Asymmetric Heterodinuclear Fe^IIIM^II (M = Zn, Cu, Ni, Fe, Mn), Co^IIIFe^II and Fe^IICo^III Species: Synthesis, Structure, Redox Behavior, and Magnetism

Abstract

Reactions of an LFeIII unit with an M(PyA)3n− ion prepared in situ, where L represents 1,4,7‐trimethyl‐1,4,7‐triazacyclononane and PyA− is the monoanion of pyridin‐2‐aldoxime, yield heterodinuclear cations of the general formula [LFeIII(PyA)3M]2+, where M = ZnII (1), CuII (2), NiII (3), low‐spin FeII (4) and MnII (5). Additionally, we also prepared the diamagnetic species [LCoIII(PyA)3FeII]2+ (6). The FeIIICoII species could not be isolated because a facile intramolecular electron transfer leads to complex 7, [LFeII(PyA)3CoIII]2+. Compounds 1−7 contain three oximato anions as bridging ligands and are isostructural in the sense that they all contain a terminal metal(III) ion in a distorted octahedral environment (e.g., FeN3O3) and a second six‐coordinate metal ion M in a mostly trigonal‐prismatic MN6 geometry. Complexes 1−7 were characterized on the basis of elemental analyses, mass spectrometry, IR, UV/Vis, Mössbauer, and EPR spectroscopy, and variable‐temperature (2−295 K) magnetic susceptibility measurements. The solid‐state structures of 1−7 have also been determined by X‐ray crystallography. The cyclic voltammograms of the complexes reveal both ligand‐centered and metal‐centered redox processes. Analysis of the susceptibility data indicates the presence of antiferromagnetic exchange interactions that decrease in the following order: FeIIICuII (2) > FeIIINiII (3) > FeIIIMnII (5), as is expected. We have used X‐band EPR spectroscopy of 3 (FeIIINiII) at 2−6 K to establish the electronic ground state in great detail and to complement the magnetic susceptibility measurements. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Jahn–Teller distortions of six-coordinate CuII compounds: cis or trans?

“…Remarkably, there are compounds with two crystallographically independent molecules presenting cis and trans distortions, respectively. 18,34 Although these data should be taken with care, given the possibility of a dynamic Jahn-Teller effect or static disorder, 6,9,35 they are consistent with our computational results and seem to provide a good starting point for more accurate crystallographic studies.…”

Deliberate Synthesis for Magnetostructural Study of Linear Tetranuclear Complexes BIIIMnIIMnIIBIII, MnIIIMnIIMnIIMnIII, MnIVMnIIMnIIMnIV, FeIIIMnIIMnIIFeIII, and CrIIIMnIIMnIICrIII. Influence of Terminal Ions on the Exchange Coupling

“…Since the relevant bands in the IR spectra of comparable oxime-containing homo- and heterometal complexes have been described earlier , and the spectra of complexes 1 − 5 are also very similar, we refrain from discussing them in detail. The bands are given in the Experimental Section.…”

Use of the 2‐Pyridinealdoxime/N,N′‐Donor Ligand Combination in Cobalt(III) Chemistry: Synthesis and Characterization of Two Cationic Mononuclear Cobalt(III) Complexes

“…Complexes 1 and 2 join a small family of structurally characterized homo- [17, 18, 21] and heterometallic [22, 23] Co complexes featuring pao − as ligand. Many years ago Blackmore and Magee [24, 25] and Grant and Magee [26] studied the reactions between 2-pyridinealdoxime and various Co II sources under a variety of reaction conditions.…”