Co-ordination of alkali metals by open-chain polyethers in transition-metal complexes. Part 2. An explanation for alkali-metal selectivity from the X-ray and molecular structure of tetrakis[1-(o-carboxymethoxyphenoxy)-2-(o-hydroxyphenoxy)ethanato(1–)]dirubidiumcobalt(II) and comparison with the dipotassium analogue

Abstract

The synthesis and X-ray crystal structure of the title compound [Co(L2Rb)2], containing the tifunctional centre Rb–Co–Rb, is reported and compared with the analogous [Co(L2K)2] structure. The selectivity of the moiety [CoL4]2– between alkali metals and, in particular, for potassium is discussed on the basis of this comparison. Crystals of [Co(L2Rb)2] are triclinic, a= 14.352(4), b= 14.911(3), c= 16.772(3), α= 93.16(2), β= 106.75(2), γ= 110.91(2)°, and Z= 2. The structure was refined to R= 0.055 for 3 585 reflections.