Premium
The Structure of 2‐Azaallenium Cations
Author(s) -
AlTalib Mahmoud,
Jibril Ibrahim,
Würthwein ErnstUlrich,
Jochims Johannes C.,
Huttner Gottfried
Publication year - 1984
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19841171205
Subject(s) - chemistry , mndo , steric effects , allene , basis set , molecular orbital , nitrogen atom , computational chemistry , ab initio , molecular geometry , crystallography , ab initio quantum chemistry methods , atom (system on chip) , ion , molecule , stereochemistry , density functional theory , organic chemistry , group (periodic table) , catalysis , computer science , embedded system
According to an X ‐ray structural analysis, the 2‐azaallenium hexachloroantimonate 23 crystallizes with the topology of an allene (geometry 1a ) and not of a 2‐azaallyl cation ( 1b ). Ab initio molecular orbital calculations (3–21 G basis set) and semiempirical MNDO calculations for the unsubstituted 2‐azaallenium cation and for some mono‐ and disubstituted derivatives ( 24 ) confirm the experimental results: In many cases the allenium geometry 24a is more stable than the 2‐azaallylium form 24b. Electron‐releasing substituents reduce the energy difference between 24b and 24a. With two amino substituents the allylium geometry 24b is energetically preferred to the allenium form 24a. In general, substituted 2‐azaallenium salts are sterically flexible around the central nitrogen atom. Compound 23 was synthesized by a new method.