title: Aggregation of donor base stabilized 2-thienyllithium in a single crystal and in solution: distances from X-ray diffraction and the nuclear Overhauser effect.
abstract: Various 2-thienyllithium derivatives were investigated in the solid state by X-ray diffraction and in solution by 2D NMR experiments. The determined structures of [(Et(2)O)Li(C(4)H(3)S)](4) (1), [(THF)(2)Li(C(4)H(3)S)](2) (2), [(DME)Li(C(4)H(3)S)](2) (3), [(TMEDA)Li(C(4)H(3)S)](2) (4), and [(PMDETA)Li(C(4)H(3)S)] (5) (DME = 1,2-dimethoxyethane, TMEDA = N,N,N',N'-tetramethylethylene-1,2-diamine, and PMDETA = N,N,N',N",N"-pentamethyldiethylenetriamine) were solved in nondonating toluene and provide firm ground for diffusion-ordered NMR spectroscopy as well as heteronuclear Overhauser enhancement NMR spectroscopy. The distance relation of nuclear Overhauser effects with a factor of r(-6) is employed to gain further insight into the aggregation degree of 1-5 in solution. Comparison of the slope provided by the linear region of the buildup curves and of the ∑r(-6) calculated distances from the crystal structures offers a handle to judge the structure retention versus conversion in solution. The structures of 3-5 are maintained in toluene solution. The data of 2, however, indicate a partial dissociation or a rapid exchange between the vertices of a tetrameric core and free THF molecules. Auxiliary exchange spectroscopy investigations showed that the signals of the nitrogen donor base containing compounds 4 and 5 exchange with the signals of nonlithiated thiophene. This is explained by exchange of the deuterium by a hydrogen atom via lithiation of toluene molecules.
authors.affiliation: Institut für Anorganische Chemie der Universität Göttingen, Tammannstrasse 4, 37077 Göttingen, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Granitzka
authors.forename: Ann-Christin
authors.initials: AC
authors.lastname: Pöppler
authors.forename: Eike K
authors.initials: EK
authors.lastname: Schwarze
authors.forename: Daniel
authors.initials: D
authors.lastname: Stern
authors.forename: Thomas
authors.initials: T
authors.lastname: Schulz
authors.forename: Michael
authors.initials: M
authors.lastname: John
authors.forename: Regine
authors.initials: R
authors.lastname: Herbst-Irmer
authors.forename: Sushil K
authors.initials: SK
authors.lastname: Pandey
authors.forename: Dietmar
authors.initials: D
authors.lastname: Stalke