| Title | Dynamic Behavior and Isomerization Equilibria of Distannenes Synthesized by Tin Hydride/Olefin Insertions: Characterization of the Elusive Monohydrido Bridged Isomer. |
|---|---|
| Authors | Wang, S.; McCrea-Hendrick, M.L.; Weinstein, C.M.; Caputo, C.A.; Hoppe, E.; Fettinger, J.C.; Olmstead, M.M.; Power, P.P. |
| Journal | J Am Chem Soc |
| DOI | 10.1021/jacs.7b02269 |
| Abstract |
The tin(II) hydride [Ar((i)Pr6)Sn(μ-H)]2(Ar((i)Pr6) = C6H3-2,6(C6H2-2,4,6-(i)Pr3)2) (1a) reacts with 2 equiv of ethylene or t-butylethylene at ca. 25 °C to yield Sn2(Ar((i)Pr6))2R2(R = ethyl or t-butylethyl), which exist either as a symmetric distannene Ar((i)Pr6)(R)SnSn(R)Ar((i)Pr6) (2a or 5a) or an unsymmetric stannylstannylene Ar((i)Pr6)SnSnR2Ar((i)Pr6) (3a). In contrast, the less crowded Sn(II) hydride [Ar((i)Pr4)Sn(μ-H)]2 (Ar((i)Pr4) = C6H3-2,6(C6H3-2,6-(i)Pr2)2) (1b) reacts with excess ethylene to give Ar((i)Pr4)(CH2CH3)2Sn(CH2CH2)Sn(CH2CH3)(CHCH2)Ar((i)Pr4) (4) featuring five ethylene equivalents, one of which is dehydrogenated to an vinyl, -CH═CH2, group. The Ar((i)Pr4) isomers of 2a and 3a, i.e., [Ar((i)Pr4)Sn(C2H5)]2 (2b) and Ar((i)Pr4)SnSn(C2H5)2Ar((i)Pr4) (3b) are obtained by reaction of [Ar((i)Pr4)Sn(μ-Cl)]2 with EtLi or EtMgBr. The isomeric pairs 2a and 3a are separated by crystallization at different temperatures. Variable-temperature (1)H NMR spectroscopy indicates fast ethyl group exchange between Ar(C2H5)SnSn(C2H5)Ar (Ar = Ar((i)Pr6) (2a) or Ar((i)Pr4) (2b)) and ArSnSn(C2H5)2Ar (Ar = Ar((i)Pr6) (3a) or Ar((i)Pr4) (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(CH2CH2(t)Bu)]2 (Ar = Ar((i)Pr6) (5a) or Ar((i)Pr4) (5b)), obtained from 1a or 1b and t-butylethylene, dissociate to ArSnCH2CH2(t)Bu 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 Ar((i)Pr6)Sn-Sn(H)(CH2CH2(t)Bu)Ar((i)Pr6) (6a) or the monohydrido bridged Ar((i)Pr4)S n(μ-H)S n(CH2CH2(t)Bu)Ar((i)Pr4) (6b). The latter represents the first structural characterization of a monohydrido bridged isomer of a ditetrelene. |
See more Tin products. Tin (atomic symbol: Sn, atomic number: 50) is a Block P, Group 14, Period 5 element with an atomic weight of 118.710. The number of electrons in each of tin's shells is 2, 8, 18, 18, 4 and its electron configuration is [Kr] 4d10 5s2 5p2. The tin atom has a radius of 140.5 pm and a Van der Waals radius of 217 pm.In its elemental form, tin has a silvery-gray metallic appearance. It is malleable, ductile and highly crystalline. 
Tin has nine stable isotopes and 18 unstable isotopes. Under 3.72 degrees Kelvin, Tin becomes a superconductor. Applications for tin include soldering, plating, and such alloys as pewter. The first uses of tin can be dated to the Bronze Age around 3000 BC in which tin and copper were combined to make the alloy bronze. The origin of the word tin comes from the Latin word Stannum which translates to the Anglo-Saxon word tin. For more information on tin, including properties, safety data, research, and American Elements' catalog of tin products, visit the Tin element page.