of formula [Ar'ME] 2 (M = Ga or In, E = O or S) were synthesized by the treatment of Ar'MMAr' with N2O or elemental sulfur. Their low oxidation heavier group 13/group 16 chalcogenolate isomers of formula [Ar'EM]2 (M = In or Tl, E = O or S) were also synthesized and fully characterized.