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)Å and Z= 2. The structure was refined to R= 0.071 for 1 595 reflections.