Hexa-μ-acetato-chlorido-(μ-N,2-dioxodo-benzene-1-carboximidato)-μ3-oxido-tetra-iron(III)-water (1/1) and hexa-μ-acetato-(μ-N,2-dioxodo-benzene-1-carboximidato)fluorido-μ3-oxido-tri-pyridine-tetra-iron(III)-pyridine-water (1/1/0.24).

Cassandra L Ward,Matthew J Allen,Jacob C Lutter

doi:10.1107/s2056989021009208

Abstract

The title compounds, [Fe4(C2H3O2)6(C7H4O3)FO(C5H5N)3]·C5H5N·0.24H2O (1-F) and [Fe4(C2H3O2)6(C7H4O3)ClO(C5H5N)3]·H2O (1-Cl) were synthesized using a self-assembly reaction in methanol and pyridine with stoichiometric addition of salicyl-hydroxamic acid (H3shi), acetic acid (HOAc), and the appropriate ferric halide salt. The compounds crystallize as solvates, where 1-F has one pyridine mol-ecule that is disordered about a twofold axis and one water mol-ecule with an occupancy of 0.24 (2); and 1-Cl has one water mol-ecule that is disordered over two sites with occupancies of 0.71 (1) and 0.29 (1). The space groups for each analog differ as 1-F crystallizes in Fdd2 while 1-Cl crystallizes in P21. The difference in packing is due to changes in the inter-molecular inter-actions involving the different halides. The two mol-ecules are mostly isostructural, differing only by the torsion of the pyrine ligands and slight orientation changes in the acetate ligands. All of the iron(III) ions are in six-coordinate octa-hedral ligand field geometries but each one exhibits a unique coordination environment with various numbers of O (four to six) and N (nought to two) atom donors. Bond-valence sums confirm each iron is trivalent. The hydroximate ligand is bound to three iron(III) ions using a fused chelate motif similar to those in metallacrown compounds.

Highlights

Examples of hydroximate binding as fused chelate rings has been dominated by a class of coordination compounds known as metallacrowns
We describe two tetra-iron(III) compounds that have a fused chelate motif similar to metallacrowns but that are not examples of metallamacrocycles (Figs. 1 and 2). This fused chelate motif is complemented by six acetate ligands, a 3-oxo ligand, and three pyridine ligands to complete the octahedral ligand fields of the four iron ions
Fe1 is bound to the 2-oxime oxygen and carbonyl oxygen of shi3– to form a pentagonal chelate ring, an oxygen from an acetate ligand, the nitrogen from two pyridine ligands, and the respective halide for each compound

Summary

Chemical context

Examples of hydroximate binding as fused chelate rings has been dominated by a class of coordination compounds known as metallacrowns. We describe two tetra-iron(III) compounds that have a fused chelate motif similar to metallacrowns but that are not examples of metallamacrocycles Instead, this fused chelate motif is complemented by six acetate ligands, a 3-oxo ligand, and three pyridine ligands to complete the octahedral ligand fields of the four iron ions. This fused chelate motif is complemented by six acetate ligands, a 3-oxo ligand, and three pyridine ligands to complete the octahedral ligand fields of the four iron ions These compounds were a serendipitous discovery from metallacrown synthesis that can be formed with their own rational self-assembly reaction. Is bound to the 3-oxo, the 2-oxime oxygen of shi3–, and an oxygen from four acetate ligands For both compounds, the Fe—O(oxo) bonds are shorter than the

Structural commentary

Supramolecular features

Database survey

Synthesis and crystallization

Refinement