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NMR Studies of the Phosphazene/Phosphazane Rearrangement
Author(s) -
Thomas Berthold,
Paasch Silvia,
Böhme Uwe
Publication year - 2005
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.200400394
Subject(s) - phosphazene , chemistry , double bond , crystallography , anisotropy , ring (chemistry) , stereochemistry , physics , quantum mechanics , polymer chemistry , polymer , organic chemistry
In compounds such as hydroxy, methoxy and ethoxycyclophosphazenes a phosphazene/ phosphazane rearrangement occurs. In this process the electronic structure of the PN ring system changes under reduction of the endocyclic double bonds. A decrease of the s bond order of the PN bondings results in a decrease of the scalar couplings 1 J PN and 2 J PP . In addition, considering the solid‐state 31 P NMR spectra, significant differences between the phosphazene and phosphazane forms can be observed caused by a change of the local symmetry at the phosphorus atom. In the case of cyclotriphosphazenes a local C 2v symmetry exists (strictly valid for these compounds only) and the shielding (shift) tensor is characterized by a small anisotropy as well as a small axiality. Contrary to this in phosphazanes the phosphoryl bond is dominating the chemical shift tensor, characterized by a double to triple anisotropy and a high axiality. Quantum chemical GAUSSIAN calculations reflect these differences between phosphazenes and phosphazanes.