Phosphate substituted dithiolene complexes as models for the active site of molybdenum dependent oxidoreductases Molybdenum dependent enzymes are involved in essential metabolic transformations in bacteria plants and human beings. The extreme instability of the molybdenum cofactor (Moco) prevents its use as an effective treatment for patients with a Moco deficiency. Therefore the design develop and execute the artificial molybdenum cofactor models are essential. In the present thesis the asymmetric molybdopterin (mpt) model precursors with oxygen functionality and various electronic structures and their Moco model complexes mimicking the natural cofactor have been synthesized and comprehensively investigated through multi nuclear NMR MS IR resonance Raman X ray crystallography UV Vis and electrochemical methods. Notably the asymmetrically substituted dithiolenes in this thesis are confirmed through a significant push pull effect which is tuning its electronic structure. The redox behavior of Moco model complexes was investigated by temperature dependent cyclic voltammetry. Electronic and vibrational spectral studies were investigated in detail to understand substituents effect on the electronic structure of model complexes and to elucidate roles of mpt in catalysis. Since the model complexes can be considered as structural models for the Moco dependent oxidoreductases catalytic oxygen atom transfer (OAT) reactions in DMSO PPh3 were investigated. The main focus of the present thesis was achieved through the development of various synthetic routes that address phosphonate ... Molybdenum Molybdenum Cofactor Molybdopterin OAT Reaction Oxidoreductases Phosphate Substituted Dithiolene