Conformational preferences and reaction mechanisms in organometallic systems. A molecular orbital study

The following work examines the conformational preferences and reaction mechanisms characteristic of real organometallic systems using molecular orbital theory. The first chapter includes a theoretical study of the conformational preferences of the cyclopentadienyl ligand in titanium(III) and titanium(IV) complexes. The approximate method, Partial Retention of Differential Diatomic Overlap (PRDDO), is used to optimize the geometries of Cl;The potential energy surface for the fluxional rearrangement of the cyclopentadienyl ligand in chlorotris(cyclopentadienyl)titanium(IV) is presented in chapter two. PRDDO was used to generate the potential surface for the ;Chapter three explores the reaction mechanism for cis-trans intramolecular isomerization via a nondissociative mechanism for Cr(CO);To compliment the existing methods for determining transition state structures on the potential energy surfaces such as those characterized in this work, a new method is developed which utilizes gradient-based optimizations techniques and is presented in chapter four. The method referred to as Path Coordinate Constrained Geometry Optimization (PCCGO) relies on existing gradient-based techniques for performing geometry optimizations within the ab initio framework. This method proves to be particularly useful in association with the existing force constants methods for locating transition states in extremely complicated systems where transition state geometries are unknown and difficult to guess.;The final chapter in this work is only indirectly related to the scope of this research. For the studies presented here, it is the general practice to optimize and characterize geometries using PRDDO and then determine the corresponding energetics at the ab initio level. Chapter five provides the necessary extended Slater basis sets developed for use at the ab initio level for both the first and second row transition metal series.