Reaction of Hydrogen or Ammonia with Unsaturated Germanium or Tin Molecules under Ambient Conditions: Oxidative Addition versus Arene Elimination
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- 作者：Yang Peng ; Jing-Dong Guo ; Bobby D. Ellis ; Zhongliang Zhu ; James C. Fettinger ; Shigeru Nagase ; Philip P. Power
- 刊名：Journal of the American Chemical Society
- 出版年：2009
- 出版时间：November 11, 2009
- 年：2009
- 卷：131
- 期：44
- 页码：16272-16282
- 全文大小：600K
- 年卷期：v.131,no.44(November 11, 2009)
- ISSN：1520-5126
文摘
The reactions of hydrogen or ammonia with germylenes and stannylenes were investigated experimentally and theoretically. Treatment of the germylene GeAr#2 (Ar# = C6H3-2,6-(C6H2-2,4,6-Me3)2) with H2 or NH3 afforded the tetravalent products Ar#2GeH2 (1) or Ar#2Ge(H)NH2 (2) in high yield. The reaction of the more crowded GeAr′2 (Ar′ = C6H3-2,6-(C6H3-2,6-iPr2)2) with NH3 also afforded a tetravalent amide Ar′2Ge(H)NH2 (3), whereas with H2 the tetravalent hydride Ar′GeH3 (4) was obtained with Ar′H elimination. In contrast, the reactions with the divalent Sn(II) aryls did not lead to Sn(IV) products. Instead, arene eliminated Sn(II) species were obtained. SnAr#2 reacted with NH3 to give the Sn(II) amide {Ar#Sn(μ-NH2)}2 (5) and Ar#H elimination, whereas no reaction with H2 could be observed up to 70 °C. The more crowded SnAr′2 reacted readily with H2, D2, or NH3 to give {Ar′Sn(μ-H)}2 (6), {Ar′Sn(μ-D)}2 (7), or {Ar′Sn(μ-NH2)}2 (8) all with arene elimination. The compounds were characterized by 1H, 13C, and 119Sn NMR spectroscopy and by X-ray crystallography. DFT calculations revealed that the reactions of H2 with EAr2 (E = Ge or Sn; Ar = Ar# or Ar′) initially proceed via interaction of the σ orbital of H2 with the 4p(Ge) or 5p(Sn) orbital, with back-donation from the Ge or Sn lone pair to the H2 σ* orbital. The subsequent reaction proceeds by either an oxidative addition or a concerted pathway. The experimental and computational results showed that bond strength differences between germanium and tin, as well as greater nonbonded electron pair stabilization for tin, are more important than steric factors in determining the product obtained. In the reactions of NH3 with EAr2 (E = Ge or Sn; Ar = Ar# or Ar′), the divalent ArENH2 products were calculated to be the most stable for both Ge and Sn. However the tetravalent amido species Ar2Ge(H)NH2 were obtained for kinetic reasons. The reactions with NH3 proceed by a different pathway from the hydrogenation process and involve two ammonia molecules in which the lone pair of one NH3 becomes associated with the empty 4p(Ge) or 5p(Sn) orbital while a second NH3 solvates the complexed NH3 via intermolecular N−H···N interactions.