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Increased‐Valence Structures for Qualitative Valence‐Bond Representations of Electronic Structure for Electron‐Rich Molecules
Author(s) -
Harcourt Richard D.
Publication year - 2000
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/1099-0682(200009)2000:9<1901::aid-ejic1901>3.0.co;2-n
Subject(s) - chemistry , valence (chemistry) , generalized valence bond , modern valence bond theory , valence electron , valence bond theory , electronic structure , molecule , chemical physics , electron , crystallography , computational chemistry , molecular physics , quantum mechanics , molecular orbital , physics , organic chemistry
Whereas familiar Lewis‐type valence‐bond structures for singlet‐spin systems involve electron‐pair bonds and lone‐pairs of electrons, increased‐valence structures involve one‐electron bonds and fractional electron‐pair bonds. An increased‐valence structure may be easily derived from a familiar Lewis structure via one‐electron delocalizations of lone‐pair electrons into two‐centre bonding molecular orbitals. The increased‐valence structure is equivalent to resonance between several Lewis structures, including the familiar Lewis structure from which it was derived, and therefore it is more stable than the latter structure. Some of the properties of increased‐valence structures, and their associated Pauling three‐electron bonds as diatomic components of these structures, are discussed, with specific reference to N 2 O and the Fe II O 2 linkages of oxyhaemoglobin. Applications to numerous other systems that involve 4‐electron 3‐centre, 6‐electron 4‐centre, and 6‐electron 5‐centre bonding units are presented. Brief consideration is also given to a speculative Bohr approach to electronic structure.