Whilst the reactivity of multiply-charged ions is quite well understood in the context of aqueous media and solid phases, relatively little is known of their chemical behaviour in the gas phase. It is only since the 1980's, due mostly to advances in experimental technology, that their role in the chemistry and more recently in biological processes has been revealed. Among such species, metal ion complexes are of great importance in biological function and gas-phase organometallic ion chemistry has witnessed a great development from both the theoretical and the experimental points of view. In gas-phase, the cationization of neutral molecules by metal dications is often accompanied by bond activation effects, which can lead to specific fragmentations. Then, depending on a specific dication attachment site, the establishment of diagnostic ion fragmentations, observed in mass spectrometry experiments, is of potential interest for the structural characterization. In this context, the development of electrospray ionization techniques has indeed opened up the possibility of producing clusters involving metal dications in the gas phase, and the interest in dication-molecule reactivity grew significantly. Studies of reactions involving metal dications and organic bases reveal a clear distinction between alkaline-earth metal and transition metal dications. In the first case, [base-M]2+ complexes could be isolated in the gas phase and their unimolecular reactivity be investigated. For transition metals, it appears that dications are instable and lead to monocations species after the loss of a proton from [base-M]2+. These features will be illustrated in this presentation, through theoretical (DFT calculations) and experimental approaches (mass spectrometry), for complexes involving prototypical biological molecules (urea, amino acids, natural and modified nucleic basis ) and Ca2+, Mg2+, Pb2+, Cu2+, Ni2+ and Co2+ dications.