Eduard N. Chygorin

Heterometallic CoIII4FeIII2 Schiff Base Complex: Structure, Electron Paramagnetic Resonance, and Alkane Oxidation Catalytic Activity

The heterometallic complex [Co(4)Fe(2)OSae(8)]·4DMF·H(2)O (1) was synthesized by one-pot reaction of cobalt powder with iron chloride in a dimethylformamide solution of salicylidene-2-ethanolamine (H(2)Sae) and characterized by single crystal X-ray diffraction analysis, magnetic measurements, high frequency electron paramagnetic resonance (HF-EPR), and Mössbauer spectroscopies. The exchange coupling in the Fe(III)-Fe(III) pair is of antiferromagnetic behavior with J/hc = -190 cm(-1). The HF-EPR spectra reveal an unusual pattern with a hardly detectable triplet signal of the Fe(III) dimer. The magnitude of D (ca. 13.9 cm(-1)) was found to be much larger than in related dimers. The catalytic investigations disclosed an outstanding activity of 1 toward oxidation of cycloalkanes with hydrogen peroxide, under mild conditions. The most efficient system showed a turnover number (TON) of 3.57 × 10(3) with the concomitant overall yield of 26% for cyclohexane, and 2.28 × 10(3)/46%, respectively, for cyclooctane. A remarkable turnover frequency (TOF) of 1.12 × 10(4) h(-1) (the highest initial rate W(0) = 3.5 × 10(-4) M s(-1)) was achieved in oxidation of cyclohexane. Kinetic experiments and selectivity parameters led to the conclusion that hydroxyl radicals are active (attacking C-H bonds) species. Kinetic and electrospray ionization mass spectrometry (ESI-MS) data allowed us to assume that the trinuclear heterometallic particle [Co(2)Fe(Sae)(4)](+), originated from 1 in solution, could be responsible for efficient generation of hydroxyl radicals from hydrogen peroxide.

Tris(2,2′-bipyridine-κ2N,N′)cobalt(III) tris­(oxalato-κ2O1,O2)ferrate(III) mono­hydrate

The title compound, [Co(C10H8N2)3][Fe(C2O4)3]·H2O, consists of two discrete tris(chelate) metal ions (CoIIIN6 and FeIIIO6 chromophores) and a water molecule. The structure is highly symmetrical; the CoIII and FeIII ions occupy positions with site symmetry 3.2. The coordination polyhedra of the metal atoms have a nearly octahedral geometry with noticeable trigonal distortions. The Co—N and Fe—O bond lengths are equal by symmetry, viz. 1.981 (2) and 1.998 (4) Å, respectively. The cations and anions are arranged alternately along their threefold rotation axes parallel to [001], forming chains that are packed in a hexagonal manner. The water molecules occupy voids between the chains. The crystal under investigation was an inversion twin.

Bis(μ-4-nitro-2-{[2-(oxidometh-yl)phen-yl]imino-meth-yl}phenolato)bis-[chlorido(dimethyl sulfoxide)-iron(III)] dimethyl sulfoxide disolvate.

In the centrosymmetric dimeric title complex, [Fe2(C14H10N2O4)2Cl2(C2H6OS)2]·2C2H6OS, two {Fe(L)Cl(DMSO)} units (L is the tridentate ligand 4-nitro-2-{[2-(oxidomethyl)phenyl]iminomethyl}phenolate; DMSO is dimethyl sulfoxide) are bridged by two O atoms, with an Fe⋯Fe separation of 3.1838 (8) Å. The coordination polyhedron of the FeIII atoms can be described as distorted octahedral, with four Fe—O, one Fe—N and one Fe—Cl coordination bonds. The L ligand is not planar, the dihedral angle between the 2-(oxidomethyl)phenyl]imino and 4-nitro-2-(iminomethyl)phenolate planes being 48.54 (9)°. The solvent DMSO molecule is disordered over two orientations with equal occupancy.

Hexa­kis­(dimethyl­formamide-κO)manganese(II) μ-oxido-bis­[trichlorido­ferrate(III)]

The title compound, [Mn(C3H7NO)6][Fe2Cl6O], was obtained unintentionally as a product of an attempted synthesis of heterometallic complexes with Schiff base ligands using manganese powder and FeCl3·6H2O as starting materials. In the [Fe2OCl6]2− anion, the O atom and the Fe atom occupy positions with site symmetry and 3, respectively, resulting in a linear Fe—O—Fe angle and a staggered conformation. The octahedrally surrounded cation (site symmetry ) and the [Fe2Cl6O]2− anion are alternately stacked along [001].

Crystal structure of bis­(bis­{μ3-3-methyl-3-[(4-nitro-2-oxido­benzyl­idene)amino]­propane-1,3-diolato}tris­[chlorido­(dimethyl sulfoxide)­iron(III)]) dimethyl sulfoxide hepta­solvate dihydrate

The title compound is based on a trinuclear {Fe3(μ-O)4} core with an angular arrangement of the FeIII ions that can be explained by geometrical restrictions of two bulky ligands each coordinated to all the metal centres.

Triethyl-ammonium bis-{2-[(2-oxido-5-nitro-benzylidene)amino]-benzoato}ferrate(III) monohydrate.

In the title compound, [NH(C2H5)3][Fe(C14H8N2O5)2]·H2O, the iron(III) ion is hexacoordinated by four O atoms in the basal plane [Fe—O distances in the range 1.904 (4)–1.909 (4) Å] and two N atoms in the axial plane [Fe—N = 1.981 (4) and 1.985 (4) Å] of two tridentate fully deprotonated 2-{[(2-oxido-5-nitrophenyl)methylene]amino}benzoato (H2 L) ligands, forming a tetragonally elongated octahedral geometry. The triethylammonium cations and complex anions are linked by N—H⋯O hydrogen bonds into chains parallel to [100]. Disordered water molecules (occupancy ratio 0.6:0.4) occupy the voids in the crystal structure.

Tetra-kis(μ3-2-{[1,1-bis-(hy-droxy-meth-yl)-2-oxidoeth-yl]imino-meth-yl}-6-nitro-pheno-lato)tetra-copper(II).

The title cluster, [Cu4(C11H12N2O6)4], was obtained from the Cu0–FeCl2·4H2O–H4 L–Et3N–DMF reaction system (in air), where H4 L is 2-hydroxymethyl-2{[(2-hydroxy-3-nitrophenyl)methylidene]amino}propane-1,3-diol and DMF is dimethylformamide. The asymmetric unit consists of one Cu2+ ion and one dianionic ligand; a -4 symmetry element generates the cluster, which contains a {Cu4O4} cubane-like core. The metal ion has an elongated square-based pyramidal CuNO4 coordination geometry with the N atom in a basal site. An intramolecular O—H⋯O hydrogen bond is observed. The solvent molecules were found to be highly disordered and their contribution to the scattering was removed with the SQUEEZE procedure in PLATON [Spek (2009 ▶). Acta Cryst. D65, 148–155], which indicated a solvent cavity of volume 3131 Å3 containing approximately 749 electrons. These solvent molecules are not considered in the given chemical formula.