Synthesis and structural characterization of three dinuclear Copper(II) complexes incorporating pyrazolyl-derived ligands

Three new binuclear copper complexes of formulae $ \left[ {{\text{Cu}}_{2}^{\text{II}} {\text{Pz}}_{2}^{\text{Me3}} {\text{Br}}_{ 2} \left( {{\text{PPh}}_{ 3} } \right)_{ 2} } \right] $ (1), $ \left[ {{\text{Cu}}_{ 2}^{\text{II}} {\text{Pz}}_{2}^{\text{Ph2Me}} {\text{Cl}}_{ 2} \left( {{\text{PPh}}_{ 3} } \right)_{ 2} } \right] $ (2) and $ \left[ {{\text{Cu}}_{2}^{\text{II}} \left( {{\text{Pz}}^{\text{PhMe}} } \right)_{ 4} {\text{Cl}}_{ 4} } \right] $ (3) (Pz^Me3?=?3,4,5-trimethylpyrazole, Pz^Ph2Me?=?4-methyl-3,5-diphenylpyrazole and Pz^PhMe?=?3-methyl-5-phenylpyrazole) have been synthesized and characterized by chemical analysis, FTIR and ³¹P NMR spectroscopy and single-crystal X-ray diffraction. Complex 1 is a doubly bromo-bridged dimer, while complexes 2 and 3 are chloro-bridged dimers. The Cu(II) centers are in a distorted tetrahedral geometry for 1 and 2 and a distorted square pyramidal N₂Cl₃ environment for 3.     

Synthesis and characterization of triorganoantimony(V) complexes with bidentate ligands

Monochelated organoantimony(V) complexes of the type R₃Sb(OMe)L, where R = Me or Ph, and L is the anion of acetylacetone, 8-hydroxyquinoline, salicylaldehyde, o-hydroxyacetophenone or 2-hydroxy-1-naphthaldehyde have been obtained from triorganoantimony(V) dibromide and the sodium derivative of the ligands in a benzene-methanol mixture. Molecular weight determination in benzene reveals the monomeric nature of these complexes. IR and NMR data suggest that L acts as a bidentate ligand giving an octahedral environment for the antimony atom.     

Synthesis and characterization of cobalt(III) tetraaza macrocyclic complexes containing chloro and azido ligands

The complexes [Co(L)Cl₂]Cl · 4H₂O (1) and [Co(L)(N₃)₂]N₃ · 2H₂O (2) (L = 3,14-dimethyl-2,6,13,17-tetraazatricyclo [14,4,0^1.18,0^7.12]docosane) have been synthesized, and structurally characterized by X-ray crystallography, spectroscopy and cyclic voltammetry. The crystal structure of (1) is centrosymmetric and the cobalt(III) atom has an axially elongated octahedral geometry with four nitrogen atoms of the macrocycle and two chloride ligands. The cobalt(III) ion in (2) is coordinated to four nitrogen atoms from the macrocycle, and two azide ligands in an octahedral environment, which forms the 1D polymer through hydrogen bonding contacts involving the cation, azide anion and solvent water molecules. Electronic spectra of the complexes also exhibit a low-spin octahedral environment. Cyclic voltammetry of the complexes undergoes a one-electron wave corresponding to Co(III)/Co(II) processes. The electronic spectra and electrochemical behaviors of the complexes are significantly affected by the nature of the axial ligands.     

Synthesis and characterization of dinuclear vanadium(V) oxido peroxido tartrato complexes

Vanadium(V) oxido peroxido tartrato complexes have been prepared from aqueous-ethanolic media and characterized by spectroscopic methods. Using racemic tartaric acid for the synthesis, the simultaneous crystallization of racemic compounds (racemic phases) and racemic conglomerates (chiral phases) has been observed. The X-ray crystal structure of (NH₄)₄[V₂O₂(O₂)₂((2R,3R)–H₂tart)₂(μ–H₂O)][V₂O₂(O₂)₂((2S,3S)–H₂tart)₂(μ–H₂O)]·8H₂O (tart = C₄H₂O₆ ⁴⁻) revealed that the dinuclear anion is composed of two pentagonal bipyramidal polyhedra about vanadium atoms, which are joined to each other by sharing two oxygen atoms of hydroxyl groups and an oxygen atom from a bridging water ligand. The prepared compounds are not stable in aqueous solution; ⁵¹V NMR spectra exhibit the signals of several peroxido and non-peroxido vanadium(V) complexes.     

