Multiweek Experiments for an Inorganic Chemistry Laboratory Course: Synthesis of Nickel Complexes Supported by a Tetradentate Ligand with an N2O2 Donor Set

Inorganic Chemistry teaches students the concept that modifications to ligand structures, especially the donor properties, can have a drastic impact on the reactivity and stability of the metal complexes. Experiments described here reinforce this concept through the investigation of two tetradentate ligands derived from o-phenylenediamine and salicylaldehyde. The Schiff base ligand, H2salophen, reacts with Ni(OAc)2•4H2O to yield a maroon colored, square planar complex, Ni(salophen). Under the same conditions, the amine-type ligand, H2salophan, forms a light-blue compound with a formula Ni(salophan)(HOAc). Complex Ni(salophan) free of acetate may be produced from the reaction of H2salophan with Ni(OAc)2•4H2O in the presence of NaOH, but undergoes ligand dehydrogenation to yield Ni(salophen). Students conducting these experiments have the opportunity to learn synthetic techniques and various characterization methods. Most importantly, the inquiry-guided experimental design helps them develop critical thinking skills and apply acquired knowledge to solving a research problem in a laboratory course.