Comparison of μ2-scaled Hückel theory and Hartree-Fock theory of boranes and carboranes

Roger Rousseau, Stephen Lee

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

The μ2-scaled Hückel method is used to calculate the electronic energy surfaces of the four boranes BnHn 2- (n=8-11) and the carborane C2B8H 10 2-. These electronic energy surfaces and their minimum energy geometries are directly compared to both the single crystal x-ray determined structures and to Hartree-Fock optimized geometries. Bond distances differ on the average by 0.04 Å between alternate methods. It is shown that μ2-scaled Hückel results may be directly interpreted by analysis of the highest occupied and lowest unoccupied molecular orbitals. Also studied by the μ2-scaled Hückel and Hartree-Fock methods are the isomerization pathways of B8H8 2-, B 11H11 2-, and C2B8H 10 2-. Reaction barriers and transition state geometries found by the two different calculational methods are in fair agreement with each other and known literature values. Using the μ2-scaled Hückel method one can readily deduce that the B8H 8 2- and B11H11 2- isomerizations are Woodward-Hoffmann allowed reactions. In the case of B 8H8 2- this allowed mechanism is contrasted to an alternate Woodward-Hoffmann forbidden pathway. Hartree-Fock calculations on the C2B8H10 2- confirm earlier μ2-scaled Hückel based findings, that a second less stable isomer of C2B8H10 2- exists which, in contradiction to Wade's rules of electron deficient clusters, has a pair of open square faces in the cluster.

Original languageEnglish
Pages (from-to)10753-10765
Number of pages13
JournalJournal of Chemical Physics
Volume101
Issue number12
Publication statusPublished - 1994

Fingerprint

Boranes
carborane
boranes
Isomerization
Interfacial energy
isomerization
surface energy
Geometry
geometry
Molecular orbitals
electronics
Isomers
molecular orbitals
isomers
Single crystals
X rays
Electrons
single crystals
electrons
x rays

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

Cite this

Comparison of μ2-scaled Hückel theory and Hartree-Fock theory of boranes and carboranes. / Rousseau, Roger; Lee, Stephen.

In: Journal of Chemical Physics, Vol. 101, No. 12, 1994, p. 10753-10765.

Research output: Contribution to journalArticle

@article{f8cdbae82487432aadef399b4c523888,
title = "Comparison of μ2-scaled H{\"u}ckel theory and Hartree-Fock theory of boranes and carboranes",
abstract = "The μ2-scaled H{\"u}ckel method is used to calculate the electronic energy surfaces of the four boranes BnHn 2- (n=8-11) and the carborane C2B8H 10 2-. These electronic energy surfaces and their minimum energy geometries are directly compared to both the single crystal x-ray determined structures and to Hartree-Fock optimized geometries. Bond distances differ on the average by 0.04 {\AA} between alternate methods. It is shown that μ2-scaled H{\"u}ckel results may be directly interpreted by analysis of the highest occupied and lowest unoccupied molecular orbitals. Also studied by the μ2-scaled H{\"u}ckel and Hartree-Fock methods are the isomerization pathways of B8H8 2-, B 11H11 2-, and C2B8H 10 2-. Reaction barriers and transition state geometries found by the two different calculational methods are in fair agreement with each other and known literature values. Using the μ2-scaled H{\"u}ckel method one can readily deduce that the B8H 8 2- and B11H11 2- isomerizations are Woodward-Hoffmann allowed reactions. In the case of B 8H8 2- this allowed mechanism is contrasted to an alternate Woodward-Hoffmann forbidden pathway. Hartree-Fock calculations on the C2B8H10 2- confirm earlier μ2-scaled H{\"u}ckel based findings, that a second less stable isomer of C2B8H10 2- exists which, in contradiction to Wade's rules of electron deficient clusters, has a pair of open square faces in the cluster.",
author = "Roger Rousseau and Stephen Lee",
year = "1994",
language = "English",
volume = "101",
pages = "10753--10765",
journal = "Journal of Chemical Physics",
issn = "0021-9606",
publisher = "American Institute of Physics Publising LLC",
number = "12",

}

TY - JOUR

T1 - Comparison of μ2-scaled Hückel theory and Hartree-Fock theory of boranes and carboranes

AU - Rousseau, Roger

AU - Lee, Stephen

PY - 1994

Y1 - 1994

N2 - The μ2-scaled Hückel method is used to calculate the electronic energy surfaces of the four boranes BnHn 2- (n=8-11) and the carborane C2B8H 10 2-. These electronic energy surfaces and their minimum energy geometries are directly compared to both the single crystal x-ray determined structures and to Hartree-Fock optimized geometries. Bond distances differ on the average by 0.04 Å between alternate methods. It is shown that μ2-scaled Hückel results may be directly interpreted by analysis of the highest occupied and lowest unoccupied molecular orbitals. Also studied by the μ2-scaled Hückel and Hartree-Fock methods are the isomerization pathways of B8H8 2-, B 11H11 2-, and C2B8H 10 2-. Reaction barriers and transition state geometries found by the two different calculational methods are in fair agreement with each other and known literature values. Using the μ2-scaled Hückel method one can readily deduce that the B8H 8 2- and B11H11 2- isomerizations are Woodward-Hoffmann allowed reactions. In the case of B 8H8 2- this allowed mechanism is contrasted to an alternate Woodward-Hoffmann forbidden pathway. Hartree-Fock calculations on the C2B8H10 2- confirm earlier μ2-scaled Hückel based findings, that a second less stable isomer of C2B8H10 2- exists which, in contradiction to Wade's rules of electron deficient clusters, has a pair of open square faces in the cluster.

AB - The μ2-scaled Hückel method is used to calculate the electronic energy surfaces of the four boranes BnHn 2- (n=8-11) and the carborane C2B8H 10 2-. These electronic energy surfaces and their minimum energy geometries are directly compared to both the single crystal x-ray determined structures and to Hartree-Fock optimized geometries. Bond distances differ on the average by 0.04 Å between alternate methods. It is shown that μ2-scaled Hückel results may be directly interpreted by analysis of the highest occupied and lowest unoccupied molecular orbitals. Also studied by the μ2-scaled Hückel and Hartree-Fock methods are the isomerization pathways of B8H8 2-, B 11H11 2-, and C2B8H 10 2-. Reaction barriers and transition state geometries found by the two different calculational methods are in fair agreement with each other and known literature values. Using the μ2-scaled Hückel method one can readily deduce that the B8H 8 2- and B11H11 2- isomerizations are Woodward-Hoffmann allowed reactions. In the case of B 8H8 2- this allowed mechanism is contrasted to an alternate Woodward-Hoffmann forbidden pathway. Hartree-Fock calculations on the C2B8H10 2- confirm earlier μ2-scaled Hückel based findings, that a second less stable isomer of C2B8H10 2- exists which, in contradiction to Wade's rules of electron deficient clusters, has a pair of open square faces in the cluster.

UR - http://www.scopus.com/inward/record.url?scp=0001016968&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0001016968&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0001016968

VL - 101

SP - 10753

EP - 10765

JO - Journal of Chemical Physics

JF - Journal of Chemical Physics

SN - 0021-9606

IS - 12

ER -