In:
Zeitschrift für Naturforschung B, Walter de Gruyter GmbH, Vol. 48, No. 12 ( 1993-12-1), p. 1693-1706
Abstract:
The zwitterionic A 5 -spirosilicates bis[1,2-benzenediolato(2–)][(morpholinio)methyl] silicate (1), bis[2,3-naphthalenediolato(2–)][(morpholinio)methyl] silicate (2; isolated as 2 • CH 3 CN), bis[1,2-benzenediolato(2–)][3-(morpholinio)propyl] silicate (3) and bis[2,3-naphthalenediolato(2 –)][3-(morpholinio)propyl] silicate (4; isolated as 4·1/2CH 3 CN) have been synthesized by various methods including Si – C bond cleavage reactions. The crystal structures of 2 • CH 3 CN and 4 · 1/2 CH 3 CN have been determined. 1,2 • CH 3 CN, 3 and 4 · 1/2 CH 3 CN have also been characterized by solution-state ( 1 H, 13 C, 29 Si) and solid-state NMR spectroscopy ( 29 Si CP/MAS). The pentacoordinate silicon atoms of the zwitterions 1-4 are surrounded by four oxygen atoms and one carbon atom. In the crystal, the coordination polyhedra around the silicon atoms of 2 • CH 3 CN (two crystallographically independent zwitterions and two crystallographically independent acetonitrile molecules) can be described as nearly ideal trigonal bipyramids, with the carbon atoms occupying equatorial sites. The crystal structure of 2 • CH 3 CN is considerably influenced by intermolecular N – H···N hydrogen bonds between the zwitterions and the acetonitrile molecules. The coordination polyhedron observed for the silicon atom in the crystal of 4 · 1/2 CH 3 CN can be described as a distorted square pyramid, with the carbon atom in the apical position. The crystal structure of 4 · 1/2 CH 3 CN is considerably governed by intermolecular N –H···O hydrogen bonds between the zwitterions which form infinite chains in the crystal. The 29 Si chemical shifts (δ = – 75,5 to – 85,8) observed for 1,2 • CH 3 CN, 3 and 4 · 1/2 CH 3 CN in solution ([D 6 ]DMSO) and in the crystal are typical of pentacoordinate silicon of the type SiO 4 C. For all compounds very similar 29 Si chemical shifts have been observed for the solution and solid state [⊿(δ 29 Si) ≤ 0,9] indicating that the zwitterions 1-4 do also exist in solution.
Type of Medium:
Online Resource
ISSN:
1865-7117
,
0932-0776
DOI:
10.1515/znb-1993-1201
Language:
English
Publisher:
Walter de Gruyter GmbH
Publication Date:
1993
detail.hit.zdb_id:
2078109-X
detail.hit.zdb_id:
124635-5
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