Dynamic Behavior and Isomerization Equilibria of Distannenes Synthesized by Tin Hydride/Olefin Insertions: Characterization of the Elusive Monohydrido Bridged Isomer.

Academic Article


  • The tin(II) hydride [AriPr6Sn(μ-H)]2(AriPr6 = C6H3-2,6(C6H2-2,4,6-iPr3)2) (1a) reacts with 2 equiv of ethylene or t-butylethylene at ca. 25 °C to yield Sn2(AriPr6)2R2(R = ethyl or t-butylethyl), which exist either as a symmetric distannene AriPr6(R)SnSn(R)AriPr6 (2a or 5a) or an unsymmetric stannylstannylene AriPr6SnSnR2AriPr6 (3a). In contrast, the less crowded Sn(II) hydride [AriPr4Sn(μ-H)]2 (AriPr4 = C6H3-2,6(C6H3-2,6-iPr2)2) (1b) reacts with excess ethylene to give AriPr4(CH2CH3)2Sn(CH2CH2)Sn(CH2CH3)(CHCH2)AriPr4 (4) featuring five ethylene equivalents, one of which is dehydrogenated to an vinyl, -CH═CH2, group. The AriPr4 isomers of 2a and 3a, i.e., [AriPr4Sn(C2H5)]2 (2b) and AriPr4SnSn(C2H5)2AriPr4 (3b) are obtained by reaction of [AriPr4Sn(μ-Cl)]2 with EtLi or EtMgBr. The isomeric pairs 2a and 3a are separated by crystallization at different temperatures. Variable-temperature 1H NMR spectroscopy indicates fast ethyl group exchange between Ar(C2H5)SnSn(C2H5)Ar (Ar = AriPr6 (2a) or AriPr4 (2b)) and ArSnSn(C2H5)2Ar (Ar = AriPr6 (3a) or AriPr4 (3b)) with ΔG⧧ = 14.2 ± 0.65 kcal mol-1 for 2a/3a and 14.8 ± 0.36 kcal mol-1 for 2b/3b. The bulkier distannenes [ArSn(CH2CH2tBu)]2 (Ar = AriPr6 (5a) or AriPr4 (5b)), obtained from 1a or 1b and t-butylethylene, dissociate to ArSnCH2CH2tBu monomers in solution. At lower temperature, they interconvert with their stannylstannylene isomers with parameters Keq = 4.09 ± 0.16 for 5a and 6.38 ± 0.41 for 5b and ΔGeq = -1.81 ± 0.19 kcal mol-1 for 5a and -1.0 ± 0.03 kcal mol-1 for 5b at 298 K. The 1:1 reaction of 1a or 1b with 5a or 5b yields the unknown monohydrido species Sn2RHAr2 which has the structure AriPr6Sn-Sn(H)(CH2CH2tBu)AriPr6 (6a) or the monohydrido bridged AriPr4S n(μ-H)S n(CH2CH2tBu)AriPr4 (6b). The latter represents the first structural characterization of a monohydrido bridged isomer of a ditetrelene.
  • Authors

  • Wang, Shuai
  • McCrea-Hendrick, Madison L
  • Weinstein, Cory M
  • Caputo, Christine
  • Hoppe, Elke
  • Fettinger, James C
  • Olmstead, Marilyn M
  • Power, Philip P
  • Status

    Publication Date

  • May 17, 2017
  • Has Subject Area

    Digital Object Identifier (doi)

    Pubmed Id

  • 28398749
  • Start Page

  • 6586
  • End Page

  • 6595
  • Volume

  • 139
  • Issue

  • 19