Beiträge zur Komplexchemie der Phosphine und Phosphinoxide. XXII. FeII-, CoII-, NiII- und CuII-Komplexe des 8-Chinolyl-diphenylphosphins

Complex compounds of the general composition [(CDPP₂)MX]X (M = Fe, Co, Ni; X = Cl, Br) and [CDPPCuX]₂X₂ are formed by the reaction of the chelate ligand 8-quinol-diphenylphosphine (CDPP) with anhydrous salts of Fe^II Co^II Ni^II and Cu^II in acetone. According to magnetic and spectroscopic measurements the complexes of Fe and Ni represent a type with the coordination number five whereas in the complexes of Co there exists an equilibrium between complexes with tetrahedral and five coordination. The two-nuclear complexes of Cu show μ-halide bridges and a Cu? Cu-correlation.     

Rhodium complexation with phosphoryl-containing calix[4]resorcine

Complexation of rhodium compounds with phosphoryl-containing calix[4]resorcine in ethanol and acetone has been considered. The structure and properties of the synthesized complexes have been studied by IR and Raman spectroscopy, ¹H and ³¹P NMR, EPR, UV-Vis spectroscopy, and TG/DSC. The effect of the solvent nature and conformation of a macrocyclic ligand on the structure of the resulting complexes has been observed. It has been demonstrated that one of the key factors responsible for complexation in EtOH is self-association of the ligand without the participation of the solvent. Complex formation in acetone is determined by its high ionizing ability. In diamagnetic complexes, the macrocyclic ligand is coordinated to the central atom through the phosphoryl oxygen atoms. For triaquatrichlororhodium in an aprotic medium, coordination occurs through the oxygen atoms of resorcinol moieties, which is accompanied by the formation of resorcinol radical anion and conversion of the diethoxyphosphorylaryl groups into ethoxyhydroxyphosphorylaryl moieties.     

Transition metal(II) ions with dinegative tetradentate schiff base

Some new coordination polymers of Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II), obtained from the interaction of metal acetate with dipotassium salt of N,N’-di(carboxyethylidene)terephthalaldehydediimine (K₂SB) are described. The products, which have been characterized by elemental analyses, magnetic measurements, thermogravimetric analyses, electronic and infrared spectral studies, have composition, [M(SB)(H₂O)₂]_n. These colored coordination polymers are non-hygroscopic and quite stable at room temperature. On the basis of analytical data and IR studies, a 1:1 metal to ligand stoichiometry has been suggested to these coordination polymers. The IR studies have also revealed that ligands are coordinated to metal ion through carboxy oxygen and azomethine nitrogen. All the studies suggested tetradentate nature of the ligand with octahedral symmetry of the coordination polymers. All the coordination polymers are insoluble in acetone, ethanol, chloroform, methanol, benzene, DMF and DMSO. The thermal decomposition of the coordination polymers is studied and indicates that not only the coordinated water is lost but also that the decomposition of the ligand from the coordination polymers is necessary to interpret the successive mass loss.     

The study of Gd<Superscript>3+</Superscript> complexation with 4-dihydroxyboropenylalanine in aqueous solutions

The process of Gd³⁺ complexation with 4-dihydroxyborophenylalanine (DHBPA) in aqueous solutions was studied by the contact conductometry, IR, and X-ray photoelectronic spectroscopy methods. The complex formation reactions of Gd³⁺ with DHBPA were found to occur in steps, depending on the metal: ligand ratio. In the final reaction product, i.e., the chelate complex [Gd(DHBPA)₃], each molecule of a ligand occupies two coordination sites.     

