Rhenium(IV) and rhenium(V) complexes with 3,5-dimethylpyrazole

Mono-and dinuclear Re^IV and Re^V complexes with 3,5-dimethylpyrazole (Me₂pzH) were synthesized. The cis-[Re₂O₃Cl₄(3,5-Me₂pzH)₄] complex (cis-1) was prepared by the reaction of NH₄ReO₄ with K[HB(Me₂pz)₃] in concentrated HCl or by refluxing of [ReCl₃(MeCN)(PPh₃)₂] with Me₂pzH in air. The bromide complex trans-[Re₂O₃Br₄(3,5-Me₂pzH)₄] (trans-2) was synthesized by passing dry HBr through a solution of [Re₂O₃Br₂(μ-3,5-Me₂pz)₂(3,5-Me₂pzH)₂] (4) in chloroform. The pyrazolate-bridged complex [Re₂O₃Cl₂(μ-3,5-Me₂pz)₂(3,5-Me₂pzH)₂] (3) was prepared from (Et₄N)₂[ReOCl₅] or Cs₂[ReOCl₅] and Me₂pzH. The corresponding bromide and iodide complexes [Re₂O₃X₂(3,5-Me₂pz)₂(3,5-Me₂pzH)₂] · C₆H₆ (X = Br (4) or I (5)) were synthesized by the reactions of (NH₄)₂[ReBr₆] or K₂[ReI₆], respectively, with Me₂pzH. The [ReO(OMe)(3,5-Me₂pzH)₄]Br₂ · · 3,5-Me₂pzH · 4H₂O complex (6) was obtained as a by-product in the synthesis of complex 4. The reaction of [ReNCl₂(PPh₃)₂] with Me₂pzH was accompanied by hydrolytic denitration giving rise to the mixed-ligand complex [Re₂O₃Cl₂(μ-3,5-Me₂pz)₂(3,5-Me₂pzH)(PPh₃)] (7). The reaction of (NH₄)₂[ReBr₆] with a Me₂pzH melt gave the trans-[ReBr₄(3,5-Me₂pzH)₂] · · Me₂CO complex (8). The structures of complexes 2 and 4–8 were established by X-ray diffraction. All compounds were characterized by elemental analysis, electronic absorption spectroscopy, ¹H NMR and IR spectroscopy, mass spectrometry, and cyclic voltammetry. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 52–59, January, 2006.     

The influence of solvent polarity on the tetrahedral-octahedral equilibrium of Co(II)complexes with 3,5-dimethylpyrazole

The configuration equilibrium:

(where DMPz = 3,5-dimethylpyrazole), has been studied spectrophotometrically in various non-aqueous polar solvents. The influence of solvent polarity on the K value has been investigated. Solvation studies have also been carried out on the tetrahedral species Co(SCN)₂(DMPz)₂, and the results are interpreted in terms of the polarity of the various solvents.     

Synthesis and structural characterization of new polynuclear complexes of 1-hydroxymethyl-3,5-dimethylpyrazole with Ni(II) and Fe(II)

The complexation of the simple 1-hydroxymethyl-3,5-dimethylpyrazole (HL) ligand with Fe and Ni salts leads to interesting polynuclear complexes in good yield. X-ray diffraction reveals that the resulting complexes (μ₄-L)₄Ni₄Cl₄(H₂O)₄ and (μ₂-L)₄(μ₃-L)₂Fe₈Cl₁₆(μ₄-O)₆ adopt cubane-type and open-cubane-type structures in the solid state.     

Copper(I) complex with BINAP and 3,5-dimethylpyrazole: synthesis and photoluminescent properties

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Nitric oxide binding and photodelivery based on ruthenium(II) complexes of 4-arylazo-3,5-dimethylpyrazole

