Insertion of phenyl isocyanate into the Si-N bond of N-(tri methylsilyl)diethylamine yields the N'-silylated N,N-diethylN'-phenylurea 1, which undergoes transsilylation with SiCl4 to yield the C 3-symmetric cationic hexacoordinate silicon complex 3s+ [tris-Κ-O,N'-(N,N-diethyl-N'-phenylureato)siliconium] as chloride salt, which was characterized crystallographically. The cationic complex. 3s + exhibits a distorted trigonal antiprismatic coordination sphere about the silicon atom with fac arrangement of the three N-atoms (and the three O-atoms) relative to one another. This C3-symmetric complex undergoes isomerization into its asymmetric isomer 3a+ (mer arrangement of NNN or OOO relative to one another) in. CDCl3 solution. Hence, two 29Si NMR signals appear and four sets of signals emerge in the 1H and 13C NMR spectra. Despite its pronounced axial symmetry, the 29Si NMR shielding tensor of the cation 3s+ in its chloride salt exhibits an unusually small span (less than 20 ppm), which was analyzed CP/MAS NMR spectroscopically and by computational methods.
All Science Journal Classification (ASJC) codes
- Inorganic Chemistry