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

series of anionic phenylsilicon(IV) bis-catecholate complexes, where (Cat 1 ) – = catecholate, (Cat 2 ) – = 3,4,5,6-tetrabromocatecholate, (Cat 3 ) – = 4-cyanocatecholate, (Cat 4 ) – = 4-nitrocatecholate, (Cat 5 ) – = 3-fluorocatecholate, and (Cat 6 ) – = 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 1 H, 13 C, and 29 Si NMR spectra, voltammetry, and ESR. The heteroligand anionic phenylsilicon(IV) complexes crystallized from solutions as salts (Chex 2 NH 2 )[PhSi(Cat 1 ) 2 ] ( I ), (Chex 2 NH 2 )-[PhSi(Cat 2 ) 2 ]·0.5C 6 H 14 ( II ), (Chex 2 NH 2 )[PhSi(Cat 3 ) 2 ]·2C 6 H 6 ( III ), (Chex 2 NH 2 )[PhSi(Cat 4 ) 2 ]· H 2 O ( IV ), (Chex 2 NH 2 )[PhSi(Cat 5 ) 2 ] ( V ), and (Chex 2 NH 2 )[PhSi(Cat 6 ) 2 ] ( VI ) (Chex 2 NH_2^ + = 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 .