Synthesis, Crystal Structure, and Properties of Phenylsilicon(IV) Bis-catecholate Complexes

Russian Journal of Coordination Chemistry/Koordinatsionnaya Khimiya. 2022. Vol. 48. No. 10. P. 647–658.

Kramarova E. P., Negrebetskii V. V., Volodin A. D., Buikin P., Lalov A. V., Novikov R. A., Aliev T. M., Korlyukov A., Vologzhanina A. V.

Abstract: A series of anionic phenylsilicon(IV) bis-catecholate complexes, where (Cat1)– = catecholate, (Cat2)– = 3,4,5,6-tetrabromocatecholate, (Cat3)– = 4-cyanocatecholate, (Cat4)– = 4-nitrocatecholate, (Cat5)– = 3-fluorocatecholate, and (Cat6)– = 4,5-dibromocatecholate, were prepared by the reaction of trimethoxyphenylsilane with two equivalents of catechol or its derivatives containing electron-withdrawing substituents in the benzene ring in the presence of dicyclohexylamine. The complexes were characterized by IR spectra and 1H, 13C, and 29Si NMR spectra, voltammetry, and ESR. The heteroligand anionic phenylsilicon(IV) complexes crystallized from solutions as salts (Chex2NH2)[PhSi(Cat1)2] (I), (Chex2NH2)-[PhSi(Cat2)2]·0.5C6H14 (II), (Chex2NH2)[PhSi(Cat3)2]·2C6H6 (III), (Chex2NH2)[PhSi(Cat4)2]· H2O (IV), (Chex2NH2)[PhSi(Cat5)2] (V), and (Chex2NH2)[PhSi(Cat6)2] (VI) (Chex2NH2+ = dicyclohexylammonium). The composition and structure of the products were confirmed by X-ray diffraction data (CCDC nos. 2150293–2150297 for I–V, respectively). The effect of substituent in the benzene ring on the electronic structure of the anion was studied by PBE0/6-311G(d,p) quantum chemical calculations with allowance for non-specific solvation (PCM model). The oxidation potentials of II–VI were measured; radical formation upon electrochemical oxidation and reduction was observed for II.

Keywords: crystal structure, quantum chemical calculations, catecholate anion, hypercoordinate silicon