A brief overview is presented of the ionic reactions that occur in interstellar gas clouds which lead to the production of the complex molecules determined in those regions. It is shown that the interstellar clouds are weakly ionized plasmas and that the chemistry is largely plasma chemistry involving sequences of ion-molecule reactions producing polyatomic ions which then undergo dissociative recombination with electrons resulting in the observed complex neutral molecules. Whilst many normal biomolecular reactions are involved, another class of reactions, radiative association or 'cold fusion' reactions, are also very important in the overall chemistry. These 'cold fusion' reaction are biomolecular association reactions of ions with molecules followed by emission of radiation which stabilizes the coalesced ion against decomposition back to the reactants. They uniquely occur in the low density, low temperature plasma which are the interstellar clouds, and are very involved in the synthesis of interstellar molecules.