computational thermodynamic studies of alkali and alkaline earth compounds, olefin metathesis ...

365 Pages·2010·2.18 MB·English

COMPUTATIONAL THERMODYNAMIC STUDIES OF ALKALI AND ALKALINE

EARTH COMPOUNDS, OLEFIN METATHESIS CATALYSTS, AND BORANE ‒ AZOLES

FOR CHEMICAL HYDROGEN STORAGE

by

MONICA VASILIU

A DISSERTATION

Submitted in partial fulfillment of the requirements
for the degree of Doctor of Philosophy
in the Department of Chemistry
in the Graduate School of
The University of Alabama

TUSCALOOSA, ALABAMA

2010
Copyright Monica Vasiliu 2010
ALL RIGHTS RESERVED
ABSTRACT

Geometry parameters, frequencies, heats of formation and bond dissociation energies are
predicted for the alkali (Li, Na and K) hydrides, chlorides, fluorides, hydroxides, and oxides and
alkaline earth (Be, Mg and Ca) fluorides, chlorides, oxides and hydroxides at the coupled cluster
theory [CCSD(T)] level extrapolated to the complete basis set (CBS) limit. The calculations
including core-valence correlation corrections with the aug-cc-pwCVnZ basis sets (n = D, T, Q
and 5) are mostly in excellent agreement with the available experimental measurements.
Additional corrections (scalar relativistic effects, vibrational zero-point energies, and atomic
spin-orbit effects) were necessary to accurately calculate the total atomization energies and heats
of formation. The results resolve a number of issues in the literature.
CCSD(T)/CBS level calculations with additional corrections are used to predict the heats
of formation, adiabatic and diabatic bond dissociation energies (BDEs) and Brønsted acidities
and fluoride affinities for the model Schrock-type metal complexes M(NH)(CRR′)(OH) (M =
2
Cr, Mo, W; CRR′ = CH , CHF, CF ) and MO (OH) transition metal complexes. The
2 2 2 2
metallacyclobutane intermediates formed by addition of C H to M(NH)(CH )(OH) and
2 4 2 2
MO (OH) are investigated at the same level of calculation. The electronegative groups bonded
2 2
to the carbene carbon lead to less stable Schrock-type complexes as compared to the complexes
with a CH substituent. The Schrock compounds with M = Cr are less stable than with M = W or
2
Mo.
The heats of formation and bond dissociation energies (BDEs) for the pyrrole, pyrazole,
imidazole, triazole and tetrazole borane adducts were predicted using an isodesmic approach
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based on G3MP2 calculations. As potential hydrogen storage substrates, dehydrogenation
energies for the elimination of one H molecule were predicted as well as thermodynamic
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properties relative to their acid-base behavior. The H B‒N bonds to an sp2 nitrogen are much
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stronger than those to an sp3 nitrogen for the 5-membered rings. The B‒N BDEs for the
azolylborate adducts are much larger than for the neutral azole borane adducts. The azole
adducts with more number of nitrogens in the ring and with more BH molecules to the azole
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nitrogens are more acidic.

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DEDICATION

To my family, especially to my grandparents, for their infinite love and support
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LIST OF ABBREVIATIONS AND SYMBOLS

