Synthesis and reactivity investigations of group 14 unsaturated molecules

This thesis explores the effects of modified terphenyl ligands on the chemistry of heavier group 14 alkyne analogues. The synthesis and characterization of a series of digermynes and distannynes (germanium and tin substituted analogues of alkynes) stabilized by terphenyl ligands were described. The terphenyl ligands employed are based on the Ar' (Ar' = C6H3-2,6(C 6H3-2,6-iPr2)2) or Ar* (Ar* = C6H3-2,6(C6H2-2,4,6- iPr3)2) modified by different substituents at the meta or para position of their central aryl rings to yield 4-X-Ar' (4-X-Ar' = 4-X-C6H2-2,6(C6H3-2,6- iPr2)2, X = H, F, Cl, OMe, tBu, SiMe3, GeMe3) and 3,5-iPr2-Ar' or Ar* and 3,5-iPr2-Ar*. The terphenyl germanium (II) or tin (II) halides precursors were obtained by the reaction of one equivalent of the lithium terphenyl salt with GeCl2.dioxane or SnCl2 . For germanium, their X-ray crystal structures showed them to be either Ge-Ge bonded dimers with trans-pyramidal geometries or V-shaped monomers in the case of the bulkiest terphenyls. In contrast, the corresponding tin derivatives displayed no tin-tin bonding but existed either as halide bridged dimers or monomers. Reduction of the Ge and Sn precursors with a variety of reducing agents afforded the digermynes ArGeGeAr (Ar = 4-Cl-Ar', 4-Me3Si-Ar' or 3,5-iPr2-Ar*) or the distannynes ArSnSnAr (Ar = 4-F-Ar', 4-Cl-Ar', 4-MeO-Ar', 4-tBu-Ar', 4-Me3Si-Ar', 4-Me3Ge-Ar', 3,5-iPr2-Ar', 3,5- iPr2-Ar*). These compounds were characterized structurally and spectroscopically. The data showed that digermynes display planar trans-bent core geometries consistent with Ge-Ge multiple bonding with Ge-Ge distances near 2.26 A and bending angles near 128°.;Small molecule activation by unsaturated main group compounds is also described in this dissertation. Dihydrogen reacts directly with a range of distannynes at ca. 25° under one atmosphere pressure to afford symmetric hydrogen bridged or unsymmetric stannylstannane products in high yield. The reactions of hydrogen or ammonia with germylenes and stannylenes were investigated experimentally and theoretically. Treatment of the germylene GeAr...