Our understanding of the relationship of gas-phase ion-chemistry and respective chemistry in solution is rather restricted. As a consequence, the utilization of gas-phase results for applications in the condensed phase is currently precluded. Within this PhD project, it is envisaged to gain deeper insights into the relationship of chemistry in these complementary environments.In a first project part, gas-phase C–H-bond activation-reactions mediated by M(II)-methyl complexes (M = Ni, Pd, Pt) have been chosen as highly relevant example processes. The main investigation tools are deuterium-labelling studies combined with mass-spectrometric and NMR-spectroscopic methods. The comparison of the product distributions in solution with already existing gas-phase results will provide insights into the mechanistic similarities and differences in both environments.In a second project part, a detailed and fundamental comparison of reaction pathways in the gas-phase and in solution is envisaged. In this context, it is important that reactions in solution are isothermal, while high-vacuum gas-phase reactions are adiabatic. However, reaction pathways can be described by potential-energy surfaces in both environments. Moreover, in ion-molecule reactions, only the starting compounds and the ionic products of the reaction are known. Neutral reaction products and the ionic intermediates of a reaction can only be elucidated in an indirect manner, for example by deuterium-labelling studies and quantum chemistry. Therefore, postulated gas-phase intermediates will be synthesized and characterized in solution. After the introduction of energy, the product distribution will be compared with the underlying gas-phase reaction. This approach will provide evidence if the synthesized intermediates are part of the reaction pathway and thus directly link gas-phase and solution-phase chemistry.