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Supplementary Material Available: Anisotropic temperature parameters, the positional and isotropic temperature parameters of the hydrogen atoms, tables of bond distances, bond angles, and torsion angles (partially) in comparison with values of compound Id, and a description of the crystal packing together with a stereoscopic representation (4 pages). Ordering information is given on any current masthead page. The lists of observed and calculated structure factors are available from A. Gieren.

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We have recently reported the syntheses and certain binding properties of a class of molecules we call "lariat ethers".2"4 These compounds are characterized by a macrocyclic polyether ring and a flexible arm extending from the cycle to which are attached electron donor groups. Those compounds having arms joined by a methyleneoxy group appear to be relatively inflexible and exhibit both relatively weak and solvent-dependent cation binding.2•3 In contrast, when the secondary donor arm is attached to a nitrogen pivot rather than at carbon, binding constants are found to be substantially increased over simple monocyclic systems.4 We now wish to report three important findings regarding the cation binding of the highly flexible nitrogen lariat systems. First, the expected ring size-cation diameter correlation does not appear to be as significant for these cases as for others.5 Rather, binding constants reflect the total number of oxygens present both in the ring and the side arm and seem little affected by the presence of endocyclic nitrogen. Second, the Na+ binding constants peak when

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