Journal of the American Chemical Society
Journal of the American Chemical Society
5 years ago

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

Dynamic Behavior and Isomerization Equilibria of Distannenes Synthesized by Tin Hydride/Olefin Insertions: Characterization of the Elusive Monohydrido Bridged Isomer
Madison L. McCrea-Hendrick, Philip P. Power, Cory M. Weinstein, Marilyn M. Olmstead, Shuai Wang, Christine A. Caputo, Elke Hoppe, James C. Fettinger
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 AriPr4Stiebar above startn(μ-H)Stiebar above endn(CH2CH2tBu)AriPr4 (6b). The latter represents the first structural characterization of a monohydrido bridged isomer of a ditetrelene.

Publisher URL: http://dx.doi.org/10.1021/jacs.7b02269

DOI: 10.1021/jacs.7b02269

You might also like
Discover & Discuss Important Research

Keeping up-to-date with research can feel impossible, with papers being published faster than you'll ever be able to read them. That's where Researcher comes in: we're simplifying discovery and making important discussions happen. With over 19,000 sources, including peer-reviewed journals, preprints, blogs, universities, podcasts and Live events across 10 research areas, you'll never miss what's important to you. It's like social media, but better. Oh, and we should mention - it's free.

  • Download from Google Play
  • Download from App Store
  • Download from AppInChina

Researcher displays publicly available abstracts and doesn’t host any full article content. If the content is open access, we will direct clicks from the abstracts to the publisher website and display the PDF copy on our platform. Clicks to view the full text will be directed to the publisher website, where only users with subscriptions or access through their institution are able to view the full article.