Microstructure and thermal analysis of lithium ferrite pre-milled in a high-energy ball mill

The synthesis and thermal and spectroscopic studies of a new Co^II–Fe^III heteropolynuclear coordination compound are presented. The in situ oxidation product of ethylene glycol plays the role of ligand. Under specific working conditions, the reaction of ethylene glycol with Fe^III and Co^II nitrates in dilute acid solutions occurs with the oxidation of the former to glyoxylic acid, coordinated to the Co^II and Fe^III cations as glyoxylate anion (C₂H₂O₄ ^2?), with simultaneous isolation of the heteropolynuclear coordination compound. In order to separate and identify the ligand, the synthesized coordination compound, having the composition formula Co₄Fe₁₀(L)₉(OH)₂₀(H₂O)₃₂·14H₂O, where L is the glyoxylate anion, has been treated with R–H cationite (Purolite C-100). After the retention of the metal cations, the resulting glyoxylic acid was confirmed by measuring its physical constants, by specific reactions and through spectroscopic methods. The synthesized coordination compound was characterized by physical–chemical analysis, electronic spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD) and thermal analysis. Cobalt ferrite impurified with ferric oxide was obtained following the thermal decomposition of Co^II–Fe^III polyhydroxoglyoxylate. The oxides obtained through thermolysis were studied by FTIR, XRD, scanning electron microscopy (SEM) and elemental analysis.     

Adventitious formation of a new oxopentadienyl Mn(I) tricarbonyl complex: Structural study and bonding investigation of (η-CH2C(Fc)CHC(Fc)O)Mn(CO)3

A Mn(I) tricarbonyl complex of a 1,3-diferrocenyl-1-oxopentadienyl ligand was synthesised adventitiously by what seems to be an in-situ aldol-like condensation of two acetylferrocene units promoted by benzyl-Mn(CO)₅. X-ray structural analysis of this unexpected product confirms the η⁵ coordination of the 1,3-diferrocenyl-1-oxopentadienyl ligand to the Mn(CO)₃ moiety. The nature of the metal-ligand bonding relationship was studied by theoretical calculations; it outlines the charge unbalance (polarisation) at the oxopentadienyl moiety as well as the lack of ketone character of the latter Mn-bound ligand.     

Synthesis,pyrolytic and bioassay studies of complexes Ni(II), Cu(II) and Zn(II) bromides with a chelating ligand of N,N donor sites

Coordination complexes of modified hydrazine are prepared with Ni(II), Cu(II), and Zn(II) metal ions. The ligand is synthesized by removing the methoxy moiety of methyl anthranilate with nitrogen of hydrazine hydrate, creating new coordination site. The coordination complexes are synthesized by reacting the ABH ligand with dehydrated M(II) [Cu²⁺, Zn²⁺ and Ni²⁺] bromide in an inert environment. The structures of the coordination complexes are elucidated basing on the physical measurements including elemental analysis, NMR, IR, UV–Vis spectra, magnetic and conductance measurements. These results reflect the M(ABH)Br₂ composition of the corresponding complexes. Thermal studies show the Irving William trend for the stability of complexes. Antibacterial activities and antifungal studies are also carried out in order to investigate the biological activity upon complexation.     

Thermochemistry of formation of copper(II)-ethylenediamine complexes and solvation of reagents in aqueous organic solvents

The heat effects of the reactions of formation of ethylenediamine-copper(II) complexes were determined calorimetrically in mixtures of water with ethanol, acetone and dimethylsulfoxide. The results were interpreted in terms of the enthalpies of transfer (Δ_t H ⁰) of the complex former, the ligand and the complex ion from water to binary solvents. In water—DMSO mixtures, the Δ_t H ⁰ values for copper(II) and complex ions were found to change in similar ways, and their contributions to the reaction heat effects compensate each other to a large extent. Thus, the reaction enthalpy change due to solvent composition variation is caused mainly by the changes in ligand solvation enthalpies. In aqueous ethanol and acetone solutions, the changes in Δ_t H ⁰ for all reagents influence the heat effect equally.     

Ligand Design for Site‐Selective Metal Coordination: Synthesis of Transition‐Metal Complexes with η6‐Coordination of the Central Ring of Anthracene

A polycyclic aromatic ligand for site‐selective metal coordination was designed by using DFT calculations. The computational prediction was confirmed by experiments: 2,3,6,7‐tetramethoxy‐9,10‐dimethylanthracene initially reacts with [(C₅H₅)Ru(MeCN)₃]BF₄ to give the kinetic product with a [(C₅H₅)Ru]⁺ fragment coordinated at the terminal ring, which is then transformed into the thermodynamic product with coordination through the central ring. These isomeric complexes have markedly different UV/Vis spectra, which was explained by analysis of the frontier orbitals. At the same time, the calculations suggest that electrostatic interactions are mainly responsible for the site selectivity of the coordination.     

