The thermodynamic and kinetic behaviors of Mg(2+)-F(-) ion pairing in aqueous solution are investigated theoretically and experimentally and are contrasted to those of Ca(2+)-F(-). Thermodynamically, similar to CaF(x)(H(2)O)(14)(2-x) (x = 1 and 2), MgF(H(2)O)(y)(+) (y = 14-20) contact ion pairs (CIPs) are more stable than their solvent-shared ion pairs (SSIPs), whereas the CIPs and SSIPs of MF(2)(H(2)O)(y) are almost isoenergetic. However, in kinetics, the conversion of SSIPs to CIPs for M(2+)-F(-) (M = Mg(2+) and Ca(2+)) ion pairing must overcome a high energy barrier due to the strong hydrat...