Synthesis and structural characterization of novel zinc(II) and cadmium(II) complexes with pyridine-phosphine chalcogenide ligands

New pyridine-phosphine chalcogenide ligands, tris[2-(2-pyridyl)ethyl]phosphine sulfide 1a and tris[2-(2-pyridyl)ethyl]phosphine selenide 1b, react with zinc(II) and cadmium(II) chlorides in EtOH at room temperature to afford complexes of compositions 2ZnCl₂·2L (2, L = 1a) and 3CdCl₂·2L (3a,b, L = 1a,b) in high yields. The solid-state structure of complexes 2, 3 has been proved by X-ray analysis data. Complex 2 is a centrosymmetric dimer, where two atoms of zinc are bonded by two bridging pyridine-phosphine sulfide ligands through N atoms. Complexes 3a,b exist as polymeric chains with each bridging ligand acting as a chelate N,S- or N,Se-donor to one cadmium(II) center and as a pyridine N-donor to the next cadmium(II) center.     

Mono and dinuclear Re(V) complexes with a hydrospirophosphorane HP∼O derived ligand: Synthesis,structural analysis and molecular dynamics

Two neutral mono and dinuclear rhenium(V) complexes, cis-ReOCl₂(P∼O)(pym) (1) and cis-[ReOCl₂(P∼O)]₂(μ–pym) (2 · (CH₃)₂CO), with the hydrospirophosphorane ligand HP∼O (HP∼O = octamethyl-2,2,3,3,7,7,8,8-tetraoxa-5λ⁵ 1,4,6,9-phosphaspiro-4,4-nonane) have been prepared. The coordination geometry of the complexes has been determined in solution by NMR and UV–Vis spectroscopy, as well as in the solid state by IR, FIR spectroscopy and single crystal X-ray diffraction. The complexes display distorted octahedral geometries. X-ray structures of 1 and 2 reveal that the ReCl₂NP fragments are equatorially disposed and the oxygens, terminal oxo and alcoholato, lie in axial positions. The pyrimidine coordinates as a monodentate or bridging ligand. Detailed temperature dependent ¹H NMR analysis for both 1 and 2 shows that in solution the diaza moiety exhibits hindered rotation about the Re–N bond. Furthermore two concomitant conformation changes, one in the metallacycle and the second in the phosphorus cycle, are also observed for dimer 2.     

Synthesis and structural characterization of cationic rhenium(V) and technetium(V) dioxo complexes containing four N-heterocyclic carbene ligands

Cationic dioxorhenium and dioxotechnetium complexes of the composition [MO(2)(L(1))(4)](+) (L(1) = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) have been prepared from various starting materials and studied spectroscopically and by X-ray crystallography. The metal-carbon distances range from 2.216(4) to 2.232(4) A indicating mainly sigma-bonding.     

Synthesis and characterisation of mono- and dinuclear diethyldithiocarbamatonickel(II) organochalcogenide complexes

The reaction of Ni(dtc)(PR₃)Cl (dtc=diethyldithiocarbamate, R=Ph or Bu) with HSC₆H₄Cl-4 or HSCH₂C₆H₄Cl-4 and Et₃N gave two types of complex. For PPh₃, the products were [Ni(dtc)(μ-SC₆H₄Cl-4)]₂ (1) and [Ni(dtc)(μ-SCH₂C₆H₄Cl-4)]₂ (2); whilst PBu₃ gave Ni(dtc)(PBu₃)(SC₆H₄Cl-4) (3). The structure of freshly prepared 3 was determined to be monomeric, as indicated by X-ray diffraction studies. However, at room temperature in solution, 3 was observed to slowly convert to 1. Structural identification of 1 and 2 and similar dimers, and structural identification of 3 and analogous monomers, were investigated by mass spectrometry. Electron impact mass spectrometry (EIMS) failed to confirm the proposed structures due to extensive decomposition in the mass spectrometer. In the electron impact (EI) mode, all complexes invariably decomposed to Ni(dtc)₂; on the other hand, fast atom bombardment (FAB) ionisation gave the expected molecular ions for all compounds.     

Synthesis and structural characterization of nickel(II) hexaazamacrotetracyclic complexes with phthalate ligands

Highly crosslinked polymeric networks formed by cyclodextrins (CD) have recently been shown to be highly versatile nanosponge systems, being for instance very efficient both for drug delivery and for pollutants removal. Here we report some molecular simulation results for dry and hydrated CD nanosponge models aimed to study their swelling behavior. We also report simulation results about the water mobility in these systems in terms of the calculated diffusion coefficient of “free” and of “bound” water molecules confined within the nanosponge cavities. Furthermore, we also suggest the presence of surface-constrained water molecules temporarily bound to the network surface but eventually set free in the bulk.     

