Synthesis, structures and stereodynamic behavior of novel pentacoordinate (O→Si)-Chelate Difluoro(methyl)silylmethyl derivatives of amides and imides

Publication date: Available online 24 July 2018Source: Journal of Organometallic ChemistryAuthor(s): Vadim V. Negrebetsky, Eugeniya P. Kramarova, Aleksander G. Shipov, Yuri I. Baukov, Alexander A. Korlyukov, Dmitry E. Arkhipov, Alan R. Bassindale, Peter G. Taylor, Sergey Yu BylikinAbstractThe structures and stereodynamic behavior of (O→Si)-chelate methyldifluorosilanes in solutions were studied by multinuclear (1H, 13C, 19F, 29Si) and 2D (COSY, HETCOR 1H, 13C) NMR spectroscopy. The range of studied complexes included amides RC(O)N(R')CH2SiMeF2 [R = Ph, R' = H (1a); R = R' = Me (1b); R = Me, R' = CHMePh (1c)], lactams LCH2SiMeF2 (L = 2-oxoazepan-1-yl (2a), 2,2-dimethyl-4-oxo-2H-benzo[1,3]oxazin-3-yl (2b) or 4-methyl-2-oxoquinolin-1-yl (2c)] and the six-membered imide Im6CH2 [2,6-dioxopiperidin-1-yl (3)]. The pentacoordination of silicon atoms in all studied compounds was confirmed by NMR study in solutions and single-crystal X-ray studies of complexes 1c, 2a, 2c and 3. The temperature dependency observed for 19F NMR signals in solution was explained by the ligand exchange in the coordination environment of silicon atoms (permutational isomerization) and used for determining the activation parameters of this process by 19F DNMR. Quantum-chemical calculations for various isomers of complexes 1c, 2a, 2c and 3 suggested the “turnstile rotation” as the most likely mechanism for the observed stereodynamic processes.Graphical abstract
Source: Journal of Organometallic Chemistry - Category: Chemistry Source Type: research