Ligand Design for Site-Selective Metal Coordination: Synthesis of Transition-Metal Complexes with η6-Coordination of the Central Ring of Anthracene

A polycyclic aromatic ligand for site-selective metal coordination was designed by using DFT calculations. The computational prediction was confirmed by experiments: 2,3,6,7-tetramethoxy-9,10-dimethylanthracene initially reacts with [(C₅H₅)Ru(MeCN)₃]BF₄ to give the kinetic product with a [(C₅H₅)Ru]⁺ fragment coordinated at the terminal ring, which is then transformed into the thermodynamic product with coordination through the central ring. These isomeric complexes have markedly different UV/Vis spectra, which was explained by analysis of the frontier orbitals. At the same time, the calculations suggest that electrostatic interactions are mainly responsible for the site selectivity of the coordination.     

A New Two‐Dimensional Coordination Polymer of Mercury(II) with very High Thermal Stability

A 2D Hg^II coordination polymer containing ligands 1,2,4‐triazole (Htrz) and thiocyanate, [Hg(μ₃‐trz)(SCN)]_n ( 1 ) has been synthesized and characterized by elemental analysis and IR spectroscopy. The single‐crystal X‐ray data show the coordination number of Hg atoms is four and the ligand trz^? acts as a three‐fold donor. The thermal stability of compound 1 was studied by thermal gravimetric and differential thermal analyses. The composition and formation of the complex in methanol solution were found to be in support of its solid state structure.     

A stable binuclear complex containing PdHPd bonds

The preparations of the binuclear hydrido-bridged cations [(terdentate ligand)Pd(μ-H)Pd(terdentate ligand)]⁺ from [(terdentate ligand)Pd(acetone)]⁺ and NaO₂CH and [(terdentate ligand)Pd(μ-H)Pt(terdentate ligand)]⁺ from [(terdentate ligand)Pd(acetone)]⁺ and [(terdentate ligand)PtH] (terdentate ligand = 2,6-(Ph₂PCH₂)₂C₆H₃) are reported. The preparation of the cation [(terdentate ligand)Pt(μ-H)Pt(terdentate ligand)]⁺ is also reported.     

A five-coordinate complex of copper chloride with 2-amino-5-ethyl-1,3,4-thiadiazole

A complex of Cu(II) chloride with 2-amino-5-ethyl-1,3,4-thiadiazole (AET) was prepared, and its structure was studied by IR spectroscopy and single crystal X-ray diffraction. The complex has the composition CuCl₂(AET)₄. The coordination sphere of the copper atom includes four molecules of the heterocyclic ligand coordinated via N atoms of thiadiazole rings and one of Cl^? anions; the second Cl^? anion is in the outer sphere.     

Synthesis and biological studies of complexes of 2- amino-<Emphasis Type="Italic">N</Emphasis>(2-aminobenzoyl) benzohydrazide with Co(II), Ni(II), and Cu(II)

The present work is concerned with the synthesis and coordination compounds of 2-amino-N(2-aminobezoyl) benzohydrazide (ABH). The ligand was synthesized by the reaction of methylanthranilate and hydrazine in 2:1 molar ratio. It can be viewed as a modified form of hydrazide. The ligand was characterized by ¹H-NMR, ¹³C-NMR, mass spectrometry, elemental analysis, and infrared studies. The ligand has got -NH₂ moeity, the site for chelation. The complexes of Co(II), Ni(II), and Cu(II) chlorides and bromides were prepared. These complexes were characterized by elemental analysis, infrared, conductance, and magnetic susceptibility studies. Infrared spectra studies confirmed the formation of complexes, while elemental studies suggested the complexation of [M(ABH)X₂] (where X = Cl⁻ or Br⁻) composition.     

