Crown ether complexes exhibiting unusual 1:2 macrocycle salt ratios: X-ray crystal structures of cyclohexano-15-crown-5•2LiOPh, cyclohexano-15-crown-5•2NaOPh, and 15-crown-5•2NaOPh

Abstract

The crystal structures of three crown ether complexes (cyclohexano-15•crown-5•2LiOPh (1): Li2O7C26H36, Mr = 474.45, λ(CuKα)filt. = 1.5418 Å; cyclohexano-15-crown-5•2NaOPh (2): Na2O7C26H36, Mr = 504.54, λ(CuKα)filt. = 1.5418 Å; and 15-crown-5•2NaOPh (3): Na2O7C22H30, Mr = 452.46, λ(CuKα)mono. = 1.5418 Å) have been determined by X-ray diffraction at room temperature (T = 298 K). Complex 1 crystallizes in space group P21/n with a = 15.032(5), b = 13.332(2), c = 13.533(3) Å, β = 106.28(2)°, V = 2603.2 Å3, and Z = 4. Complex 2 crystallizes in space group P21/n with a = 15.94(1), b = 12.194(7), c = 14.068(7) Å, β = 102.84(5)°, V = 2666.3 Å3, and Z = 4. Complex 3 crystallizes in space group P21/c with a = 12.451(3), b = 17.263(3), c = 12.659(6) Å, β = 115.74(3)°, V = 2450.8 Å3, and Z = 4. The three structures were solved by direct methods and refined by full-matrix least-squares calculations to residuals, R, of 0.080, 0.069, and 0.081 for complexes 1, 2, and 3, respectively. In each structure the macrocycle forms a 1:2 host–guest complex with the alkali metal. Each structure exhibits a dimer of the general form (MAC•2MOPh)2 where M = Li+ and Na+ for structures 1 and 2, respectively, and MAC = cyclohexano-15-crown-5, while M = Na+ and MAC = 15-crown-5 for structure 3. In each case the two metals of the monomeric unit have different crystallographic and chemical environments. In structures 1 and 3 one alkali metal is coordinated to all five oxygens of the macrocycle and to one of the phenoxide oxygens, while the other alkali metal is coordinated to only one oxygen of the macrocycle and to three phenoxide oxygens. In structure 2, one alkali metal is coordinated to only four of the five oxygens of the macrocycle and to two of the phenoxide oxygens, while the other alkali metal is coordinated to only one oxygen of the macrocycle and to three phenoxide oxygens (as in 1 and 3). Key words: crown ether, host–guest complexes, X-ray crystallography.