Chiral palladium complexes with monoterpenoids oximes

Oximes of cis-caran-4-one, 3α- and 3β-hydroxycaran-4-ones, cis-verbanone, menthone, and 2β-hydroxybornan-3-one have been synthesized. The obtained oximes react with lithium tetrachloropalladate to give new chiral palladium complexes containing mono-or bidentate oxime ligands.     

Channel architecture via self assembly of oxamide oximes complexes

The nickel(II) and palladium(II) complexes of oxamide oximes substituted with alkyl chains of different length (C4-C8) were synthesized from the reaction of dichloroglyoxime with the corresponding amine derivatives. All compounds have been characterized by X-ray diffraction on single crystals and were found to be centrosymmetric at the metal center which is bound by the four oximic nitrogen atoms of two ligands in a square planar environment. Crystal structure analyses of Ni(II) and Pd(II) complexes showed that all of the Pd(II) complexes but only the hexyl-substituted oxamide oxime Ni(II) complex form infinite tubular channels. Their conformational analyses were carried out in order to understand the role of the chain length and of the metal center in the formation of the tubular channels and it was found that the formation of infinite tubular channels in crystals of Ni(II) and Pd(II) alkyl-substituted oxamide oxime complexes is related to the orientation of the alkyl chains relative to the central core.     

Stereoselective synthesis of cobalt(III) anionic complexes with chiral pyruvylaminoacid oximes and metal–ligand interactions in aqueous solution

A series of cobalt(III) anionic complexes with hydroxyimino analogs of dipeptides – oximes of pyruvylglycine, pyruvyl-l-alanine, pyruvyl-l-methionine and pyruvyl-l-phenylalanine (H₂pamaco, amac = amino acid) of composition Cat₃[Co(H₋₁pamaco)₂] · nH₂O (Cat – a monovalent metal cation) has been synthesized and investigated by UV–Vis, CD and ¹H NMR spectroscopy. It was established that for the two latter ligands, non-racemic mixtures of two diastereomeric complexes were formed as a result of synthesis. In comparison with the complex containing pyruvyl-l-alanine, in which the relative content of R (C₂) and S (C₂) isomers is approximately equal, the presence of bulky substituents in the molecules of Met- and Phe-containing ligands results in a significant discrimination in formation of the S (C₂) isomer. This conclusion was drawn upon analysis of the CD and NMR spectral data as well as from molecular modeling. The relative content of the diastereomers was evaluated on the basis of NMR data. The protonation constants of the ligands have been determined in aqueous solution by glass electrode potentiometry, whereas their interactions with Co(II) were studied both under argon and oxygen atmosphere.     

Thiosulfate metal complexes

The electronic structure of the thiosulfate ions was determined, which made it possible to predict and confirm experimentally for the first time the nature of their ³³S NMR spectra containing two signals of functionally different sulfur atoms. The results of NMR study on different nuclei and the EPR data indicated that the thiosulfate ions as bifunctional ligands enter the coordination sphere of metals with different nature in accordance with the principle of hard and soft acids and bases. The general scheme of the redox transformations of the thiosulfate ions as a result of homo-and heterolytic cleavage of the S-S bonds or the charge transfer in a metal-ligand system was proposed.     

Zeolite encapsulated metal complexes

The various strategies for the preparation of zeolite ship-in-a-bottle complexes are reviewed. Key examples of the cluster, flexible ligand, template and zeolite synthesis methods are described. Evidence for the intrazeolite location of the metal complexes as well as the prevailing interpretation of these results have been organized in terms of the various methods of characterization. A brief summary of known reactivity studies of zeolite encapsulated metal complexes, including catalytic oxidations and hydrogenations, is also presented.     

Divalent transition metal complexes

4-(4-ethoxy-phenylhydrazono)-1-phenyl-3-methyl-1H-pyrazolin-5(4H)-one (5a) (H-EMPhP) as ligand and its Cu(II), Co(II) and Ni(II) complexes 4(a-c) were synthesized and characterized by their thermal and spectral properties. The azocoupling product (H-EMPhP), able of azo-hydrazone tautomerism 5(a-d), act as a bidentate ligand involving in coordination the azogroup nitrogen of its common anion (7) and the oxygen atom that is bound to the pyrazole ring of the mentioned anion (7).     

