ISSN:
0009-2940
Keywords:
Silicon
;
Configuration determination
;
Aminosilanes
;
Tetra(amino)silanes
;
Molecular conformation
;
Conformation analysis
;
Nitrogen
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
In a search for crystalline homoleptic tetra(amin)silanes with (mirror)-symmetrical NR2 substituents, tetrakis( 1-pyrrolidinyl)silane (1) was prepared by an improved synthetic route, and tetrakis(morpholino)silane (2) was synthesized from SiBr4 and morpholine/Li-morpholide via the intermediate BrSi[N(CH2CH2)2O]3 (4). With SiCl4 only the monochloro stage, 3, is reached. Tetrakis(4-methyl-1-piperazinyl)silane (5) was prepared similarly, using 4-methylpiperazine. With (CH2)6NH or (CH2)6NLi and SiBr4 only [(CH2)6N]3SiBr (6) was obtained. The structures of 1, 2 and 5 were determined by single-crystal X-ray diffraction. While compound 1 has an irregular molecular geometry following no symmetrical pattern, molecules of 2 and 5 have similar structures with almost superimposable Si(NC2)4 cores of approximate D2d symmetry. The overall molecular symmetry of 2 is reduced only by incongruous folding of the heterocycles, which are all in a chair conformation. The core structures of 2 and 5 are in excellent agreement with the results of density function calculations for Si(NH2)4. Si(NMe2)4 (the crystal structure of which could not be determined) was converted into (Me2N)3SiO-SO2CF3 (7) by treatment with two equivalents of triflic acid. Reaction of 7 with 1-naphthylamine/triethylamine affords (Me2N)3SiNHC9H7 (8). With 2,4-difluoroaniline/NEt3 the analogous derivative (Me2N)3SiNHC6H3F2 (9) is obtained, but with 4-bromoaniline the product is a silane with the ligands redistributed to give (Me2N2),Si(NHC6H4Br), (10), the structure of which was also determined. It has a non-standard geometry with very flat nitrogen pyramids at all four substituents.
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19971300821
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