title: Square versus tetrahedral iron clusters with polyoxometalate ligands.
abstract: Two new insoluble transition metal substituted phosphotungstates, (C2N2H10)11[{(B-alpha-PW9O34)Fe3(OH)3}4(PO4)4Fe].38H2O(1) and K4(C2N2H10)12[(alpha-PW10Fe2O39)4].30H2O(2), have been isolated by the hydrothermal reaction of [A-alpha-PW9O34]9-, Fe(III) ions and ethylenediamine. Compound 1 has a tetrahedral symmetry and contains a Fe13 core built from the assembly of four Fe(III) trisubstituted [B-alpha-PW9O34]9- anions around a central disordered iron ion via four phosphato ligands. The anion in 2 can be described as a square of disubstituted [PW10O37]9- anions linked by Fe(III)-O-Fe(III) bridges. Magnetic measurements performed on 1 and 2 have shown the occurrence of antiferromagnetic interactions between the iron ions and have allowed the coupling constants between the magnetic centers to be determined.
authors.affiliation: Institut Lavoisier, UMR 8180, Université de Versailles Saint-Quentin-en Yvelines, 45 Avenue des Etats-Unis, 78035, Versailles Cedex, France.
authors.forename: Céline
authors.initials: C
authors.lastname: Pichon
authors.forename: Anne
authors.initials: A
authors.lastname: Dolbecq
authors.forename: Pierre
authors.initials: P
authors.lastname: Mialane
authors.forename: Jérôme
authors.initials: J
authors.lastname: Marrot
authors.forename: Eric
authors.initials: E
authors.lastname: Rivière
authors.forename: Francis
authors.initials: F
authors.lastname: Sécheresse