Synthesis and characterization of the monomeric diaryls M{C6H3-2,6-Mes(2)}(2) (M=Ge, Sn, or Pb; Mes=2,4,6-Me3C6H2-) and dimeric aryl-metal chlorides [M(Cl){C6H3-2,6-Mes(2)}](2) (M=Ge or Sn)

The reaction of 2 equiv of LiC6H3-2,6-Mes(2) (Mes = 2,4,6-Me3C6H2-) with GeCl2 . dioxane, SnCl2, or PbCl2 in ether solution has resulted in the isolation of rare examples of monomeric, sigma-bonded, diaryl derivatives M{C6H3-2,6-Mes(2)}(2) (M = Ge (1), Sn (2), or Pb (3)). The compounds 1-3 are thermally stable, purple, crystalline solids with V-shaped geometries and remarkably wide (ca. 114.5 degrees) interligand bond angles. The monoaryl metal chloride derivatives [M(Cl){C6H3-2,6-Mes(2)}](2) (M = Ge (4) or Sn (5)) were isolated by treatment of the appropriate dichlorides with either 1 equiv of LiC6H3-2,6-Mes(2) or 1 equiv of the diaryls 1 or 2. The orange germanium compound 4 has a dimeric structure in which the monomers are linked by a relatively weak, 2.443(2) Angstrom, Ge-Ge interaction. In sharp contrast, its yellow tin analogue 5 has a dimeric structure in which three-coordinate tin centers are associated by asymmetrically bridging chlorides. The compounds 1-3 constitute a unique, structurally characterized diaryl series for Ge, Sn, and Pb and display evidence of steric crowding that is significantly greater than that observed in previously known sigma-bonded diorgano group 14 derivatives. The compounds 4 and 5 are the first fully structurally characterized organometal halide derivatives of Ge or Sn in which the organic ligand is monodentate, purely sigma-bonded, and nonchelating.