Synthesis and structural characterization of cationic octahedral oxorhenium(V) complexes with bidentate imidazole derivatives

Cationic distorted octahedral complexes [ReOCl(OEt)(L)(PPh₃)]X {L = 2-(1-ethylaminomethyl)-1-methylimidazole (eami), 2-(1-methylaminomethyl)-1-methylimidazole (mami), 2-(1-ethylthiomethyl)-1-methylimidazole (etmi); X=ReO₄, PF₆} were prepared by reaction of trans-[ReOCl₃(PPh₃)₂] with a twofold molar excess of L in ethanol under anaerobic conditions. X-ray structure determinations of [ReOCl(OEt)(eami)(PPh₃)](ReO₄) (1a) and its etmi equivalent (3a) were performed. In 1a coordination of the chloride occurs trans to the imidazole nitrogen. However, in 3a the chloride is coordinated trans to the ethereal sulfur donor of etmi.     

Synthesis,characterization and structure of oxorhenium(V) complexes with 2-methylmercaptobenzamide

The neutral, mononuclear complex [ReO(mta)₂Cl] (1) [Hmta?=?2-(methylmercapto)aniline] was prepared by reaction of trans-[ReOCl₃(PPh₃)₂] with a twofold molar excess of Hmta in methanol. The oxo-bridged dimer (μ-O)[ReO(mta)₂]₂ (2) was synthesized by reacting [ReOCl₃(PPh₃)₂] with a twofold excess of Hmta in a 9?:?1 acetone/water mixture. The compounds were characterized by spectroscopy and complex 1 also by X-ray crystallography. Complex 1 has a distorted octahedral geometry with the chloride coordinated trans to the oxo group, and with the chelating ligands in the equatorial plane in a cis-N cis-S configuration.     

Syntheses and crystal structures of neutral oxorhenium(V) complexes of N2O2-donor tripodal ligands

The neutral distorted octahedral complexes [ReOCl(L)] {H₂L = N,N-bis(2-hydroxybenzyl)-2-(2-aminoethyl)dimethylamine (H₂had); N,N-bis(2-hydroxybenzyl)-aminomethylpyridine (H₂hap); N,N-bis(2-hydroxybenzyl)-2-(2-aminoethyl)pyridine (H₂hae)} were prepared by the reaction of trans-[ReOCl₃(PPh₃)₂] with a twofold molar excess of H₂L in ethanol. X-ray structure determinations of [ReOCl(had)] (1) and [ReOCl(hap)] (2) were performed, and the structures compared. In both complexes the choride is coordinated trans to the tripodal tertiary amino nitrogen, with a phenolate oxygen trans to the oxo oxygen.     

Synthesis and characterization of nickel(II) maltolate complexes containing ancillary bisphosphine ligands

Cationic nickel(II) complexes containing chelating O,O′-donor maltolate or ethyl maltolate ligands in conjunction with bidentate bisphosphine ligands Ph₂P(CH₂) _n PPh₂ were prepared by a one-pot reaction starting from nickel(II) acetate, bisphosphine, maltol (or ethyl maltol), and trimethylamine, and isolated as their tetraphenylborate salts. An X-ray structure determination of [Ni(maltolate)(Ph₂PCH₂CH₂PPh₂)]BPh₄ shows that the maltolate ligand binds asymmetrically to the (slightly distorted) square-planar nickel(II) center. The simplicity of the synthetic method was extended to the synthesis of the known platinum(II) maltolate complex [Pt(maltolate)(PPh₃)₂]BPh₄ which was obtained in high purity.     

Trinuclear Schiff base complexes with uranium(V) and copper(II) or zinc(II) ions

Treatment of the uranium(IV) complexes [{ML¹(py)}₂U^IV] (M = Cu, Zn; L¹ = N,N′-bis(3-hydroxysalicylidene)-1,3-propanediamine) with silver nitrate in pyridine led to the formation of the corresponding cationic uranium(V) species which were found to be thermally unstable and were converted back into the parent U^IV complexes; no electron transfer was observed in solution between the U^IV and U^V compounds. In the crystals of [{ML¹(py)}₂U^IV][{ML¹(py)}₂U^V][NO₃], the neutral U^IV and cationic U^V species are clearly identified by the distinct U–O distances. Similar reaction of [{ZnL²(py)}₂U^IV] [L² = N,N′-bis(3-hydroxysalicylidene)-1,4-butanediamine] with AgNO₃ gave crystals of [{ZnL²(py)}U^V{ZnL²(py)₂}][NO₃] but the copper counterpart was not isolated. Crystals of [{ZnL¹(py)}₂U^V][OTf] · THF (OTf = OSO₂CF₃) were obtained fortuitously from the reaction of [Zn(H₂L¹)] and U(OTf)₃.     

