Bis(2,3-naphthalindiolato)[2-(pyrrolidinio)ethyl]silicat: Synthese und strukturelle charakterisierung eines zwitterionischen λ 5-spirosilicates

Abstract

The zwitterionic spirocyclic bis(2,3-naphthalenediolato)[2-(pyrrolidinio)ethyl]silicate [(C 10H 6O 2) 2-SiCH 2CH 2(H)NC 4H 8, 3] was synthesized and its structure characterized (single crystal X-ray structural analysis; 1H, 13C and 29Si NMR studies of solutions in DMSO). 3 was obtained by reaction of cyclohexylmethoxyphenyl(2-pyrrolidinoethyl)silane [C 6H 11(CH 3O)Si(C 6H 5)CH 2CH 2NC 4H 8, 4] with 2,3-dihydroxynaphthalene [C 10H 6(OH) 2] in acetonitrile at room temperature (isolated as 3·CH 3CN, yield 81%). The formation of 3 involves two unusual SiC cleavage reactions (cleavage of SiC 6H 5 and SiC 6H 11 under mild reaction conditions). In addition, 3 was prepared by reaction of 2,3-dihydroxynaphthalene with dimethoxyphenyl(2-pyrrolidinoethyl)silane [C 6H 5(CH 3O) 2SiCH 2CH 2NC 4H 8, 5] and trimethoxy(2-pyrrolidinoethyl)silane [(CH 3O) 3SiCH 2CH 2NC 4H 8, 6], respectively (isolated as 3·CH 3CN; yields 83 and 86%, respectively). 3·CH 3CN crystallizes in the space group Pbca with a = 8.877(2) Å, b = 22.823(4) Å, c = 24.597(4) Å, and Z = 8 ( R = 0.0592, R w = 0.0529). The pentacoordinated Si atom of 3·CH 3CN is surrounded by its ligands in a nearly ideal square-pyramidal fashion (four basal O atoms and one apical C atom). The CH 3CN molecule does not coordinate to the Si atom.