The main target of this thesis is to gain a deeper understanding of the reduction chemistry of group 16 elements (sulfur, selenium and tellurium) and their derivatives by using divalent lanthanide reagents as reduction agents. Different from cyclopentadienyl counterparts reported by Evans, the employed formidinate lanthanides in this work are supported by a sterically more demanding ligand and the reactivity of these complexes has been discussed by Junk and Deacon and proved by previous work of Roesky et al. The initial target of this project is the reduction of elemental chalcogens by [(DippForm)2Ln(THF)2]. Nano-sized selenium and tellurium were prepared considering the poor solubility of them. As part of the major focus, it is also interesting to study the reduction of diphenyldichalcogenides Ph2E2 (E = S, Se, Te) and perfluorinated diphenyldiselenides (4-RC6H4Se)2 (R = F, OMe) in order to determine whether this reaction can be used for the synthesis of a broad class of such compounds. Moreover, based on the previous study on lanthanides, it is also of interest to extend such reduction chemistry to transition metal complexes. However, as a minor target of this project and also a very initial study, such extension limits only to [(DippNafnaf)Fe(C7H8)] (DippNafnaf = CH[CHN]2). Due to the high reactivity of FeI complex and interesting application potentials of ¿-diketiminato ligand supported iron chalcogenides, the reaction between [(DippNafnaf)Fe(toluene)] and elemental chalcogens has the potential to give some interesting results and thus was studied.