Open AccessStructural investigations of phosphorus–nitrogen compounds. 7. Relationships between physical properties, electron densities, reaction mechanisms and hydrogen‐bonding motifs of N 3 P 3 Cl (6 − n ) (NHBu t ) n derivatives
Author(s) -
Bartlett Stewart W.,
Coles Simon J.,
Davies David B.,
Hursthouse Michael B.,
Kiliç Adem,
Shaw Robert A.,
İbişogˇlu Hanife,
Ün İlker
Publication year - 2006
Publication title -
acta crystallographica section b
Language(s) - English
Resource type - Journals
eISSN - 1600-5740
pISSN - 0108-7681
DOI - 10.1107/s0108768106000851
Subject(s) - phosphazene , hydrogen bond , chemistry , ring (chemistry) , crystallography , nucleophilic substitution , nucleophile , crystal structure , stereochemistry , molecule , medicinal chemistry , organic chemistry , catalysis , polymer
A series of compounds of the N 3 P 3 Cl (6 − n ) (NHBu t ) n family (where n = 0, 1, 2, 4 and 6) are presented, and their molecular parameters are related to trends in physical properties, which provides insight into a potential reaction mechanism for nucleophilic substitution. The crystal structures of N 3 P 3 Cl 5 (NHBu t ) and N 3 P 3 Cl 2 (NHBu t ) 4 have been determined at 120 K, and those of N 3 P 3 Cl 6 and N 3 P 3 Cl 4 (NHBu t ) 2 have been redetermined at 120 K. These are compared with the known structure of N 3 P 3 (NHBu t ) 6 studied at 150 K. Trends in molecular parameters [phosphazene ring, P—Cl and P—N(HBu t ) distances, PCl 2 angles, and endo‐ and exocyclic phosphazene ring parameters] across the series are observed. Hydrogen‐bonding motifs are identified, characterized and compared. Both the molecular and the hydrogen‐bonding parameters are related to the electron distribution in bonds and the derived basicities of the cyclophosphazene series of compounds. These findings provide evidence for a proposed mechanism for nucleophilic substitution at a phosphorus site bearing a PCl(NHBu t ) group.