Two fluorescent ligands, 3,5-dimethyl-4-(6'-sulfonylammonium-1'-azonaphthyl)pyrazole (dmpzn, 1) and 3,5-dimethyl-4-(4'-N,N'-dimethylaminoazophenyl)pyrazole (dmpza, 2) were obtained by condensation of ketoenolic derivatives with hydrazine. 1 and 2 formed the novel dinuclear complexes [(H(2)O)(3)ClRu(micro-L)(2)RuCl(H(2)O)(3)] (3 or 4) and [(H(2)O)(NO)Cl(2)Ru(micro-L)(2)RuCl(2)(NO)(H(2)O)] (6 or 7) (where L 1 = 2 or , respectively) which were characterized by IR, NMR and elemental analysis. The nitrosyl complexes were prepared by bubbling purified nitric oxide through methanol solutions of the corresponding ruthenium(II) chloroderivative or by reaction of the appropriate ligands with Ru(NO)Cl(3). Complexes 3 and 4 were found to bind NO, resulting in an increase in fluorescence. Ligand 1 also formed the mononuclear nitrosyl complex [Ru(NO)(bpy)(2)(dmpzn)]Cl(2) (8) which released NO in water at physiological pH and in the solid state as revealed by fluorescence and IR measurements, respectively.     

Magnetic properties of binuclear high-spin trimethylacetate nickel(II) complexes

The static magnetic susceptibility of mononuclear trimethylacetate nickel complex Ni(NH₂Ph)₄(OOCCMe₃)₂ (3) and binuclear complexes Ni₂(μ-OH₂)(μ-OOCCMe₃)₂(OOCCMe₃)₂(dipy)₂ (4) and Ni₂(μ-OOCCMe₃)₄py₂ (5) was measured in the temperature range of 2–300 K. The magnetic behavior of3 is typical of mononuclear complexes with the Ni¹¹ atom in the octahedral environment. Numerical calculations of the temperature dependence of magnetic susceptibility with inclusion of isotropic exchange interactions (J) and single-ion initial splitting parameters showed that the magnetic behavior of complexes4 and 5 can be interpreted in terms of ferromagnetic (for4) and antiferromagnetic (for5) interactions. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 437–442, March, 2000.     

Copper(II) complexes with aroylhydrazones

The coordination chemistry of copper(II) with tridentate aroylhydrazones is briefly discussed in this article. Two types of aroylhydrazones derived from aroylhydrazines and ortho-hydroxy aldehydes or 2-pyridine-carboxaldehyde have been used. The characterization of the complexes has been performed with the help of various physico-chemical techniques. Solid state structural patterns have been established by X-ray crystallography. In the solid state, structural varieties of these complexes are seen to range from monomeric, dimeric, polymeric and one-dimensional self-assembly via hydrogen bonds and π-π interactions. EPR spectroscopy and variable temperature magnetic susceptibility measurements have been used to reveal the nature of the coordination geometry and magnetic characteristics of these complexes.     

Cyanato-copper(II) complexes with organic ligands—XXIV. Diisocyanato-bis(3,5-dimethylpyrazole)copper(II)—the cyanate member of the coligand isomer

The title compound was prepared, and found to be isomeric with the known bis(1-carbamoyl-3,5-dimethylpyrazolato)copper(II). Its IR, far-IR, electronic     

Copper(II) complexes with N,N-dimethylbiguanide

The N,N-dimethylbiguanide (HDMBG) complexes [Cu₂(HDMBG)₂Cl₄] (1) and respectively [Cu(HDMBG)₂]Cl₂·2H₂O (2) exhibit in vitro antimicrobial activity. The complexes were characterised by IR, electronic as well as EPR spectra. The IR spectra of complexes show the pattern of N,N-dimethylbiguanide coordinated as chelate. The electronic and EPR data are in agreement with a square pyramidal stereochemistry for (1) and a square planar one for (2). The in vitro qualitative and quantitative antimicrobial activity assays showed that the complexes exhibited variable antimicrobial activity against Gram-negative strains (Escherichia coli, Klebsiella spp. and Enterobacter sp.) isolated from the hospital environment. The thermal analysis has evidenced the thermal intervals of stability and also the thermodynamic effects that accompany them. The thermal behaviour in nitrogen is complex according to TG and DTA curves including melting, dehydration as well as compounds decomposition.     

