N₂ fixation and dehydrogenation of methanol and formic acid with late transition metal complexes

The transformation to a society that runs on sustainable energy can be facilitated by new technologies that allow solar energy to fuel conversions. Catalytic processes play a crucial role in such technology. In the introduction Chapter an overview of homogeneous catalysts is given, which are able to store solar energy into chemical energy. In Chapter 2, the formation of salen-based ruthenium complexes is described. The salen complexes are able to dehydrogenate methanol to dihydrogen and carbonate in basic media. Mechanistic investigations show that the carbonyl ligand on one of the salen complexes can react with KOH forming potassium formate, but that the carbonyl-complex is not the active species during the dehydrogenation reaction. Chapter 3 describes the coordination of a tripodal indolyl-phosphine (PP₃) ligand to ruthenium(+II) forming an octahedral Ru(PP₃)Cl₂ complex. This complex can be stepwise reduced to the corresponding rare Ru^I and Ru^ON₂ which in turn can be oxidized back to the stable Ru^II complex by the addition of organochlorides. In Chapter 4 the class of ligands is extended to isomers and electronic variations while coordinated to ruthenium. These complexes are subsequently studied for dinitrogen coordination, dinitrogen reduction, and formic acid decomposition. In the final Chapter, the coordination chemistry of first row transition metals Ni^II, Co^II and Fe^II to the same tripodal ligands is reported. The reduction of these complexes with two electrons shows that the iron complexes can coordinate dinitrogen. Noticeable different activations of the dinitrogen ligand coordinated to the metal atom are observed for the different ligands used.