Syntheses and structural transformations of oxorhenium(V) complexes with triazine and imidazole derivatives: mixed ligand complexes with thiocyanate, 8-hydroxyquinoline and 1,10-phenanthroline

Mononuclear oxorhenium(V) complexes [ReO(HL¹ or H₂L²)(PPh₃)(OH₂)Cl]Cl, {H₂L^{1 =} 1-(2-hydroxyphenyl)butane-1,3-dione-3-(5,6-diphenyl-1,2,4-triazine-3-ylhydrazone) and H₃L^{2 =} 1-(2-hydroxyphenyl)butane-1,3-dione-3-(1H-benzimidazol-2-ylhydrazone)}, have been synthesized by ligand exchange with trans-trichloromonooxo-bis(triphenylphosphine) rhenium(V). The reaction of a 1?:?1 mixture of either NH₄SCN, 1,10-phenanthroline (1,10-phen) or 8-hydroxyquinoline (8-OHquin) and H₂L¹ or H₃L², with trans-ReOCl₃(PPh₃)₂ yielded the mononuclear oxorhenium(V) complexes, [ReO(HL¹ or H₂L²)(PPh₃) (SCN)Cl], [ReO(HL¹)(1,10-phen)Cl]Cl, [ReO(H₂L²)(1,10-phen)(OH₂)]Cl₂·H₂O and [ReO(HL¹ or H₂L²) (8-Oquin)Cl]. Thermal studies on these complexes showed structural transformations from mononuclear into binuclear complexes. [Re₂O₃(HL¹ or H₂L²)₂(PPh₃)₂Cl₂], [Re₂O₂(μ-L¹ or L²)₂(SCN)₂] and [Re₂O₃ (H₂L²)₂(1,10-phen)₂]Cl₂, were synthesized pyrolytically in the solid state from the respective precursor rhenium complexes. The structures of all complexes and the corresponding thermal products were elucidated using elemental analyses, conductance, IR and electronic absorption spectra, magnetic moments and ¹H NMR and TG-DSC measurements. The prepared complexes and their thermal products have octahedral configurations. The ligands H₂L¹ or H₃L² behave as monoanionic bidentate or monoanionic tetradentate ligands towards the oxorhenium ions. The antifungal activities of the metal complexes towards Alternaria alternata and Aspergillus niger were tested and showed comparable behavior with well known antibiotics.     

Mixed-ligand complexes of copper VII. Polarographic studies on copper-carboxylate-aminocarboxylate complexes

The formation constants of mixed-ligand complexes with hetero donors of the type CuAB where A is a carboxylic acid such as lactic acid or oxalic acid and B is an α−or β-amino acid are studied by polarography. The mixed-ligand stabilisation constant clearly indicates the preferred formation of copper(II) mixedligand complexes with hetero donors over homo donors. The other driving forces leading to the favoured formation of mixed-ligand complexes are also discussed.     

Hydride and dihydrogen dicarbonylrhenium(I) complexes with phosphites, phosphonites and phosphinites

Photoirradiation of a toluene solution of [ReH(CO)₃(L)] [S. Bolaño, J. Bravo, R. Carballo, S. García-Fontán, U. Abram, E.M. Vázquez-López, Polyhedron 18 (1999) 1431-1436] [L = 1,2-bis(diphenylphosphinoxy)ethane] in the presence of PPh_n(OR)_3−n (n = 0, 1; R = Me, Et) leads to the replacement of a CO ligand by the corresponding monodentate phosphite or phosphonite ligand to give new hydride compounds of formula [ReH(CO)₂(L)(L′)] [L′ = P(OMe)₃ (1); P(OEt)₃ (2); PPh(OMe)₂ (3); PPh(OEt)₂ (4)]. Protonation of compounds 1-4 in CD₂Cl₂, with HBF₄.OMe₂ or with HOOCCF₃ at 193 K in a NMR tube, gave the corresponding dihydrogen complexes. When the temperature was increased from 193 to 293 K, the η²-H₂ ligand was replaced by OMe₂ or ⁻OOCCF₃ groups (depending on the acid employed) to give new stable complexes and the loss of H₂ gas.     

Trichloro-mono- β -diketonato oxorhenium(V) complexes: synthesis,characterization and crystal structure

Oxorhenium(V) complexes of β-diketonate systems have been synthesized and isolated in pure form. The red complexes n-Bu₄N[ReO(R₁COCHCOR₂)Cl₃] (acac, R₁=R₂=CH₃; bzac, R₁=CH₃ and R₂=C₆H₅; bzbz, R₁=R₂=C₆H₅) have been characterized by elemental analyses, spectroscopic and other physico-chemical tools. One complex, n-Bu₄N[ReO(bzbz)Cl₃] (1c) has been subjected to single-crystal X-ray analysis. In the structure of the anion, the metal has a six-coordinate octahedral environment in which the bidentate β-diketone ligand is cis and trans to the terminal oxygen.     

