In chapter 2 the systematic complexation of one, two, and three, cyclopentadienyl ligands to lanthanides was examined. The Delta G complexation energy is found to closely follow the summation of the metal's first, second, or third ionization potentials depending on whether it is complexing to one, two, or three cyclopentadienyl rings. Strong back bonding occurs from the cyclopentadienyl rings into the metal's 5d orbitals.In chapter 3 several isomers of CeXOY+ clusters were studied.The global minimum for X=2Y-1 was generally found to have the most symmetric bonding. The global minimum for X=2Y+1 was found to be formed with the addition of O2 to X=2Y-1. O2 gains some superoxide character.In chapter 4 the most complete and accurate computations on the GeSiH2 PES to date were carried out with correlation levels as high as CCSDTQ(P).For the first time the mono bridged structure with a terminal hydrogen on silicon was definitively found to be lower in energy than the vinyl like structure with both hydrogens on silicon, 0.72 kcal/mol.