Experimental and computational studies of transition metal complexes with polydentate amino- and amidophenolate ligands : synthesis, structure, reactivity and magnetic properties

Abstract

Chelating polydentate ligands play a key role in several areas of modern coordination chemistry. They can be exploited, for example, in catalysis, bioinorganic chemistry, heavy metal abstraction and molecular magnetism. Furthermore, compounds of this type can be found in natural chemicals, commercial products and industrial applications. In this dissertation, several 3d, 4d and 5d transition metal complexes with polydentate amino- and amidophenolate ligands were prepared and their structure, reactivity and magnetic properties were studied with experimental and computational techniques. In the first part of the dissertation, the solid-state structure, reactivity and magnetic properties of 12 novel 3d transition metal complexes were examined. The magnetic behavior of a polynuclear metal complex can be linked to its solid-state structural features to constitute so-called magnetostructural correlations. A clear connection between the M-O-M angles and exchange coupling constants was found in the studied dinuclear Fe(III) complexes. Similar magnetostructural correlations were not equally strong in dinuclear ferromagnetically coupled mixed-valence Mn(II)/Mn(III) system. However, the distortion of the Mn(II) polyhedron from ideal square pyramidal geometry was shown to be related to the strength of the exchange coupling, and together with the M-O-M angle, the nature and strength of the coupling could be estimated. The second part of this work describes the synthesis and behavior of four novel complexes with heavier 4d and 5d transition metals. Two high-valent molybdenum(VI) complexes with non-innocent tetradentate amidophenolate ligand were prepared and thoroughly characterized using a variety of experimental and computational methods. One of the complexes is the first stable molybdenum(VI) amidophenoxide radical. In addition, the versatility of the bidentate aminophenolate ligands was observed in the synthesis of tungsten(VI) complexes which showed unexpected ligand reactivity upon coordination to a metal cation.