The cobalt complexes that we will investigate, trans- and cis-[Co(en)2Cl2]Cl (Figure 1), are both six coordinate. There are six ligands bound to the central metal atom in an octahedral
structure. An octahedron is a geometrical solid with six vertices, each vertex being at 90 degrees to its four nearest neighbors and 180 degrees from the remaining vertex. When viewed as a polyhedron, it can be seen that an octahedron has eight triangular faces. In a perfect octahedron the faces are all identical equilateral triangles. Because we have a mixed ligand set [chloride and ethylenediamine (en), where en is a bidentate ligand that has two metal binding sites], our molecules will have a distorted octahedral structure.