Diplomarbeit Base Metal Complexes with PCP Pincer Ligands

Transition metal complexes have received great attention in chemistry due to their ability to catalyze a multitude of reactions. Among the myriads of ligand systems known in literature, pincer ligands, owing to their great stability and reactivity, as well as their excellent modifiability, have shown to be powerful tools in various areas in organometallic chemistry. Pincer ligands are tridentate ligands, that feature a meridional coordination geometry. They consist of an aromatic or aliphatic backbone and two two-electron donor groups, that are connected to the backbone with different linkers such as CH2, NH, NR, O. The oldest class of pincer ligands are PCP pincer ligands, most commonly featuring a benzene backbone and phosphines as electron donor groups. Although presently many PCP complexes with late transition metals are known, only very few such complexes, featuring early transition metals, exist in literature. This is due to the difficulty of creating the s-carbon-metal bond, as generally only noble metals are able to activate C-H bonds. In an attempt to facilitate the formation of s-C-M bonds, this work describes the synthesis of PCP pincer ligands bearing bromine moieties bonded on the ipso carbon of the benzene backbone. The newly generated ligands were shown to effectively form PCP pincer complexes with a wide variety of base metals. Starting from the metal carbonyl complexes, chromium, molybdenum, tungsten as well as manganese, iron and cobalt PCP complexes were successfully synthesized and fully characterized. Nickel PCP complexes were obtained by directly reacting the metal with the ligand in acetonitrile. All compounds were characterized by means of NMR, HRMS and IR spectroscopy as well as single crystal X-ray diffraction.