Stability and structure in solution of potassium and barium complexes with N,N′-diaryldiaza-18-crown-6:: Crystal structure of N,N′-bis(4-dimethylaminophenyl)diaza-18-crown-6 and its complex with barium perchlorate

It has been shown that N,N'-diaryldiaza-18-crown-6 ethers with p-dimethylamino-and p-methoxy groups in the benzene ring (aryl is 4-Mc(2)NC(6)H(4)) (I) and 4-MeOC6H4 (II) form complexes with potassium and barium salts. The influence of these salts on the UV and H-1 NMR spectra of crown ethers I and II has been studied. The stability constants (log beta) of the complexes increase in the series II center dot Ba(ClO4)(2) (2.0), I center dot Ba(ClO4)(2) (2.3), II center dot KBr (2.8), I center dot KBr (3.0). N,N'-bis(4-dimethylphenylamine)diaza-18-crown-6 (L, I) and its complex with barium perchlorate Ba(ClO4)(2) center dot L (III) are characterized by X-ray crystallography. The crystals of I are monoclinic: a = 13.778(2) angstrom, b = 5.9731(9) angstrom, c = 17.542(3) angstrom, beta = 106.65(1)degrees, V = 1383.1(4) angstrom(3), Z = 2, space group P2(1)/n, R = 0.0374 for 990 reflections with 1 > 2 sigma(I). The crystals of III are monoclinic: a = 17.275(4) angstrom, b = 8.017(2) angstrom, c = 26.935(4) angstrom, beta = 100.47(2)degrees, V = 3669(1) angstrom(3), Z = 4, space group C2/c, R = 0.0320 for 1897 reflections with 11 > 2 sigma(I). The molecules of I and III are centrosymmetric. In III, the Ba atom is in the center of substituted diaza-18-crown-6 (DA18C6). The Ba atom is coordinated by all six donor atoms of diaza-18-crown-6 (av. Ba-O, 2.779(3) angstrom; Ba-N, 3.004(4) angstrom) and four oxygen atoms of two asymmetrically bound perchlorate groups (Ba-O, 2.832(4) and 3.031(4) angstrom) arranged below and above the plane of substituted diaza-18-crown-6. The conformations of the macrocycle in free and coordinated L are different.