aug-cc-pVnZ Augmented, correlation consistent, polarized valence n zeta basis sets,
where n = double (D), triple (T) or quadruple (Q)
aug-cc-pVTZ-DK aug-cc-pVTZ basis sets with all electron DK basis set
aug-cc-pVnZ-PP aug-cc-pVnZ basis sets with pseudopotentials for heavy atoms
aug-cc-pwCVnZ Augmented, correlation consistent, polarized weighted core-valence n
(D, T, Q or 5) zeta basis sets
aug-cc-pwCVTZ-DK aug-cc-pwCVTZ basis sets with all electron DK basis set
aug-cc-pwCVTZ-PP aug-cc-pwCVTZ basis set with pseudopotentials for heavy atoms
awCVTZ aug-cc-pwCVTZ basis sets
B3LYP Becke 93 (exchange), Lee-Yang-Parr (correlation) DFT functional
BLYP Becke 88 (exchange), Lee-Yang-Parr (correlation) DFT functional
BDE Bond dissociation energy
BP86 Becke 88 (exchange), Perdew 86 (correlation) DFT functional
CBS Complete basis set
CCSD(T) Coupled cluster singles, doubles, and disconnected triples
COSMO Conductor-like screening model
CI Configuration interaction
CISD Configuration interaction singles and doubles
CV Core valence
DFT Density functional theory
DK Douglas-Kroll-Hess
DZVP DFT optimized double zeta valence basis set with polarization functions
(except H)
DZVP2 DFT optimized double zeta valence basis set with polarization functions
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ΣD (ΣD ) Total atomization energy
0 0,0K
G3MP2 Gaussian-3 theory calculation using 2nd order Møller Plesset
perturbation theory (MP2)
∆E Complete basis set energy change
CBS
∆E Core valence energy change
CV
∆E Scalar relativistic energy change
Rel
∆E Spin orbit energy change
SO
∆E Scalar relativistic correction calculated as the MVD expectation values
SR
∆E Zero point energy change
ZPE
∆E /∆E BDE at 0 K/298 K
0K 298K
ECP Effective core potential
FA Fluoride affinity
∆G Aqueous deprotonation Gibbs free energy (solution free energy)
aq
∆G Gas phase free energy
gas
∆∆G Aqueous solvation free energy
solv
∆G Gas phase Gibbs acidity
298K
GIAO Gauge independent atomic orbital approximation
∆H Gas phase enthalpy acidity
298K
HA Hydride affinity
HF Hartee-Fock
∆H Heat of formation at 0K
f,0K
∆H Heat of formation at 298K
f,298K
∆H Reaction enthalpy change
rxn
IR Infrared spectrscopy
MO Molecular orbital
MP2 2nd order Møller-Plesset perturbation theory
MVD Mass-velocity and Darwin operators
NIST-JANAF National Institute of Standards and Technology - Joint Army-Navy-Air
Force
NMR Nuclear magnetic resonance
PA Proton affinity
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PBE Perdew-Burke-Ernzerhof (exchange), Perdew-Burke-Ernzerhof
(correlation) DFT functional
PES Potential energy surface
pK Negative logarithm of the acid dissociation constant
a
PP Pseudopetential
PW91 Perdew-Wang 91 (exchange), Perdew-Wang 91 (correlation) DFT
functional
R Gas constant
ROHF Open-shell HF
R/UCCSD(T) Open-shell CCSD(T)
SCF Self consistent field
SCRF self consistent reaction field
SO Spin orbit
SP Square pyramidal
SR Scalar relativistic
T Temperature
TAE Total atomization energy
TBP Trigonal bipyramidal
TZ2P Triple zeta basis set with 2 polarization functions
VTZP Valence high triple zeta basis set with polarized function
ZORA Zeroth order regular approximation to the Dirac equation
ZPE Zero point energy
> Greater than
< Less than
= Equal to
Å Angstrom
° Degrees
± Plus or minus

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ACKNOWLEDGMENTS

I am pleased to have this opportunity to thank all those people who have guided, inspired
and helped me during the years I spent at The University of Alabama. First of all, I am most
indebted to my research advisor Dr. David A. Dixon for his tremendous support, constant
guidance, endless patience and encouragement. He was always there to help and I am so
fortunate to have the opportunity to work with him and to be part of his research group. I would
like to thank Dr. Anthony J. Arduengo, III for being my research advisor for the time I spent in
his group which allowed me to develop laboratory skills. He is a great scientist and his strive for
perfection has been an inspiration for me.
Special thanks to my committee members past and present, Dr. Joseph S. Thrasher, Dr.
Martin G. Bakker, Dr. Masaaki Yoshifuji and Dr. Michael P. Jennings for their important
contribution to my education at UA. I want to thank Dr. Owen W. Webster and Dr. Kevin H.
Shaughnessy for their helpful discussions and valuable advices.
I would like to thank all of the contributors to this work: Dr. Kirk A. Peterson and Dr.
David Feller from Washington State University, Dr. James L. Gole from Georgia Institute of
Technology and Dr. Shenggang Li, The University of Alabama, co-authors of Chapters 2 and 3;
and Dr. Anthony J. Arduengo, III co-author of Chapters 4 and 5.
Many thanks to the Dixon and Arduengo past and present group members, the best
colleagues anyone could ask for, especially Dr. Shenggang Li for his great help, time and
patience when I needed.
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The financial support made my study possible at the University of Alabama and I would
like to thank the Department of Chemistry for its assistantships and DOE for providing the
funding.
Last, but not least, I wish to thank my family and Ami for their love, support and
understanding throughout my PhD years.

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