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Dibutylsilylene Derivatives of Tartaric Acid



Crystals of the bis(tert-butyl)silylene (DTBS) derivatives of the tartaric acids were synthesized from D-, L-, rac-, and meso-tartaric acid and DTBS bis(trifluoromethanesulfonate): two polymorphs of Si2tBu4(L-Tart1,2;3,4H–4) (L-1a and L-1b), the mirror image of the denser modification (D-1b) as well as the racemate (2), and the meso analogue Si2tBu4(meso-Tart1,3;2,4H–4) (3). The structures were determined by single-crystal X-ray diffraction. The threo-configured D- and L- (and rac-) tartrates were coordinated by two tBu2Si units forming five-membered chelate rings, whereas the erythro-configured meso-tartrate formed six-membered chelate rings. The new compounds were analyzed by NMR techniques, including 29Si NMR spectroscopy, and single-crystal X-ray crystallography.