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Metastable decay rates of alpha-cyclodextrin and maltohexaose coordinated to proton and alkali metal ions were determined from ions produced by liquid secondary ion mass spectrometry in an external source Fourier transform mass spectrometry instrument. For both oligosaccharide compounds the decay rates of the protonated species are faster than any alkali metal coordinated species. Decay rates of the metal cationized species decrease in the order Li+, Na+, K+, and Cs+. The anion of alpha-cyclodextrin has the slowest measurable decomposition rate. The relationships between cation affinities and rates are explored.

483present. This is consistent with the longer S-N bonds to these two nitrogens.One of the most striking features in 7 is the short S--0 "nonbonded" distance of 2.55 A. Although this distance is clearly much longer than a nominal S-0 bond distance of 1.70 A (sum of covalent radii), it is clearly much shorter than the sum of the van der Waals radii of (3.25 A).37 There is, then, a reasonably strong interaction between the S+ and the 0, probably an electrostatic polarization of the oxygen lone pairs by the cationic sulfur. Since the S-N bonds do not have significant multiple-bond character, the lone pairs on oxygen can also interact with the vacant d orbitals on the S+ further strengthening the S-0 interaction. It is probably this s-0 interaction that is strongly perturbing the conformation of the eight-membered ring and perhaps the conformations a t the nitrogens. The short S--0 distance is only 0.20 A longer than the strong S-0 interaction in 1738 and is reminiscent of the bonding observed by Verkade and coworkers in compounds like 18.39 A similar long S-0 bond 19 Registry No. tris(dimethy1amino)sulfonium trimethyldifluorosiliconate, 5921 8-87-0. Supplementary Material Available: Positional parameters, temperature factors, bond distances and angles, and labeled structures (27 pages); structure factor tables (14 pages). Ordering information is given on any current masthead page. (39) (a) Clardy, J. C.; Milbrath, D. S.; Springer, J. P.; Verkade, J. G .Abstract: The dimensionality of the basicity-dependent behavior in the condensed phase, of nonprotogenic organic molecules commonly used as solvents, is approached by a principal component analysis (PCA) of a set of basicity-dependent properties (BDPs) related to hydrogen bonding, proton transfer, and interactions with hard and soft Lewis acids, including the recent -AHoBP3 basicity scale ( J . Phys. Chem. 1985Chem. , 89, 1296Chem. -1304. By use of the Information theory, the original set of 10 thermodynamic and spectroscopic BDPs was reduced to the 5 most informative scales. This in turn allowed the inclusion of more solvents (22) representing the main classes of nonprotogenic organic media. The first two factors obtained by PCA account for about 95% of the total variance of the data. A physical significance is given to these factors by correlating them with intrinsic gas-phase affinities toward the proton and the potassium ion. A blend of electrostatic and charge-transfer or electron-delocalization characters is attributed to the first factor, which is colinear with proton affinity corrected for enhanced-polarizability effect. The correlation observed between the second factor and the potassium-ion affinity corresponds to an essentially electrostatic character. The third factor, of marginal importance, arises in part from the steric hindrance of complexation (front strain). The relationships between dissimilar BDPs are unraveled in terms of the differences between the sensitivities of the properties to the electrostatic, or long-range, and charge-transfer, or shor...

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