Multiweek Experiments for an Inorganic Chemistry Laboratory Course: Synthesis of Nickel Complexes Supported by a Tetradentate Ligand with a N_2O_2 Donor Set

摘要

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, H_2 salophen, reacts with Ni(OAc)_2·4H_2O to yield a maroon, square planar complex, Ni(salophen). Under the same conditions, the amine-type ligand, H_2 salophan, forms a light-blue compound analyzed as [Ni(Hsalophan)(OAc)]_2. The Ni(salophan) complex free of acetate may be produced from the reaction of H_2 salophan with Ni(OAc)_2·4H_2O 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.