Colloidal metal dispersions and metal complexes in hydrocarbons

Stable dispersions of colloidal metals in hydrocarbons have been prepared by a novel phase-transfer method. The metals were gold, silver, palladium and ruthenium; the hydrocarbons were n-hexane, cyclohexane and benzene. The phase transfer of colloidal metal particles from an aqueous phase to a hydrocarbon phase was achieved by adding salt to the emulsion of hydrocarbon in the aqueous suspension of metal with sodium oleate. The salts were sodium chloride, magnesium chloride, sodium sulfate, etc. The size distributions of the metal particles in the resulting hydrocarbon suspensions were almost the same as that of the original aqueous suspension. The dispersions of colloidal metals in hydrocarbons were stable for a long period of time without the addition of hydrocarbon-soluble stabilizer. The critical phase-transfer concentrations of various salts were determined. The phase-transfer powers of cations were larger than those of anions. Those of divalent and trivalent cations were exceedingly larger than that of the monovalent cation. The concentration of colloidal metal dispersed in hydrocarbon was achieved by using the phase-transfer method.     

Bivalent transition metal complexes of o-hydroxyacetophenone [N-(3-hydroxy-2-naphthoyl)] hydrazone: spectroscopic, antibacterial, antifungal activity and thermogravimetric studies

Schiff base complexes of Cu(II), Ni(II) and Zn(II) with the o-hydroxyacetophenone [N-(3-hydroxy-2-naphthoyl)] hydrazone (H(2)o-HAHNH) containing N and O donor sites have been synthesized. Both ligand and its metal complexes were characterized by different physicochemical methods, elemental analysis, molar conductivity ((1)H NMR, (13)C NMR, IR, UV-visible, ESR, MS spectra) and also thermal analysis (TG and DTG) techniques. The discussion of the outcome data of the prepared complexes indicates that the ligand behave as a bidentate and/or tridentate ligand. The electronic spectra of the complexes as well as their magnetic moments suggest octahedral geometries for all isolated complexes. The room temperature solid state ESR spectrum of the Cu(II) complex shows d(x2-y2) as a ground state, suggesting tetragonally distorted octahedral geometry around Cu(II) centre. The molar conductance measurements proved that the complexes are non-electrolytes. The kinetic thermodynamic parameters such as: E(#), ΔH(#), ΔG(#), ΔS(#) are calculated from the DTG curves, for the [Ni(H(O)-HAHNH)(2)] and [Zn(H(2O)-HAHNH)(OAc)(2)]·H(2)O complexes using the Coats-Redfern equation. Also, the antimicrobial properties of all compounds were studied using a wide spectrum of bacterial and fungal strains. The [Cu(Ho-HAHNH)(OAc)(H(2)O)(2)] complex was the most active against all strains, including Aspergillus sp., Stemphylium sp. and Trichoderma sp. Fungi; E. coli and Clostridium sp. Bacteria.     

Triangular Ni(II) complexes from the use of 2-pyridyl oximes

The reactions of representative 2-pyridyl oximes with Ni^II salts in the presence of a base have been investigated. The synthetic study has led to the new triangular complexes [Νi₃(ppko)₆]·2H₂O·0.5EtOH·MeOH (1·2H₂O·0.5EtOH·MeOH), [Νi₃(mpko)₃(HCO₂)₂(mpkoH)₂](ClO₄) (2) and [Νi₃(ppko)₃(HCO₂)₂(ppkoH)₂](ClO₄) (3), where ppko⁻ is the anion of phenyl(2-pyridyl)ketone oxime and mpko⁻ is the anion of methyl(2-pyridyl)ketone oxime. The structures of compounds 1 and 2 have been determined by single crystal X-ray diffraction. The ppko⁻ ligand in 1 adopts four different coordination modes including the unique N_pyridylO_oximate chelating one which gives rise to a 6-membered chelating ring, while the neutral and the deprotonated oxime ligands in 2 adopt three different coordination modes. The magnetic properties of 1 and 2 have been studied by variable-temperature dc magnetic susceptibility techniques which indicate antiferromagnetic interactions.     

