Synthesis, stability and structure of the complex of bismuth(III) with the nitrogen-donor macrocycle 1,4,7,10-tetraazacyclododecane. The role of the lone pair on bismuth(III) and lead(II) in determining co-ordination geometry

Publisher Website
Google Scholar
Abstract
The complex [Bi(cyclen)(H 2 O)(ClO 4 ) 3 ] (cyclen = 1,4,7,10-tetraazacyclododecane) has been synthesized and its crystal structure determined. The Bi has square-antiprismatic co-ordination to the four nitrogens of cyclen (mean Bi–N 2.39 Å) with the upper square being provided by one oxygen from each of the three perchlorates and a water molecule (mean Bi–O 2.77 Å). The formation constant (log K 1 ) of Bi III with cyclen has been determined as 23.45 at I = 0.5 mol dm -3 and 25 °C by differential pulse polarography in an out-of-cell technique, where equilibration was slow and required 6 months. This is a high log K 1 value for a complex with cyclen, in accord with predictions made of the high affinity that Bi III would have for polyamines on the basis of a model of acid–base interactions in aqueous solution. The structures of some complexes of Bi III and the isoelectronic Pb II were analysed in terms of the effect that the lone pair of electrons has on the M–L bond length (M = Bi or Pb, L = ligand donor atom). A relationship was found between the M–L bond length and the distance of L from the lone pair as quantified by the l.p.–M–L (l.p. = lone pair) angle, with M–L decreasing as l.p.–M–L increases. This observation is rationalized in terms of an analogy with the linear co-ordination geometry found in many complexes of Hg II , where the lone pair on Bi III or Pb II occupies one of the two co-ordination sites in the analogous linear two-co-ordinate mercury(II) complex.
Keywords

This publication has 0 references indexed in Scilit: