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Synthesis, Structure, and Properties of Azatriangulenium Salts
Author(s) -
W. Laursen Bo,
C. Krebs Frederik
Publication year - 2001
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20010417)7:8<1773::aid-chem17730>3.0.co;2-f
Subject(s) - chemistry , nucleophilic aromatic substitution , nucleophile , nucleophilic substitution , ion , carbenium ion , crystal structure , nitrogen , computational chemistry , organic chemistry , catalysis
A general synthetic route to novel nitrogen‐bridged heterocyclic carbenium ions of the acridinium and triangulenium type has been developed and investigated. The synthetic method is based on nucleophilic aromatic substitution (S N Ar) on the tris(2,6‐dimethoxyphenyl)carbenium ion ( 1 ) with primary amines and, by virtue of its stepwise and irreversible nature, provides a powerful tool for the preparation of a wide variety of new heterocyclic carbenium salts. Several derivatives of the three new oxygen‐ and/or nitrogen‐bridged triangulenium salts, azadioxa‐ ( 6 ), diazaoxa‐ ( 7 ), and triazatriangulenium ( 4 ), have been synthesized and their physicochemical properties have been investigated. Crystal structures for compounds 2 b‐PF 6 , 2 d‐PF 6 , 4 b‐BF 4 , 4 c‐BF 4 , 6 e‐BF 4 , and 8 are reported. The different packing modes found for the triazatriagulenium salts are discussed in relation to the electrostatic and space‐filling requirements of the ions. The stabilities of the cations 6 a, 7 b , and 4 a , as expressed by their p K R+ values, have been determined in strongly basic non‐aqueous solution by use of the C _ acidity function; the values obtained were 14.5, 19.4, and 23.7, respectively. This study further implied that the C _ scale in its present form is unsuitable for the precise determination of p K R+ values beyond 22.