This award in the Inorganic, Bioinorganic, and Organometallic Chemistry Program supports research on phosphorus exchange reactions by Dr. Richard L. Keiter of the Chemistry Department, Eastern Illinois University. Kinetic and thermodynamic studies of phosphine exchange in dangling ligand complexes of chromium and molybdenum will be carried out. The study is prompted by the observation that phosphorus ligand exchange in some tungsten complexes is faster than previously assumed. In cases where one dangling phosphine arm of a ligand is capable of associating with a cis carbonyl ligand on the tungsten, the second phosphine arm can displace the coordinated phosphine more readily. This idea will be tested in other metal complexes using a variety of ligand combinations in various solvents. NMR and X-ray crystallographic methods will be employed. The significance of this reaction is that it results in isomerization, that is, structural modification, of the complex and affects subsequent reactivity. While repulsive forces are often taken into account in understanding reactivity, attractive forces often are not. This opens the possibility of controlling substitution rates by employing ligands with dangling groups that have an affinity for other ligands attached to the central metal of the complex.
