Aggregation of Donor Base Stabilized 2-Thienyllithium in a Single Crystal and in Solution: Distances from X-ray Diffraction and the Nuclear Overhauser Effect

作者：Granitzka Markus; Poeppler Ann Christin; Schwarze Eike K; Stern Daniel; Schulz Thomas; John Michael; Herbst Irmer Regine; Pandey Sushil K; Stalke Dietmar^*

来源：Journal of the American Chemical Society, 2012, 134(2): 1344-1351.

DOI：10.1021/ja210382c

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 [(Et2O)Li(C4H3S)](4) (1), [(THF)(2),Li(C4H3S)](2) (2), [(DME)Li(C4H3S)](2), (3), [(TMEDA)Li(C4H3S)](2) (4), and [(PMDETA)Li(C4H3S)] (5) (DME = 1,2-dimethoxyethane, TMEDA = N,N,N%26apos;,N%26apos;-tetramethylethylene-1,2-diamine, and PMDETA = N,N,N%26apos;,N%26quot;,N%26quot;-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 Sigma 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.

• 出版日期2012-1-18