Bivalent and trivalent iron complexes of acyclic hexadentate ligands providing pyridyl/pyrazine-amide-thioether coordination

Acyclic pyridine-2-carboxamide- and thioether-containing hexadentate ligand 1,4-bis[o-(pyridine-2-carboxamidophenyl)]-1,4-dithiobutane (H(2)bpctb), in its deprotonated form, has afforded purple low-spin (S = 0) iron(II) complex [Fe(bpctb)] (1). A new ligand, the pyrazine derivative of H(2)bpctb, 1,4-bis[o-(pyrazine-2-carboxamidophenyl)]-1,4-dithiobutane (H(2)bpzctb), has been synthesized which has furnished the isolation of purple iron(II) complex [Fe(bpzctb)].CH(2)Cl(2) (4) (S = 0). Chemical oxidation of 1 by [(eta(5)-C(5)H(5))(2)Fe][PF(6)] or [Ce(NO(3))(6)][NH(4)](2) led to the isolation of low-spin (S = 1/2) green Fe(III) complexes [Fe(bpctb)][PF(6)] (2) or [Fe(bpctb)][NO(3)].H(2)O (3), and oxidation of 4 by [Ce(NO(3))(6)][NH(4)](2) afforded [Fe(bpzctb)][NO(3)].H(2)O (5) (S = 1/2). X-ray crystal structures of 1 and 4 revealed that (i) in each case the ligand coordinates in a hexadentate mode and (ii) bpzctb(2-) binds more strongly than bpctb(2-), affording distorted octahedral M(II)N(2)(pyridine/pyrazine)N'(2)(amide)S(2)(thioether) coordination. To the best of our knowledge, 1 and 4 are the first examples of six-coordinate low-spin Fe(II) complexes of deprotonated pyridine/pyrazine amide ligands having appended thioether functionality. The Fe(III) complexes display rhombic EPR spectra. Each complex exhibits in CH(2)Cl(2)/MeCN a reversible to quasireversible cyclic voltammetric response, corresponding to the Fe(III)-Fe(II) redox process. The E(1/2) value of 4 is more anodic by approximately 0.2 V than that of 1, attesting that compared to pyridine, pyrazine is a better stabilizer of iron(II). Moreover, the E(1/2) value of 1 is significantly higher (approximately 1.5 V) than that reported for six-coordinate Fe(II)/Fe(III) complexes of the tridentate pyridine-2-carboxamide ligand incorporating thiolate donor site.     

Titanium alkali metal nitrido complexes

Treatment of [(Ti(eta5-C5Me5)(mu-NH))3(mu3-N)] with alkali metal bis(trimethylsilyl)amido reagents in toluene afforded the complexes [M(mu3-N)(mu3-NH)2[Ti3(mu5-C5Me5)3(mu3-N)]]2 (M = Li (2), Na, (3), K (4)). The molecular structures of 2 and 3 have been determined by X-ray crystallographic studies and show two azaheterometallocubane cores [MTi3N4] linked by metal-nitrogen bonds. Reaction of the lithium derivative 2 with chlorotrimethylsilane or trimethyltin chloride in toluene gave the incomplete cube nitrido complexes [Ti3(eta5-C5Me5)3(mu-NH)2(mu-NMMe3)(mu3-N)] (M = Si (5), Sn (6)). A similar reaction with indium(I) or thallium(I) chlorides yielded cube-type derivatives [M(mu3-N)(mu3-NH)2[Ti(eta5-C5Me5)3(mu3-N)] (M=In (7), Tl (8)).     

Tribologically active azomethine metal complexes

Russian Journal of General Chemistry - Oil-soluble bis(salicylideneiminates) were prepared chemically (from acetates of 3d-metals) and electrochemically (by anodic dissolution of complex forming...