CATION-ETHER COMPLEXES IN THE GAS-PHASE - BOND-DISSOCIATION ENERGIES OF M-ETHER)(X), X = 1-3, M+(1,2-DIMETHOXYETHANE)(X), X = 1 AND 2, AND M+(12-CROWN-4) WHERE M = RB AND CS((DIMETHYL)

Bond dissociation energies of M+[O(CH3)(2)](x), x=1-3; M+[(CH2OCH3)(2) ](x), x=1 and 2; and M+[c-(C2H4O)(4)], where M=Rb and Cs are reported. The bond dissociation energies (BDEs) are determined experimentally b y analysis of the thresholds for collision-induced dissociation of the cation-ether complexes by xenon (measured using guided ion beam mass spectrometry). In all cases, the primary dissociation channel observed experimentally is endothermic loss of one ligand molecule. The cross section thresholds are interpreted to yield 0 and 298 K BDEs after acc ounting for the effects of multiple ion-molecule collisions, internal energy of the complexes, and unimolecular decay rates. The experimenta lly determined BDEs for the monodentate ligand complexes are in good a greement with conventional ideas of electrostatic ligation of gas-phas e ions and with recent ab initio calculations by Feller et al. (averag e discrepancy of 5 +/- 6 kJ/mol). The experimentally determined BDEs f or the multidentate ligand complexes do not agree well with convention al ideas of electrostatic ligation of gas-phase ions or with recent ab initio calculations by Feller et al. (average discrepancy of 15 +/- 5 kJ/mol per metal oxygen interaction). The presence of multiple confor mers of the multidentate ligand complexes in the experimental apparatu s is the likely cause of these large discrepancies.