Different coordination modes of tetradentate Schiff bases in monomeric and dimeric oxorhenium(V) complexes

The reactions of the tetradentate amine-phenol type Schiff bases H₂sal₂en (1,2-ethylenebis(salicylideneimine) and H₂sal₂mp (1,2-benzylenebis(salicylideneimine)) with trans-[ReOCl₃(PPh₃)₂] or (n-Bu₄N)[ReOCl₄] in air gave the products (µ-O)[ReO(sal₂en)]₂ (1) and [ReOCl(sal₂mp)] (2), respectively. X-ray and spectroscopic studies have shown that 1 contains the linear O=Re–O–Re=O grouping, with the four donor atoms of sal₂en^2? coordinating in the square plane cis to the oxo ions. In 2, a cis oxo-chloro arrangement is observed with a phenolic oxygen being coordinated trans to the oxo group. The terminal Re=O bond lengths in 1 and 2 are 1.709(4) and 1.683(3)?Å, respectively.     

Rhenium(I) tricarbonyl complexes with bispyridine ligands attached to sulfur-rich core: Syntheses, structures and properties

Rhenium(I) tricarbonyl complexes with bispyridine ligands bearing sulfur-rich pendant, Re(CO)₃(Medpydt)X (Medpydt = dimethyl 2-(di(2-pyridyl)methylene)-1,3-dithiole-4,5-dicarboxylate; X = Cl, 1; X = Br, 2) and Re(CO)₃(MebpyTTF)X (MebpyTTF = 4,5-bis(methyloxycabonyl)-4′,5′-(4′-methyl-2,2′-dipyrid-4-ylethylenedithio)-tetrathiafulvalene; X = Cl, 5; X = Br, 6), were prepared from the reactions between Re(CO)₅X (X = Cl, Br) and Medpydt or MebpyTTF, respectively. Hydrolysis of the above complexes afforded the analogues with carboxylate derivatives, Re(CO)₃(H₂dpydt)X (X = Cl, 3; X = Br, 4) and Re(CO)₃(H₂bpyTTF)X (X = Cl, 7; X = Br, 8). The crystal structures for complexes 1 · 2H₂O, 5 and 6 were determined using X-ray single crystal diffraction. UV-Vis absorption spectra of the rhenium complexes show the intraligand and MLCT transitions. Electrochemical behaviors of all new compounds were studied with cyclic voltammetry. Upon irradiation, complexes 3-6 exhibit blue to red emissions in fluid solutions at the room temperature. The performance of complexes 3, 4, 7 and 8 as photosensitizers for anatase TiO₂ solar cells was preliminarily investigated as well.     

Coordination modes of histidine- or methioninehydroxamic acids in copper(II) mixed-ligand complexes with ethylenediamine in aqueous solution

The stability constants and coordination modes of the mixed-ligand complexes formed by copper(II) ion and ethylenediamine as a primary ligand and methioninehydroxamic acid (Metha) or histidinehydroxamic acid (Hisha) as a secondary ligand L were determined by potentiometric titration, UV–Vis and EPR spectroscopy. The obtained results suggest the formation of mixed-ligand species in basic solution with 4N coordination – both amine and hydroxamic nitrogens of Metha or Hisha (NH₂, N_ha) and two amine nitrogens of en (2 × NH₂) in the equatorial plane.     

Binary and ternary oxorhenium(V) complexes: synthesis,characterization, and crystal structure

A series of anionic five-coordinate binary oxorhenium(V) complexes with dithiolato ligands, Bu₄N[ReO(L¹)₂] (1a), Bu₄N[ReO(L²)₂] (1b), and Bu₄N[ReO(L³)₂] (1c), and a series of neutral octahedral ternary oxorhenium(V) complexes of mixed dithiolato and bipyridine ligands, [ReO(L¹)(bpy)Cl] (2a), [ReO(L²)(bpy)Cl] (2b), and [ReO(L³)(bpy)Cl] (2c) (where L¹H₂ = ethane-1,2-dithiol, L²H₂ = propane-1,3-dithiol, L³H₂ = toluene-3,4-dithiol, and bpy = 2,2′-bipyridine), were isolated and characterized by physicochemical and spectroscopic methods. The solid state structure of 1c was established by X-ray crystallography. All the mononuclear oxorhenium(V) complexes are diamagnetic. The redox behavior of all the complexes has been studied voltammetrically.     

