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Electronic Decomposition Analysis of Substituted Metal Alkene and Alkyne Complexes
ERIKA ISAACSON, DR. JOE SCANLON
Metals used to activate alkenes and alkynes
Within the past decade, research in the potential of gold as a catalyst has increased significantly.
Gold is known for its interactions with carbon‐carbon π bonds.
◦ It activates alkenes and alkynes within reactions.
◦ When using gold as a catalyst with molecules with multiple alkenes or alkynes it is important to know which one will become activated.
Marion, N. et al. Org. Lett. 2007, 9, 2653.
Past results
In the past, Frenking et. al used EDA to determine the nature of the bonding between ligands and metals. ◦ This study looks at how group 11 metals interact with ethyne and ethene .
◦ EDA calculation partition interaction energy into electrostatic, orbital, and Pauli repulsion.
◦ For Au, the interactions were found to be more electrostatic than covalent.
◦ Frenking et al. calculated that ethene has coordination energy six kcal/mol lower than ethyne to Au+.
Frenking, G. et al., J Phys. Chem. A, 2004, 108, 3134
Past results
Previous research in our group examined coordination energies of substituted ethynes and ethenes. ◦ A strong correlation to substituents’ Hammett parameters and energy of coordination.
◦ The more electron donating that a substituent is, the stronger the correlation energy to Au.
◦ Using NBO, it was also found that the π‐type back donation increased for electron withdrawing groups for the species studied.
◦ The present study investigates uses EDA of these complexes to determine why the energy of coordination is decreasing and what other interactions are influencing this.
Past Results
NBO was used to analyze how the orbital contribution to the coordination energy changed upon substitution. ◦ It was found that the orbital interaction energy increased with the electron withdrawing capability of the substituent.
◦ This is opposite of overall trend for energy of coordination.
This research
Uses electronic decomposition analysis to determine electrostatic, orbital, and Pauli repulsion interactions of Au with substituted ethynes and ethenes. ◦ Since we’ve never run these calculations before, we are going to first compare our calculations to interactions of unsubstituted species that was studied by Frenking.
◦ After we are confident in our calculations, we will do calculations of substituted ethynes and ethenes that were previously studied in our group.
Theoretical Methods
GAMESS – General Atomic and Molecular Electronic Structure System was used.
◦ M06 density functional
◦ SDD basis set and ECP for Au ◦ 6‐311+G(2d,p) basis set was used for non‐metal atoms
Sample input file
Geometry of Au(C2H2)+ was taken from the Frenking paper. To get the desired calculations, the input file has to be pieced together.
Frenking, G. et al., J Phys. Chem. A, 2004, 108, 3134
Calculation
Fragments
Atomic Symbol and Number
Sample input file – key components
The type of calculation.
Defining the atoms in the molecule and gold atom. C2H4 is MATOM(1)=6 and gold is MATOM(2)=1, representing the number of atoms in each fragment. This is dependent on the order of the coordinates.
Cartesian coordinates – based on the geometries of Frenking et al. and they are listed in the order of the defined fragments. Basis set, has to be listed under the coordinates for every atom in the molecule.
Cartesian
Coordinates
Basis Set
Calculation
Sample input file – key components
ECP potential calculation of Au – at the end of the input file after the Cartesian coordinates and the basis sets.
Sample Input file
The input file was created through trial and error of calculations since we could not find an example input file that included all the options we wanted.
◦ One space caused our jobs to fail for an entire week.
◦ Error codes were unhelpful.
We struggled for a month and only got two calculations for molecules to complete properly. Comparison
ENERGIES FROM FRENKING PAPER
RAW DATA FROM THIS STUDY FOR AU(C2H2)+
Frenking’s method breaks up the energy interactions in different ways than the GAMESS EDA method.
Frenking, G. et al., J Phys. Chem. A, 2004, 108, 3134
Future work
Standardize a way of creating an input file to minimize failed calculations.
Learn more about the GAMESS EDA method so we can better compare it to Frenkings results.
◦ We need to perform more calculations (Au(C2H4)+) to be able to compare with Frenking.
◦ Although are energy calculations were different than Frenking et. al, as long as trends are consistent we can proceed.
Prepare and execute more input files for substituted ethynes and ethenes.
Compare energies to previous research
Calculate the energies for larger molecules and eventually determine forces what causes selectivity in systems with multiple π‐bonds.
References
Frenking, G., Rayón, V. M., Nechaev, M.S.; Energy Partitioning Analysis of the Bonding in Ethylene and Acetylene Complexes of Group 6, 8, and 11 Metals: (CO)5TM−C2Hx and Cl4TM−C2Hx (TM = Cr, Mo, W), (CO)4TM−C2Hx (TM = Fe, Ru, Os), and TM+−C2Hx (TM = Cu, Ag, Au),, The Journal of Physical Chemistry A 2004 108 (15), 3134‐3142 DOI: 10.1021/jp031185+
Marion, N., Gealageas, R., Nolan, S. P.; [(NHC)AuI]‐Catalyzed Rearrangement of Allylic Acetates; Org. Lett., 2007, 9, 2653‐2656.
Scanlon, J., Steggal, K., Iimura, I.; Substituent Effects on Coordination Energies of Alkenes and Alkynes to Au and Pd Complexes