Oxidation of the iron(II) complex with 3,5-dimethylpyrazole by air in acetonitrile and dibenzyl ether

The reaction of the polymeric complex FeCl₂(NCMe)₂ (1) with 3,5-dimethylpyrazole (Hdmpz) yields the tetrahedral complex [Fe(Hdmpz)₃Cl]Cl (2), which is oxidized by air in acetonitrile to give [Fe(Hdmpz)₃Cl₂]₂(μ-O) (3). The reaction of FeCl₃ · 6H₂O with Hdmpz also leads to complex 3. The oxidation of complex 2 in a dichloromethane solution of dibenzyl ether gives the complex (Hdmpz)FeCl₂[η²-N,O-(dmpz)C(O)H(Ph)] (4), which contains a coordinated tetrahedral intermediate product of condensation of Hdmpz and benzaldehyde. The structures of complexes 1–4 are discussed on the basis of X-ray crystallographic data.     

Copper(II) and zinc(II) complexes with 2-formylpyridine-derived hydrazones

In the present work 2-formylpyridine-para-chloro-phenyl hydrazone (H2FopClPh) and 2-formylpyridine-para-nitro-phenyl hydrazone (H2FopNO₂Ph) were obtained, as well as their copper(II) and zinc(II) complexes [Cu(H2FopClPh)Cl₂] (1), [Cu(2FopNO₂Ph)Cl] (2), [Zn(H2FopClPh)Cl₂] (3) and [Zn(H2FopNO₂Ph)Cl₂] (4). Upon re-crystallization in DMSO:acetone conversion of 2 into [Cu(2FopNO₂Ph)Cl(DMSO)] (2a) and of 4 into [Zn(2FopNO₂Ph)Cl(DMSO)] (4a) occurred. The crystal structures of 1, 2a, 3 and 4a were determined.     

Copper(II) complexes with a flexible oxamato ligand

We report on a convenient synthesis of the ligand precursor, diethylethylene-1,2-bis(oxamate), (Et₂H₂oeo, 1), and show how a partial and preferential hydrolysis of the ester group can give rise to the dianionic ligand, (H₂oeo)²⁻. Reaction of this ligand with Cu(II) affords the neutral dimeric species, [Cu₂(H₂oeo)₂], which has a low aqueous solubility. We describe the crystal structure of the hydrate Cu₂(H₂oeo)₂(H₂O)₄ (2) and report magnetic studies that show a weak exchange interaction in the solid. Under more basic conditions and in the presence of Cu(II) ions, we are able to avoid amide cleavage and yet deprotonate the amide group, resulting in the formation of the highly soluble [Cu(Hoeo)₂]⁴⁻ complex anion. The structure of (NBu₄)₄[Cu(Hoeo)₂](H₂O)₄ (3) is described and compared with the recently reported anhydrous phase.     

Polynuclear rhodium(I) complexes with 3,3′,5,5′-tetramethyl-4,4′-bipyrazole and 4,4′-methylen-bis(3,5-dimethylpyrazole)

Summary The reaction of [RhClY₂]₂ (Y₂ = diolefin; Y = CO) with 3,3,5,5-tetramethyl-4,4-bipyrazole and 4,4-methylen-bis (3,5-dimethylpyrazole) (H₂LL) leads to binuclear complexes of the type (H₂LL) [RhClY₂]₂. The addition of triethylamine to the latter complexes gives polynuclear [(LL){RhY₂}₂]_n derivatives. Related compounds of formula [(LL){RhX(PPh₃)}₂]_n (X = CO or CS) are also reported.Part of this paper was presented at the VIIIth International Congress of Heterocyclic Chemistry which was held in Graz, Austria. August 1981.     

Copper(II) complexes of pyrrolidine dithiocarbamate

Copper(II)-pyrrolidine dithiocarbamate (PDTC) complexes having the general formula, [Cu(PDTC)₂], [Cu(PDTC)X₂]⁻ (where X = Cl⁻, I⁻, CN⁻, SCN⁻) and [Cu(PDTC)(en)]⁺ (en = ethylenediamine) have been prepared and characterized by IR spectroscopy and by thermogravimetric analysis (TGA and DTA). The IR data suggests that coordination of pyrrolidine dithiocarbamate (PDTC) takes place through the two sulphur atoms in a symmetrical bidentate fashion. The results of thermal analysis are consistent with the proposed composition of the complexes.