A Remarkable cis‐ and trans‐Spanning Dibenzylidene Acetone Diphosphine Chelating Ligand (dbaphos)

A multidentate and flexible diolefin–diphosphine ligand, based on the dibenzylidene acetone core, namely dbaphos ( 1 ), is reported herein. The ligand adopts an array of different geometries at Pt, Pd and Rh. At Pt^II the dbaphos ligand forms cis‐ and trans‐diphosphine complexes and can be defined as a wide‐angle spanning ligand. ¹H NMR spectroscopic analysis shows that the β‐hydrogen of one olefin moiety interacts with the Pt^II centre (an anagostic interaction), which is supported by DFT calculations. At Pd⁰ and Rh^I, the dbaphos ligand exhibits both olefin and phosphine interactions with the metal centres. The Pd⁰ complex of dbaphos is dinuclear, with bridging diphosphines. The complex exhibits the coordination of one olefin moiety, which is in dynamic exchange (intramolecular) with the other “free” olefin. The Pd⁰ complex of dbaphos reacts with iodobenzene to afford trans‐[Pd^II(dbaphos)I(Ph)]. In the case of Rh^I, dbaphos coordinates to form a structure in which the phosphine and olefin moieties occupy both axial and equatorial sites, which stands in contrast to a related bidentate olefin, phosphine ligand (“Lei” ligand), in which the olefins occupy the equatorial sites and phosphines the axial sites, exclusively.     

An interlocked coordination cage based on aromatic amide ligands

An interlocked M_4 L_8 coordination cage was synthesized by coordination-driven self-assembly of palladium(Ⅱ) ions with aromatic amide bidentate ligands.The reaction of the ligand and the metal at 2:1 ratio led to the monomeric M_2 L_4 cage as the kinetic product,while the thermodynamic product M_4 L_8 cage was obtained by prolongating the reaction.This conve rsion and the interlocked structure was clearly revealed by using ~1 H NMR,mass spectrometry and X-ray crystallography.The driving force of interlocking was mainly attributed to the interactions(hydrogen bonding,aromatic stacking and electrostatic interaction) arising from the aptitude of flexibility of the amide ligand.     

Bis{μ‐2‐[(1,5‐diaza‐1‐cyclooctyl)methyl]phenolato‐N,N′,O:O}bis[chlorozinc(II)] diacetone solvate: design of a square‐pyramidal ZnN2O2Cl complex

The title complex, [Zn₂(C₁₃H₁₉N₂O)₂Cl₂]·2C₃H₆O, resides on a crystallographic inversion center. The two Zn^II centers bridged by the phenoxo groups are in pentacoordinated distorted square‐pyramidal coordination environments with an intramolecular Zn?Zn distance of 3.175 (3) Å. The mesocyclic ligand takes a boat–chair conformation and an H atom from the 1,5‐di­aza­cyclo­octane ring effectively blocks the axial coordination site opposite the Cl ligand to form the ZnN₂O₂Cl geometry. The crystal structure is stabilized by a N—H?O hydrogen bond between the amino group and an acetone mol­ecule.     

Chemical, spectroscopic characterization, DFT studies and initial pharmacological assays of a silver(I) complex with N-acetyl-l-cysteine

A new silver(I) complex with N-acetyl-l-cysteine (NAC) of composition AgC₅H₈NO₃S·H₂O was synthesized and characterized by a set of chemical and spectroscopic measurements. Solid-state ¹³C nuclear magnetic resonance (SSNMR) and infrared (IR) analyses indicate the coordination of the ligand to Ag(I) through the sulfur atom. The Ag-NAC complex is slightly soluble in dimethyl sulfoxide. It is insoluble in water, methanol, ethanol, acetone and hexane. Antibacterial activity of the silver complex with N-acetyl-l-cysteine (Ag-NAC) was evaluated by antibiogram assays using the disc diffusion method. The compound showed an effective antibacterial activity against Staphylococcus aureus (Gram-positive), Escherichia coli and Pseudomonas aeruginosa (Gram-negative) bacterial cells. Biological analysis for evaluation of a potential cytotoxic effect of Ag-NAC was performed using HeLa cells derived from human cervical adenocarcinoma. The complex presented a significant cytotoxic activity, inducing 80% of cell death at a concentration of 200 μmol L⁻¹.     

