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Tuesday, December 6 • 8:20am - 8:40am
QTAIM Study of Bonding in Carboranes

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The bonding of boron atoms in carboranes and metalloboranes has been a subject of interest for scientists for several decades due to the number of atoms in close radial proximity of each other despite the fact that it is considered to be electron deficient possessing only three valence electrons.[1] A three-center-two-electron bond has been hypothesized to explain the boron atom’s ability to form more than three bonds within a molecule and several papers have been written supporting the existence of this bonding arrangement.[10-11] This study utilized computational chemistry techniques including the QTAIM method to obtain the electron densities, the Laplacian scalars, charge values, basin paths, Poincare-Hopf algebra, and specifically, a B3LYP DFT method with an ab initio MP2 level of theory, and a 6-311+G(2d,p) basis set to produce a geometric optimization of C2B5H7 and C2B7H9. The Trans-Ring configuration of C2B5H7 was reported as the most thermodynamically stable configuration. The ring critical point ρ(r) values of the Trans-Ring configuration of C2B5H7 and C2B7H9 were reported as lower than the corresponding bond critical point ρ(r) values to which they are attached, all of which indicate that there is not a three-center-two-electron bond present in the molecule. The charge values and Laplacian scalars results indicate fragment behavior, similar to ligand behavior, between the boron and carbon atoms and their corresponding hydrogens. The results lead to the conclusion that ligand close packing and coordination theories, along with Wade’s Rules, give better explanations for the bonding and behavior of closo-carboranes.


Tuesday December 6, 2016 8:20am - 8:40am PST
014 Zeis Hall