This thesis is mainly concerned with the development of several homogeneously catalyzed carbonylation reactions. In the course of these studies, so-called alternative metal complexes were used in the hydroformylation of olefins with CO and H2. In addition, we investigated the isomerization of olefins. Here, a catalyst system, which transformed α-olefins selectively to β-olefins was developed. Next, it was shown that carbonylation reactions can be performed with liquid formates instead of gaseous CO. This leads to an easily applicable system with broad utilization without the need of expensive high pressure equipment. Furthermore, the generation of the used formate by hydrogenation of CO2 was also investigated. Hence, the overall process makes use of an CO2-equivalent instead of CO derived from the partial burning of coal or hydrocarbons.