A study of the pyramidality index in tris(2,4,6-triisopropylphenyl)phosphonium perchlorate
Date
2013
Authors
Boeré, René T.
Zhang, Yuankui
Journal Title
Journal ISSN
Volume Title
Publisher
International Union of Crystallography
Abstract
The title compound, C45H70P+ ClO4
or [Tripp3PH+][ClO4
],
was produced from the perchlorate salt of the corresponding
radical cation Tripp3P + through very slow H-atom abstraction
reactions in a solution of 1,2-dimethoxyethane (Tripp is 2,4,6-
triisopropylphenyl). The H atom on the P atom was located in
a difference map and was freely refined with an isotropic
displacement consistent with full occupancy [P—H =
1.37 (3) A ° ]. It is the most sterically congested triarylphosphonium
salt yet to be reported and has a ‘propeller’ arrangement
of the three Tripp groups around the P atom, with the
protonation site located along the molecular threefold axis.
There are short contacts between the flanking isopropyl
methine H atoms and the P atom [P H = 1.99 (2)–
2.17 (2) A ° ]. The sum of the angles around the P atom
[ (C—P—C) = 349.9 (6) ] is a convenient index of pyramidality
for tricoordinate centres. This value is significantly larger
than in analogous Mes3PH+ salts (Mes is mesityl or 2,4,6-
trimethylphenyl), for which the average of the three reported
structures in the literature is (C—P—C) = 345.3 (6) . For
comparison, in the ubiquitous Ph3PH+ salts, this parameter has
a typical average value of only 333.3 (9) . The value of (C—
P—C) in the title compound is midway between that of the
neutral phosphane Tripp3P [334.4 (6) ] and the phosphoniumyl
radical cation Tripp3P + [359.8 (2) ]. This geometrical
feature provides additional support for the assignment as a
phosphonium salt.
Description
Sherpa Romeo green journal
Keywords
Crystal structure , Triarylphosphonium ions , Pyramidality index , Phosphoniumyl radical cations
Citation
Boere, R. T., & Zhang, Y. (2013). A study of the pyramidality index in tris(2,4,6-triisopropylphenyl)phosphonium perchlorate. Acta Crystallographical Section C, Crystal Structure Communications, C69, 1051-1054. doi:10.1107/S0108270113020647