Acta Crystallographica Section C

Crystal Structure Communications

Volume 64, Part 3 (March 2008)

metal-organic compounds

sk3189 scheme

Acta Cryst. (2008). C64, m127-m133 [ doi:10.1107/S0108270108002527 ]

Dihydroxyacetone (DHA) monomer complexes with CaBr₂ and CdCl₂

K. Slepokura and T. Lis

Abstract: Two hydrated complexes of monomeric dihydroxyacetone (DHA; the simplest ketose), viz. the calcium bromide complex bis( [mu] -dihydroxyacetone)bis[tetraaquacalcium(II)] tetrabromide (isomorphous with the chloride compound reported previously), [Ca₂(C₃H₆O₃)₂(H₂O)₈]Br₄, (2e), and the cadmium chloride complex poly[[bis( [mu] -dihydroxyacetone)bis[bis(dihydroxyacetone)cadmium(II)]] [diaquatetradeca- [mu] -chlorido-dichloridohexacadmium(II)] tetrahydrate], {[Cd₂(C₃H₆O₃)₆][Cd₆Cl₁₆(H₂O)₂]·4H₂O}_n, (2f), are described. The Ca²⁺ or Cd²⁺ ions are bridged by the carbonyl O atoms from two DHA molecules to form centrosymmetric dimers, with CaCa distances of 4.334 (2) and 4.300 (2) Å in (2e), and a CdCd distance of 4.195 (1) Å in (2f). Almost identical in shape, the eight-coordinate polyhedra of the Ca²⁺ and Cd²⁺ ions are composed of 2n O atoms from n DHA molecules [n = 2 in (2e) and n = 4 in (2f)] and are completed by four water molecules in (2e). DHA molecules chelate the cations via both the hydroxyl and carbonyl groups and exist in an extended conformation, with both hydroxyl groups being synperiplanar to the carbonyl O atom. The crystal structures are stabilized by similar extensive O-HX (X = Cl or Br) and O-HO hydrogen-bond networks involving all hydroxyl groups and the water molecules.

Formula: [Ca₂(C₃H₆O₃)₂(H₂O)₈]Br₄ and [Cd₂(C₃H₆O₃)₆][Cd₆Cl₁₆(H₂O)₂]·4H₂O