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

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.

Novel silatranes containing urea functionality have been synthesized from N-[3-(triethoxysilyl)propyl]morpholine-4-carboxylic acid amide, 1-[3-(triethoxysilyl)propyl]-3-phenylurea, 1,2-bis{N′-[3-(triethoxysilyl)propyl]ureido}-ethane and N-[3-(triethoxysilyl)propyl]-N′-[3-(triethoxysilyl)propyl]urea. Single crystal X-ray studies revealed distorted trigonal bipyramidal coordination for Si in N-(3-silatranylpropyl)morpholine-4-carboxylic acid amide and 1-(3-silatranylpropyl)-3-phenylurea with Si–N bond distance of 2.121(1) Å and 2.189(2) Å, respectively.Figure optionsDownload as PowerPoint slideHighlights
► Synthesis of novel silatranes bearing substituted urea functionality.
► Precursors for silatranes are 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]-N0-[3-(triethoxysilyl)propyl]urea (4).
► Transesterification of triethoxysilanes with triethanolamine forms corresponding silatranes.
► Silatranes obtained are 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)-N0-(3-silatranylpropyl)urea (8).
► Silatranes, 5 and 6 show trigonal bipyramidal coordination for Si Si–N bond distance of 2.121(1) Å and 2.189(2) Å, respectively.