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.
Two isomers of the [Co(tren)(D-Glc1A1,2H −2 -κ 2 O 1,2 )] + (1) chelate are formed in equal parts in the reaction of [Co(tren)Cl 2 ]Cl and sodium gluconate. In contrast, the gluconate's 2-amino-2-deoxy derivative glucosaminate formed a single isomer of [Co(tren)(2). Crystals of the OC-6-34 isomer of 1, [1a]PF 6 ·H 2 O, showed the support of the metal-binding site by intramolecular hydrogen bonds. Due to the inertness of the cobalt(III) chelates, spectroscopy on redissolved crystals of [1a]PF 6 ·H 2 O allowed the separation of the two 13 C NMR signal sets of the isomeric mixture. In a DFT approach, a small energy difference explained the formation of two isomers in the case of the gluconate. A larger difference was obtained for the glucosaminate, in line with the known rules for the stereospecific amino acid-Co(tren) chelation.
Sialic acid represents a group of thirty derivates of neuraminic acid with various substituents at the amino residue and the alcoholic hydroxy groups. We analysed the behaviour of the tetracoordinated metal ions palladium(II) and silicon(IV) against the most important derivative N-acetylneuraminic acid (NANA). The molecular 77 structures were assigned by a combined 1 H, 13 C and 29 Si NMR-spectroscopic approach. Despite the presence of many different functional groups, the coordination chemistry of NANA with Pd II follows established rules. Coordination via the N-acetyl-group -sterically impossible with Pd II -was realised with Si IV .
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