Synthesis and characterization of dinuclear (Hedta)Ru(III) complexes with N-heterocyclic ligands: magnetic properties and DNA-binding studies

Two ruthenium(III) complexes containing ethylenediaminetetraacetate(edta), viz. [{Ru(Hedta)}₂L]·xH₂O L = 4,4′-bipyridine(bpy) (1) and 4,4′-azopyridine(Azpy) (2), have been synthesized by the reaction between K[Ru(Hedta)Cl]·1.5H₂O and the corresponding N-heterocycles. Complex 1 was determined by single-crystal X-ray diffraction. The products were characterized by IR, UV–vis, cyclic voltammetry, and magnetic techniques. Their DNA-binding activities were investigated using electronic absorption spectroscopic methods and ?uorescence quenching; the experimental results show that these two ruthenium complexes may bind to CT-DNA through intercalation modes.     

Synthesis and characterization of mono- and dinuclear copper(I) complexes with 3-(2-pyrimidinyl)-1,2,4-triazine

The mono- and dinuclear Cu(I) complexes [CuI(PPh₃)(pmtz)] (1) and [{Cu(PPh₃)₂}₂(μ-pmtz)](ClO₄)₂ (2), where pmtz is 3-(2-pyrimidinyl)-1,2,4-triazine, have been synthesized and characterized. Single-crystal X-ray diffraction analysis reveals that the pmtz acts as a bidentate ligand in complex 1, whereas in complex 2 the pmtz coordinates as a bis-bidentate chelate, assembling two identical {Cu(PPh₃)₂} moieties into a copper(I) dimer with a triple-decker sandwich structure involving phenyl/pmtz/phenyl π–π interactions. The UV–vis spectra of complexes 1 and 2 show low-energy absorptions at 350–550 nm, assigned to the Cu(I) to pmtz MLCT transition, probably mixed with some XLCT character for 1. The absorption of 2 is blue-shifted relative to that of 1 due to the substitution of the iodide of 1 with the π-acceptor ligand PPh₃. Complexes 1 and 2 are non-emissive, both in solution and in the solid state, most likely owing to the electronic effects induced by the additional nitrogen donor of pmtz compared to 2,2′-bipyrimidine.     

Synthesis and X-ray structures of some mono- and binuclear ruthenium complexes with bisphosphine ligands

Summary The dinuclear complexes {RuCp*(-Cl)}₂(-dppm) (1) and {RuCp*(-Cl)}₂ (-dppe) (3) are obtained by reacting [RuCp*(³-Cl)]₄ withdppm, anddppe, respectively.1 is readily oxidized with AgCF₃SO₃, instead of chloride abstraction, to afford the dinuclear complex [{RuCp*(-Cl)}₂(-dppm)](SO₃CF₃)₂ (2) with two metal centers connected by a single Ru-Ru bond. Under the same conditions,3 decomposes to several intractable materials. Similarly to1, RuCp* (dmpe)Cl reacts with AgCF₃SO₃ to afford the Ru(III) complex [RuCp*(dmpe)Cl](SO₃CF₃) (4) without no halide abstraction. The crystal structures of2,3, and4 are presented.

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Synthese und Röntgenstrukturanalyse einiger ein- und zweikerniger Rutheniumkomplexe mit Bisphosphinliganden

Zusammenfassung Die Komplexe {RuCp*(-Cl)}₂(-dppm) (1) und {RuCp*(-Cl₂(-dppe) (3) wurden durch Umsetzung von [RuCp*(³-Cl)]₄ mitdppm bzw.dppe dargestellt.1 wird durch AgCF₃SO₃ zum zweikernigen Komplex [{RuCp*(-Cl)}₂(-dppm)](SO₃CF₃)₂ (2) oxidiert, welcher eine Ru-Ru-Metallbindung aufweist. Unter den gleiche Reaktionsbedingungen zersetzt sich3 zu undefinierten Produkten. Analog zu1 reagiert RuCp* (dmpe)Cl mit AgCF₃SO₃ zum Ru(III)-Komplex [Ru(Cp*)(dmpe)Cl](SO₃CF₃) (4) wobei es zu keiner Chloridabspaltung kommt. Von2,3, und4 wurden die Kristallstrukturen bestimmt.

