COMPLEXATION OF ALKALI-METAL IONS BY THE CRYPTAND 4,7,13,16-TETRAOXA-1,10-DIAZABICYCLO[8.8.5]TRICOSANE, C22C5 - A STRUCTURAL AND EQUILIBRIUM STUDY

The crystal structures of the cryptates formed between 4,7,13,16-tetraoxa-1,10-diazabicyclo[8.8.5]tricosane and three monovalent cations, [M.C22C5]ClO4, have been determined. [H3O.C22C5]ClO4, C17H37ClN2O9, crystallizes in the monoclinic space group P2(1)/n with unit cell dimensions a = 14.166 (2) angstrom, b = 10.955 (2) angstrom, c = 15.007 (1) angstrom, and V = 2286.5 angstrom3 with Z = 4. The structure was refined by a full-matrix least-squares procedure to final R = 0.077 and R(w) = 0.086 for 2006 reflections with I greater-than-or-equal-to 2.5-sigma(I). [K.C22C5]ClO4, C17H34ClKN2O8, crystallizes in the triclinic space group P1BAR with unit cell dimensions a = 13.596 (2) angstrom, b = 15.241 (2) angstrom, c = 11.765 (1) angstrom, alpha = 100.12 (1)-degrees, beta = 98.52 (1)-degrees, gamma = 100.66 (1)-degrees, and V = 2317.1 angstrom3 with Z = 4. The structure was refined by a block-matrix least-squares procedure based on F to final R = 0.045 and R(w) = 0.051 for 3087 reflections with I greater-than-or-equal-to 2.5-sigma(I). [Cs.C22C5]ClO4, C17H34ClCsN2O8, crystallizes in the monoclinic space group P2(1)/n with unit cell dimensions a = 15.666 (4) angstrom, b = 9.535 (2) angstrom, c = 16.335 (4) angstrom, beta = 102.55 (2)-degrees, and V= 2381.7 angstrom3 with Z = 4. The structure was refined by a full-matrix least-squares procedure to final R = 0.037 and R(w) = 0.040 for 2206 reflections with I greater-than-or-equal-to 2.5-sigma(I). In [H3O-C22C5]ClO4, the 0 atom of H3O+ lies 0.666 (3) angstrom above the mean plane of the four C22C5 oxygen atoms. In [K.C22C5]ClO4, K+ lies 0.369 (1) and 0.441 (1) angstrom above the mean plane of the four C22C5 oxygens in the two independent cryptate molecules found in the crystal. In [Cs.C22C5]ClO4, Cs+ lies 1.2996 (3) angstrom above the mean plane of the four C22C5 oxygens, in contrast to the case of [Na.C22C5]ClO4, where Na+ lies 0.011 (2) angstrom below the mean plane of the four C22C5 oxygens. The variation of the apparent stability constant for [M.C22C5]+, K (expressed as log (K/mol dm-3)values), with the nature of M+ in methanol, dimethylformamide, and water, respectively, is 2.30, 2.21, and 2.08 when M+ = Li+; 5.41, 3.66, and 2.58 when M+ = Na+; 5.8, 3.85, and 3.41 when M+ = K+; 5.7, 3.82, and 3.28 when M+ = Rb+; 4.8, 2.90, and 3.31 when M+ = Cs+; 6.48, 5.05, and 4.10 when M+ = Tl+; and 11.13, 9.40, and 9.31 when M+ = Ag+ at 298.2 K. Correlations between these variations in K and cryptate structure with the nature of M+ are sought.