Syntheses,characterizations and crystal structures of two new complexes, [Co2(CH2 =C(CH3)CO2)4(phen)2(H2O)2] and [Pb2(CH2 =C(CH3)CO2)4(phen)2]

Two new complexes, [Co₂(CH₂=C(CH₃)CO₂)₄(phen)₂(H₂O)₂] (1) and [Pb₂(CH₂=C(CH₃)CO₂)₄(phen)₂] (phen = 1,10-phenanthroline) (2), have been synthesized and structurally characterized by single crystal X-ray diffraction methods. There are two cocrystallized conformers of [Co(CH₂=C(CH₃)CO₂)₂(phen)(H₂O)] in the asymmetric unit of 1 with the Co atoms displaying similar coordination modes. In the asymmetric unit of 2, there exist two crystallographically independent [Pb(CH₂=C(CH₃)CO₂)₂(phen)] molecules with the Pb atoms showing completely different coordination geometries. Weak intermolecular interactions such as hydrogen bonding and π–π stacking are responsible for the supramolecular assembly and stabilization of the crystal structures of 1 and 2. The complexes are characterized by elemental analysis, IR spectra, and UV–Vis spectra. The fluorescent properties of 2 are also discussed.     

Heterobinuclear and Heterotrinuclear complexes of Oxorhenium(V) with Cu(II), Ni(II), Fe(III), UO2(VI) and Th(IV) in the solid state

New heteronuclear complexes containing oxorhenium(V), Cu(II), Ni(II), Fe(III), UO₂(VI) and Th(IV) ions were prepared by the reaction of the complex ligand, [ReO(H₄L)Cl]Cl₂, where H₄L = 8,17-dimethyl-6,15-dioxo-5,7,14,16-tetrahydrodibenzo[a,h][14]annulene-2,11-dicarboxylic acid, with the previous transition and actinide salts. Three heteronuclear Cu(II) complexes were isolated depending on the ratio of [ReO(H₄L)Cl]Cl₂?:?Cu(II) ion. When the ratios were 1?:?0.5, 1?:?1 and 1?:?2, the heteronuclear complexes {[ReO(H₃L)Cl]₂CuCl₂(OH₂)₂}SO₄ · H₂O (I), [ReO(H₃L)Cl₂Cu(OH₂)₂(SO₄)] (II) and {ReO(H₂L)Cl[Cu(OH₂)₃ SO₄]₂} (III) were obtained, respectively. Heteronuclear complexes of the other metal cations were obtained by mixing [ReO(H₄L)Cl]Cl₂ with the metal salt in the ratio 1?:?1 to obtain the heteronuclear complexes [ReO(H₃L)Cl₂Ni(OH₂)₂](NO₃)₂ (IV), [ReO(H₃L)Cl₃Fe(OH₂)₃](NO₃)₂ (V), [ReO(H₃L)ClUO₂(NO₃)₂ (OH₂)]Cl (VI) and [ReO(H₃L)Cl₃Th(NO₃)₂(OH₂)]NO₃ · 2H₂O (VII). The complex ligand coordinates with the heterometal ion via the carboxylate group, and the infrared bands ν_as COO and ν_s COO indicate that the carboxylate acts as a unidentate ligand to the heterometal cations. Cu(II) and Fe(III) cations in the heteronuclear complexes have octahedral geometry, while Ni(II) is square planar. Thermal studies explored the possibility of obtaining new heteronuclear complexes pyrolytically in the solid state from the corresponding mother complexes. The structures of the complexes were elucidated by conductance, IR and electronic spectra, magnetic moments, ¹H NMR and TG-DSC measurements as well as by mass spectroscopy.     

Coordination of 2,3-diaminopyridine in the diamidopyridinium mode to the ReO3+ core

2,3-Diaminopyridine (H₂dap) reacts with (n-Bu₄N)[ReOCl₄] to form an air-stable salt of composition [ReO(Hdap)₂]Cl·2H₂O. Spectroscopic studies and X-ray crystallography show that Hdap is coordinated in the monoanionic diamidopyridinium mode to the oxorhenium(V) center. The protonation of the pyridyl nitrogens and the charge on the complex have no influence on the bond lengths and angles, with the rhenium(V)–oxo and average Re–NH bond lengths equal to 1.688(4) and 1.993(5) Å, respectively.     

Geometrical characteristics of four-coordinate complexes of Ni,Pd, and Pt containing triphenylphosphine as ligand

A statistical analysis based on crystal structure results of 4-coordinated complexes of Ni, Pd, and Pt containing triphenylphosphine as ligand has been performed using the Cambridge Structural Data Base. Distorted square-planar coordination appears as the most probable one presented by these metals.

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Geometrische Charakteristika von vier-koordinierten Komplexen des Ni, Pd und Pt mit Triphenylphosphin als Ligand

Zusammenfassung Es wurde unter Verwendung der Cambridge Strukturdatenbank eine statistische Analyse von Resultaten an vier-koordinierten Komplexen des Ni, Pd und Pt mit Triphenylphosphin-Ligand durchgeführt. Dabei ergab sich eine verzerrte quadratisch-planare Koordination als die am meisten wahrscheinliche Geometrie.