Effect of a cation on stereochemical activity of lone electron pair in structures of ethylenediaminetetraacetatoantimonates(III), Cat[Sb(Edta)]centerdot xH(2)O [Cat(+) = Cs, NMe4, 1/2(H(2)En), NH4, Tl, K, 1/2Mn, 1/2Cd, or NH3CH2CH2COOH]

The crystal structures of Cs[Sb(Edta)]. H2O (I), NMe4[Sb(Edta)]. 2H(2)O (II ), {H(2)En}[Sb(Edta)](2). 6H(2)O (III), NH4[Sb(Edta)]. H2O (IV), Tl[Sb(Edta )] (V), K[Sb(Edta)]. H2O (VI), Mn[Sb(Edta)](2). 7H(2)O (VII), Cd[Sb(Edta)]( 2). 8H(2)O (VIII), and {HAla}[Sb(Edta)](2) (IX) (where Ala is beta-alanine) were determined by X-ray diffraction. In all the nine structures studied, the coordination number of the antimony atom is six + lone electron pair, a nd the polyhedron of Sb(III) is the psi-pentagonal bipyramid. In compounds I and II, the lone electron pair is situated apically, and, in III-IX, it o ccupies the equatorial position. In the latter case, the volume filled by t he lone electron pair is smaller than that in the former case. The position of the lone electron pair depends on the composition of the complexonate, namely, the polarizing power of the cation and the presence of crystallizat ion water molecules. The weaker the effect of the counterion on the anionic complex, the larger the volume occupied by the lone electron pair.