CATION-ETHER COMPLEXES IN THE GAS-PHASE - BOND-DISSOCIATION ENERGIES AND EQUILIBRIUM STRUCTURES OF LI-4([O(CH3)(2)](X), X=1)

Bond dissociation energies, equilibrium structures, and harmonic vibra tional frequencies of Li+[O(CH3)(2)](x), x = 1-4, are reported. The bo nd dissociation energies are determined experimentally by analysis of the thresholds for collision-induced dissociation of the cation-ether complexes by xenon (measured using guided ion beam mass spectrometry) and computationally by ab initio electronic structure calculations at the RHF and MP2 levels of theory. In all cases, the primary and lowest energy dissociation channel observed experimentally is endothermic lo ss of one ether molecule. The cross-section thresholds are interpreted to yield 0 and 298 K bond energies after accounting for the effects o f multiple ion-molecule collisions, internal energy of the complexes, and unimolecular decay rates. The experimental and theoretical bond en ergies are in good agreement with previous experimental results for Li +[O(CH3)(2)]. Agreement between experiment and theory is also good for x = 2-4, where the bond energies calculated with a 6-31+G basis set are larger than the experimental values by 12 +/- 10, 10 +/- 11, and - 2 +/- 14 kJ/mol, respectively. Some of these discrepancies disappear a t the complete basis set Emit. The equilibrium structures are determin ed primarily by strong electrostatic and polarization interactions. Ch arge transfer interactions are also important, Bs indicated by natural energy decomposition analysis of the calculated wave functions.