Binding energies and stabilities of potassium ion complexes with ethylene diamine and dimethoxyethane (glyme) from measurements of the complexing equilibria in the gas phase

The temperature dependence of the gas phase equilibria [Formula: see text] where en = ethylene diamine were measured for n = 1 to n = 3. The equilibrium K +  + dimethoxyethane [Formula: see text] K + (dimethoxyethane) was also determined. The measurements were made with a high ion source pressure mass spectrometer equipped with a thermionic potassium ion emitter. The resulting ΔH 0 , ΔG 0 , and ΔS 0 values are compared with the corresponding values for monodentate ligands like H 2 O, NH 3 , CH 3 OCH 3 etc. determined in earlier work. As expected, the bidentate ligands lead to considerably stronger (0,1) interactions. Dimethoxyethane leads to a stronger complex than ethylene diamine. The third molecule of ethylene diamine leads to much weaker binding than is observed for the first two molecules. Explanation of the observed effects is given on basis of electrostatic and steric arguments.