A combined theoretical and experimental study has been performed to elucidate the structural and dynamical properties of aqueous hexacyanoferrate(II) isolated and in presence of potassium ions. It is shown that in absence of counter ions, the highly negatively charged hexacyanoferrate(II) complex is not stable in aqueous solution.However, if the high negative charge is compensated by potassium counter ions, a stable complex is observed, which is proven by theoretical simulations as well as by EXAFS experiments. From the simulation it is found that potassium ions surrounding the complex are highly mobile and thus, cannot be observed in the experiment. The structure of aqueous hexacyanoferrate(II) in presence of potassium ions is identical to that of the solid state structure, but the mobility of potassium ions is significantly increased in the liquid. These highly mobile potassium ions circulating the complex should be the reason for the very short hydrogen bond lifetimes in the femtosecond range of the cyanide ligands.