Structures of the spontaneously resolved six-coordinate potassium chloro-(ethylenediaminetriacetato acetic acid) iron(III) monohydrate and the seven-coordinate potassium (ethylenediaminetetracetato) iron(III) sesquihydrate

摘要

The molecular structure of K[Fe(Hedta)(Cl)].H2O (1, edta=ethylenediaminetetraacetate) has been determined: Triclinic, P (1) over bar (No. 1), Z=1, a=6.735(1), b=7.245(1), c=8.815(2) Angstrom, alpha=72.87(2), beta=85.00(2), gamma=76.30(2)degrees, V=399.3(2) Angstrom(3), R-1=0.0355, wR(2)=0.0968. Compound 1 is the third spontaneously resolved edta-complex containing an uncoordinated, protonated acetate arm. The Deltalambda(E) enantiomorph has been refined during the structure determination. The reasons for this exceptional behavior are discussed in the framework of related transition metal complex structures with monoprotonated edta as a ligand. Important forces behind the formation of optically pure crystals are: the strong Fe-Cl bond and the presence of potassium as a counter ion. Trials to prepare the six-coordinate derivative of 1 by simple deprotonation of the detached acetate arm did not result in the formation of K-2[Fe(edta)(Cl)] but the seven-coordinate salt K[Fe(edta)(H2O)].1.5H(2)O (2) was obtained with the following crystallographic parameters: Monoclinic P2/c (No. 13), Z=4, a=15.287(4), b=7.697(2), c=14.380(3) Angstrom, beta=104.98(2)degrees V=1634.5(7) Angstrom(3), R-1=0.0338, wR(2)=0.0821. (C) 2002 Elsevier Science B.V. All rights reserved. [References: 44]