title: Dynamic Behavior and Isomerization Equilibria of Distannenes Synthesized by Tin Hydride/Olefin Insertions: Characterization of the Elusive Monohydrido Bridged Isomer.
abstract: 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 AriPr4isomers of 2a and 3a, i.e., [AriPr4Sn(C2H5)]2(2b) and AriPr4SnSn(C2H5)2AriPr4(3b) are obtained by reaction of [AriPr4Sn(μ-Cl)]2with EtLi or EtMgBr. The isomeric pairs 2a and 3a are separated by crystallization at different temperatures. Variable-temperature1H 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-1for 2a/3a and 14.8 ± 0.36 kcal mol-1for 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-1for 5a and -1.0 ± 0.03 kcal mol-1for 5b at 298 K. The 1:1 reaction of 1a or 1b with 5a or 5b yields the unknown monohydrido species Sn2RHAr2which 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.affiliation: Department of Chemistry, University of California , 1 Shields Avenue, Davis, California 95616, United States.
authors.forename: Shuai
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Chemistry, University of California , 1 Shields Avenue, Davis, California 95616, United States.
authors.forename: Madison L
authors.initials: ML
authors.lastname: McCrea-Hendrick
authors.affiliation: Department of Chemistry, University of California , 1 Shields Avenue, Davis, California 95616, United States.
authors.forename: Cory M
authors.initials: CM
authors.lastname: Weinstein
authors.affiliation: Department of Chemistry, University of California , 1 Shields Avenue, Davis, California 95616, United States.
authors.forename: Christine A
authors.initials: CA
authors.lastname: Caputo
authors.affiliation: Department of Chemistry, University of California , 1 Shields Avenue, Davis, California 95616, United States.
authors.forename: Elke
authors.initials: E
authors.lastname: Hoppe
authors.affiliation: Department of Chemistry, University of California , 1 Shields Avenue, Davis, California 95616, United States.
authors.forename: James C
authors.initials: JC
authors.lastname: Fettinger
authors.affiliation: Department of Chemistry, University of California , 1 Shields Avenue, Davis, California 95616, United States.
authors.forename: Marilyn M
authors.initials: MM
authors.lastname: Olmstead
authors.affiliation: Department of Chemistry, University of California , 1 Shields Avenue, Davis, California 95616, United States.
authors.forename: Philip P
authors.identifier: 0000-0002-6262-3209
authors.initials: PP
authors.lastname: Power