     

Coordination chemistry of di-2-pyridylketone. Synthesis, spectroscopic investigations, X-ray studies and DFT calculations of Re(III) and Re(V) complexes

The paper presents a combined experimental and computational study of Re(III) and Re(V) complexes containing di-2-pyridylketone and its gem-diol form – [ReCl₃(dpk-N,O)(PPh₃)] (1), [ReCl₃(dpk-N,N′)(OPPh₃)] (2) and [ReOBr₃(dpk-OH)]·2(dpkH⁺Br⁻) (3). All the complexes have been characterized spectroscopically and structurally (by single-crystal X-ray diffraction). The complex 2 has been additionally studied by magnetic measurement. The magnetic behavior of 2 is characteristic of mononuclear octahedral Re(III) complex with d⁴ low-spin (³T_1g ground state) and arise because of the large spin–orbit coupling (ζ = 2500 cm⁻¹), which gives diamagnetic ground state. DFT and time-dependent (TD)DFT calculations have been carried out for [ReCl₃(dpk-N,N′)(OPPh₃)] and [ReOBr₃(dpk-OH), and their UV–vis spectra have been discussed on this basis.     

Four mono-/bi-nuclear palladium(II) complexes of triphenylphosphine and heterocyclic-N/NS ligands: Synthesis, structural characterization and luminescence properties

The reactions of palladium(II) chloride, PPh₃ and heterocyclic-N/NS ligand in a mixture of CH₃CN (5 ml) and CH₃OH (5 ml) produced [PdCl₂(PPh₃)(L1)]·(CH₃CN) (1) (L1 = ADMT = 3-amino-5,6-dimethyl-1,2,4-triazine), [PdCl₂(PPh₃)(L2)] (2) (L2 = 3-CNpy = 3-cyanopyridine), [PdCl(PPh₃)(L3)]₂·(CH₃CN) (3), [PdCl(PPh₃)₂(HL3)]Cl (4) (HL3 = Hmbt = 2-mercaptobenzothiazole). The coordination geometry around the Pd atoms in these complexes is a distorted square plane. In 3, L3 acts as a bidentate ligand, bridging two metal centers, while in 4, HL3 appears as monodentate ligand with one nitrogen donor atom uncoordinated. Complexes 1-4 are characterized by IR, luminescence, NMR and single crystal X-ray diffraction analysis. All complexes exhibit luminescence in solid state at room temperature.     

Synthesis and structural characterization of two cationic dinuclear cymene-ruthenium(II) complexes with thiolato and chloro bridges

Treatment of [(p-cymene)RuCl₂]₂ with HSp-Tol or HSCH₂Ph in the presence of K[PF₆] gave the cationic dinuclear cymene–ruthenium(II) complexes [(p-cymene)₂Ru₂(μ-Cl)(μ-Sp-Tol)₂][PF₆] (1) and [(p-cymene)₂Ru₂(μ-Cl)(μ-SCH₂Ph)₂][PF₆] (2), respectively, which have been characterized by IR, NMR spectroscopies and mass spectrometry along with microanalyses. Their crystal structures were determined by single-crystal X-ray diffraction analyses. The structures of the cationic complexes contain the unusual pseudo-trigonal-bipyramidal Ru₂S₂Cl framework without a ruthenium–ruthenium single bond. The two p-cymene–ruthenium units are held together by two bridging thiolates and one bridging chloride.     

Synthesis, characterization and reactivity of some novel dinuclear mixed-ligand peroxouranium(VI) complexes

Novel anionic dinuclear mixed-ligand peroxo complexes of the type [(UO₂)₂(O₂)₃L(H₂O)₂]³⁻ (L = Histidinate, aspartate, salicylate, Imidazolate and glutamate) have been synthesized from the interaction of uranyl ion (UO₂²⁺) with peroxide (O₂²⁻) in the presence of the respective coligand (L) at pH 9–10. The sparingly soluble complexes were characterized by elemental analyses, FT-IR, laser Raman (LR) and UV-vis spectroscopy and solution electrical conductance measurements. Based on these studies, a double bridged dinuclear structure involving one peroxo and the mixed ligand L (via-COO⁻) has been tentatively proposed. Infra-red coupled with LR spectra evidenced structurally different metal bound peroxides (ν² and σ:σ). An aqueous solution of the salicylate and aspartate complexes have been shown to convert triphenylphosphine (PPh₃), cyclohexene, styrene and SO₂ to the corresponding OPPh₃, 1,2 cyclohexanediol, phenylethyleneglycol and SO₄²⁻, respectively.