Structure and Spectroscopy of Oraganometallic Compounds

Dr Charles Kriley of the chemistry department at Grove City College has synthesized a series of novel Ni complexes of the form NiCl2(PRR’R’’)2 and has found that there is uncertainty regarding the ground state geometry.  In particular, the tetrahedral and square planar geometries appear to be quite close in energy and the lowest energy form may depend on the details of the ligand structure.  Recently, we have begun a collaborative effort to provide insight into the situation from electronic structure calculations.  The ultimate goal is to elucidate the factors that favor one geometry over the other and to accurately predict the structures and properties of future compounds.  A first step in this effort is to determine a computational approach that can reliably predict the geometries of these complexes and the relative energies of the various electronic states (especially the different spin states). 

Presently, we using extremely rigorous calculations on a model compound, NiCl2(PH3)2.  While this compound is not stable in the laboratory, it does provide the simplest model compound that can be treated on the computer and retains all the essential features of the target systems.   CCSD geometry optimizations and energies of the lowest energy state of each spin for each geometry will be calculated as benchmarks.  (CCSD is a well known, robust, and accurate computational methodology.)   Less rigorous density functional calculations (referred to as DFT calculations) will be compared to the benchmark results to determine the best basis set and functional to use.  We are also working on larger systems in a similar fashion.  Once a reliable DFT method has been established on the basis of several progressively larger models, it will be applied to the compounds synthesized by Dr. Kriley.

In the future we will calculate the IR and electronic spectra of the molecules and the transition states for transition from one isomer to another and investigate the effect on the structure of the solvent and the effect of being in a crystal.