New fluorescent compounds based on zinc thiocyanate: influence of structure on spectral properties

New coordination compounds based on zinc thiocyanate, namely (acetone thiosemicarbazone‐κ²N ¹,S )bis(isothiocyanato‐κN )zinc(II) monohydrate, [Zn(NCS)₂(C₄H₉N₃S)]·H₂O, (I), and diaquatetrakis(urea‐κO )zinc(II) tetrakis(isothiocyanato‐κN )zinc(II), [Zn(CH₄N₂O)₄(H₂O)₂][Zn(NCS)₄], (II), were synthesized and studied by UV–Vis, fluorescence and IR spectroscopy. Coordination salt (II) forms a rare system composed of two different coordination units of the same metal and it is the first example of a compound with two completely different zinc coordination units, of which one contains a tetrakis(urea)zinc unit. Both (I) and (II) possess fluorescence properties and produce blue and green emissions, respectively, upon irradiation with violet light. The spectral properties were correlated with the observed molecular and supramolecular structures. The acetone thiosemicarbazone ligand of (I) exhibits (upon coordination) red shifts of bands corresponding to N=C and C=S stretching vibration frequencies, which is not typical for chelating molecules.     

Mechanistic insights into photochromic behavior of a ruthenium(II)-pterin complex

The pterin‐coordinated ruthenium complex, [Ru^II(dmdmp)(tpa)]⁺ ( 1 ) (Hdmdmp=N,N‐dimethyl‐6,7‐dimethylpterin, tpa=tris(2‐pyridylmethyl)amine), undergoes photochromic isomerization efficiently. The isomeric complex ( 2 ) was fully characterized to reveal an apparent 180° pseudorotation of the pterin ligand. Photoirradiation to the solution of 1 in acetone with incident light at 460 nm resulted in dissociation of one pyridylmethyl arm of the tpa ligand from the Ru^II center to give an intermediate complex, [Ru(dmdmp)(tpa)(acetone)]²⁺ ( I ), accompanied by structural change and the coordination of a solvent molecule to occupy the vacant site. The quantum yield (?) of this photoreaction was determined to be 0.87 %. The subsequent thermal process from intermediate I affords an isomeric complex 2 , as a result of the rotation of the dmdmp^2? ligand and the recoordination of the pyridyl group through structural change. The thermal process obeyed first‐order kinetics, and the rate constant at 298 K was determined to be 5.83×10^?5 s^?1. The activation parameters were determined to be ΔH^≠=81.8 kJ mol^?1 and ΔS^≠=?49.8 J mol^?1 K^?1. The negative ΔS^≠ value indicates that this reaction involves a seven‐coordinate complex in the transition state (i.e., an interchange associative mechanism). The most unique point of this reaction is that the recoordination of the photodissociated pyridylmethyl group occurs only from the direction to give isomer 2 , without going back to starting complex 1 , and thus the reaction proceeds with 100 % conversion efficiency. Upon heating a solution of 2 in acetonitrile, isomer 2 turned back into starting complex 1 . The backward reaction is highly dependent on the solvent: isomer 2 is quite stable and hard to return to 1 in acetone; however, 2 was converted to 1 smoothly by heating in acetonitrile. The activation parameters for the first‐order process in acetonitrile were determined to be ΔH^≠=59.2 kJ mol^?1 and ΔS^≠=?147.4 kJ mol^?1 K^?1. The largely negative ΔS^≠ value suggests the involvement of a seven‐coordinate species with the strongly coordinated acetonitrile molecule in the transition state. Thus, the strength of the coordination of the solvent molecule to the Ru^II center is a determinant factor in the photoisomerization of the Ru^II–pterin complex.