title: NMR studies of dilithiostyrenes: aggregation, NMR parameters, and DFT calculations for (E)-1-Lithio-2-(o-lithiophenyl)-1-trimethylsilylethene.
abstract: The dilithio compound (E)-1-lithio-2-(o-lithiophenyl)-1-trimethylsilylethene (5) was synthesized from 2-trimethylsilylbenzo-[b]tellurophene (6) with lithium-6 and a detailed analysis of its1H,6Li,13C, and29Si NMR spectra showed 5 to form a dimer 52in tetrahydrofuran and diethylether, while addition of tetramethylethylenediamine stabilizes a monomer 51. A monomer-dimer equilibrium exists with K at 230 K = 1.25 and ΔG230o = -0.43 kJ mol-1. Homonuclear6Li,6Li coupling of 0.25 ± 0.07 Hz in the dimer was detected by a 1D-6Li,6Li INADEQUATE experiment, and scalar6Li,13C coupling constants were obtained from13C satellites in the6Li spectrum, from13C multiplet simulation and6Li,13C-HMQC spectra. In addition, structures and coupling constants of 51and 52were calculated by density functional theory (DFT) methods. It was found that the magnitude of the6Li,13C spin-spin interactions shows an inverse correlation with the C-Li bond lengths. The intra-aggregate exchange in the dimer, caused by 180° rotation of one monomer unit within the solvent cage, was studied by6Li DNMR and line shape analysis and yielded ΔG298≠ = 60 ± 3 kJ mol-1; ΔH≠= 84 ± 3 kJ mol-1; ΔS≠= 80 ± 3 J mol-1K-1for this process. Copyright © 2015 John Wiley & Sons, Ltd.
authors.affiliation: Faculty IV, OCII, University of Siegen, D-57068, Siegen, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Böhler
authors.affiliation: Faculty IV, OCII, University of Siegen, D-57068, Siegen, Germany.
authors.forename: Harald
authors.initials: H
authors.lastname: Günther
authors.affiliation: Faculty IV, OCII, University of Siegen, D-57068, Siegen, Germany.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Reider
authors.affiliation: Faculty IV, OCII, University of Siegen, D-57068, Siegen, Germany.
authors.forename: Adalbert
authors.initials: A
authors.lastname: Maercker
authors.affiliation: Institute of Organic Chemistry, University of Giessen, Heinrich-Buff-Ring 58, D-35392, Giessen, Germany.
authors.forename: Dennis
authors.initials: D
authors.lastname: Gerbig
authors.affiliation: Institute of Organic Chemistry, University of Giessen, Heinrich-Buff-Ring 58, D-35392, Giessen, Germany.
authors.forename: Heike
authors.initials: H
authors.lastname: Hausmann
keywords: 13C-NMR; 1H-NMR; 29Si-NMR; 6Li-NMR; DNMR; NMR; aggregation; exchange; organolithium compounds