ic9802404_si_001.cif (44.13 kB)
Download fileNovel Square Arrangements in Tetranuclear and Octanuclear Iron(III) Complexes with Asymmetric Iron Environments Created by the Unsymmetric Bridging Ligand N,N,N‘-Tris((N-methyl)-2-benzimidazolylmethyl)-N‘-methyl-1,3-diamino-2-propanol
dataset
posted on 28.12.1998, 00:00 authored by Joe H. Satcher,, Marilyn M. Olmstead, Michael W. Droege, Sean R. Parkin, Bruce C. Noll, Leopold May, Alan L. BalchThe synthesis and characterization of novel tetranuclear and octanuclear iron(III) complexes with structures based
on a nearly square arrangement of four iron ions are reported. Reaction of ferric nitrate, sodium acetate, and the
unsymmetrical binucleating ligand HBMDP, where HBMDP is N,N,N‘-tris((N-methyl)-2-benzimidazolylmethyl)-N‘-methyl-1,3-diamino-2-propanol, in acetone/water yields the tetranuclear iron complex [Fe4(μ-O)2(μ-BMDP)2(μ-OAc)2]4+, which exhibits coordination number asymmetry. The structure of [Fe4(μ-O)2(μ-BMDP)2(μ-OAc)2](NO3)3(OH)·12H2O has been determined by single-crystal X-ray diffraction. Each (μ-BMDP) ligand spans
two iron(III) ions and causes these ions to become structurally distinct. Within this binuclear unit one iron atom
is five-coordinate with distorted square pyramidal geometry and an N2O3 donor set, while the other iron is six-coordinate with distorted octahedral geometry and an N3O3 donor set. Two of these binuclear units are linked
through a pair of oxo and acetato bridges to form the centrosymmetric tetranuclear complex. The coordinatively
nonequivalent iron atoms exhibit distinct Mössbauer spectroscopic parameters and produce a pair of doublets at
80 K. The iron(III) centers are coupled antiferromagnetically with a room-temperature moment of 1.9 μB per iron
with J = −103.3 cm-1, zJ‘ = −105.9 cm-1. The properties of the unsymmetric cation [Fe4(μ-O)2(μ-BMDP)2(μ-OAc)2]4+ are similar to those observed for binuclear iron proteins with comparable coordinative inequivalence.
Efforts to increase the solubility of [Fe4(μ-O)2(μ-BMDP)2(μ-OAc)2]4+ by metathesis with sodium tetrafluoroborate
resulted in the isolation of crystals of a new octanuclear iron species, [Fe8(μ-O)4(μ-BMDP)4(OH)4(μ-OAc)4](BF4)3(OH)·2CH3CN·8H2O(2), which has also been characterized by single-crystal X-ray diffraction. The
asymmetric unit consists of an Fe2(μ-O)(μ-BMDP)(μ-OAc)(OH) group which is externally bridged via the oxo
ions to form a molecular square with four of the eight iron ions at the corners. Both iron sites are six-coordinate
with distorted octahedral geometry. One has an N2O4 donor set; the other has an N3O3 donor set.
History
Usage metrics
Read the peer-reviewed publication
Categories
Keywords
BFN 2 O 3 donoriron atoms exhibitOAcunsymmetrical binucleating ligand HBMDPUnsymmetric Bridging Ligand NN 3 O 3 donorOHAsymmetric Iron Environments1.9 μ BM össbauer spectroscopic parametersiron ionsoctanuclear iron speciesFeNovel Square ArrangementsCNoctahedral geometryN 2 O 4 donorexhibits coordination number asymmetry