Novel diiron dichalcogenolato complexes : models for active site of [FeFe] hydrogenase This dissertation focused on the synthesis and characterization of novel model complexes of the [FeFe] hydrogenase active site containing diselenolato ligands. The substitution of one or two carbonyl groups of Fe2( Se2C3H5CH3)(CO)6 by PPh3 P(OMe)3 or dppe were investigated and leads to syntheses of several [FeFe] hydrogenase models containing [2Fe2Se] core. Moreover a series of oxetane containing diiron dichalcogenolato complexes have been prepared. Diiron model complexes containing mixed (S Se) or (S Te) atoms have been also prepared. Diiron Fe2( Se(CH2)xSe )(CO)6 and the tetrairon [Fe2( Se(CH2)ySe )(CO)6]2 model complexes containing selenolato ligands with different length linker (x = 5 6; y = 4 5 were also prepared. The electrochemical properties for the newly compounds have been studied to assess their ability to catalyze electrochemical reduction of protons to give dihydrogen. Furthermore I was gave center of attention on the photoelectron spectroscopy of some compounds. The electronic structure of these complexes is further analyzed with the aid of DFT computations.