New silatranes possessing urea functionality: Synthesis, characterization and their structural aspects

Abstract

The present work aims at the synthesis of various novel silatranes bearing substituted urea functionality. Nucleophilic addition of various amines (morpholine, aniline, ethylenediamine and 3-aminopropyltriethoxysilane) to 3-isocyanatopropyltriethoxysilane resulted in the four triethoxysilanes; N-[3-(triethoxysilyl)propyl]morpholine-4-carboxylic acid amide ( 1), 1-[3-(triethoxysilyl)propyl]-3-phenylurea ( 2), 1,2-bis{ N′-[3-(triethoxysilyl)propyl]ureido}-ethane ( 3) and N-[3-(triethoxysilyl)propyl]-N′-[3-(triethoxysilyl)propyl]urea ( 4), respectively. In the presence of a base the resulting silanes undergo transesterification reaction with triethanolamine, thus forming the corresponding silatranes, N-(3-silatranylpropyl)morpholine-4-carboxylic acid amide ( 5), 1-(3-silatranylpropyl)-3-phenylurea ( 6), 1,2-Bis[ N′-(3-silatranylpropyl)ureido]-ethane ( 7) and N-(3-silatranylpropyl)-N′-(3-silatranylpropyl)urea ( 8), respectively. Among these are four novel compounds ( 5– 8), which were characterized by elemental analysis, IR, multinuclear ( 1H, 13C and 29Si) NMR and mass spectroscopy. Structures of compounds 5 and 6 were deduced by X-ray crystallography. Single crystal X-ray studies revealed distorted trigonal bipyramidal coordination about Si in 5 and 6 with Si–N bond distance of 2.121(1) Å and 2.189(2) Å, respectively.