Co-ordination of alkali metals by open-chain polyethers in transition metal complexes. Part 4. Variation in alkali-metal ion selectivity in cobalt and zinc complexes of 1-(o-carboxymethoxyphenoxy)-2-(o-hydroxyphenoxy)ethane (HL) and the X-ray and molecular structure of [Zn(NH4L2)2

Abstract

The syntheses of complexes of the title ligand [Zn(ML2)2](M = K, Rb, or NH4) are described. The X-ray structure of [Zn(NH4L2)2] is compared with those of [Co(ML2)2](M = K or Rb), and the importance of the hydrogen-bonded dimer L2 in the chemistry of HL is discussed. Subtle changes in M′ of [M′(ML2)2] give large changes in the selective binding of the alkali metal M. Crystals of [Zn(NH4L2)2]are orthorhombic, space group Pncb, with a= 14.046(7), b= 14.577(5), c= 16.691(11)A and Z= 2. The structure was refined to R= 0.071 for 1 595 reflections.