A study of reaction mechanisms and rearrangements in inorganic, organometallic and solid state chemistry by molecular orbital theory.

Our research group carries out molecular orbital calculations at several levels to investigate static and dynamic properties of discrete compounds, as well as solid state materials. These calculations vary in complexity from the ab initio to extended Hückel levels. There exists a wide variety of analytical methods to view the results from these calculations.

In the molecular area, a common theme that we are exploring is the mechanisms which form carbon-carbon bonds in transition metal complexes. Some examples include the trimerization of acetylene via Ta(OR)₃ and CoCp based catalysts, the acetylene metathesis reaction and the dimerization of butadiene with Ni(O). An example of a step in this catalytic cycle is shown in Figure 1. We also are developing a series of orbital symmetry rules for the coupling of unsaturated ligands coordinated to a metal, electrocyclic ring closure reactions in polyene-ML_n complexes and haptotropic rearrangements. The calculations in our group are arried out at the Hartree-Foch level with some perturbation theory, CASSCF, QCISD or coupled cluster techniques) or more frequently with a hybrid density functional.

In the solid state area, we primarily use tight binding calculations with an extended Hückel type Hamiltonian. We have looked at a number of compounds which are ferroelectric. Our interest here is to derive an electronic rationale for the distortion which occurs upon going to the ferroelectric state, as well as the mechanism for this deformation. Some examples include TlGaSe₂, TlBiTe₂, and the Aurivillius phases. We have also examined the electronic sources of Te-Te bond formation in CuTe, K₂Cu₅Te₅, etc. We also have an ongoing collaboration within the Texas Center for Superconducting at the University of Houston to examine the bonding and mechanisms for superconductivity in new materials. An example of one compound that has been investigated is shown in Figure 2.