In this thesis, new aspects of the chemistry of Cp^Ru complexes are described (Cp^=η5-1-methoxy-2,4-tert-butyl-3-neopentylcyclopentadienyl).Despite many similarities with CpRu and Cp*Ru compounds, Cp^Ru complexes display a unique reactivity because of the sterically very demanding Cp^ ligand. This feature prompted further research in this field, and new synthetic and catalytic applications have been developed. Investigations in the context of the ruthenium-catalysed azide-alkyne cycloaddition reaction led to the discovery of a new catalytic application of [Cp^RuCl2]2. It was found that this complex promoted the decomposition of benzylic azides into useful synthetic products.The mechanism of the transformation was studied,and the isolation of several new Cp^Ru complexes enabled further understanding. New Cp^Ru complexes have been prepared and characterised. Different co-ligands were introduced including a bridging alkylidene, an orthometallated phosphine, an imido as well as triflates and carbonyls. It is worth noting that for several of the new Cp^Ru complexes,no analogue with other cyclopentadienyl ligands has been reported. In the final part of this work, investigations about sequential atom-transfer radical addition/dehalogenation reactions are presented. A synthetic process was developed that allows the preparation of trifluoromethyl-substituted cyclopropanes. This method represents an alternative to metal-catalysed cyclopropanations involving problematic diazocompounds.