Electrochemical Studies of Ternary Complexes of Cd(II) with Promethazine and Glutamic Acid

Abstract

The ternary complexes of Cd(II) with promethazine and glutamic acid have been studied polarographically. The stability constants of the formed complexes have been calculated using the suitable methods. The results reveal the formation of two ternary complexes, Cd(Glu) (Pro), and Cd(Clu)₂ (Pro) with stability constants of 7.4 and 9.22 (log K), respectively.     

Interaction of Cu(I) carbonyl with Pd(II) and Cu(II) complexes in aqueous and nonaqueous media

CO hydrogenation over Ni-rutile and Ni-anatase catalysts has been studied at 470–520 K. Activity of the rutile catalyst is by an order of magnitude higher and it produces C₁–C₁₅-hydrocarbons; the anatase sample yields only C₁–C₃-paraffins. At 310–330 K the Ni-anatase catalyst loses nickel, while the nickel content in the Ni-rutile sample remains practically unchanged.

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CO - 470–520 , ; C₁–C₁₅; — C₁–C₃. 310–330 - , .

     

Pnictogen-thiacrown complexes with Pt(II) and Pd(II)

Platinum(II) and palladium(II) complexes of the trithiacrown [9]aneS(3) containing a range of Group 15 donors are reviewed. These complexes have the general formula [M([9]aneS(3))(L(2))](n+) where L represents at least one Group 15 donor. Complexes involving pnictogens, with the exception of bismuth, are observed. The complexes generally have an elongated square pyramidal geometry with a long distance interaction to the third sulphur of the [9]aneS(3) which forms the apex of the square pyramid. This axial metal-sulphur distance is quite sensitive to the donor properties of L. Poorer donors such as Sb and As ligands show short axial distances whereas the better N donor ligands show longer distances. Pt(II) complexes of the formula [Pt([9]aneS(3))(EPh(3))(2)](2+) (E = P, As, Sb) show a considerable distortion towards a trigonal bipyramidal geometry due to intramolecular π-π interactions. Over seventy of these types of complexes have been crystallographically characterized and are discussed in this article. Other unique features of the complexes, including NMR spectroscopy, redox chemistry, and electronic spectroscopy, are also discussed.     

Pd(II)- and Pd(0)-cocatalyzed reactions of sulfonamides with MCPs

[reaction: see text] MCPs can efficiently react with sulfonamides in the presence of Pd(0) and Pd(II) catalysts to give the corresponding ring-opened products in high yields.     

Interaction of Silver(II) and Gold(III) meso-Tetraphenylporphine Complexes with Concentrated Sulfuric Acid

The reaction of meso-tetraphenylporphine (H₂TPP) with Ag(OAc) or KAuCl₄in boiling acetic acid affords Ag^IITPP and (Cl)Au^IIITPP complexes. The complexes are purified by column chromatography and identified by thin layer chromatography and IR and electronic absorption spectroscopy. The transfer of a proton to the porphyrin macrocycle and dissociation of the complexes via the metal–nitrogen bonds in concentrated H₂SO₄at different temperatures and H₂SO₄concentrations are studied by spectrophotometric and kinetic methods. The formation of the stable ion-molecular H-associate of the metalloporphyrin with a doubly-charged metal cation is found for the first time for silver(II) tetraphenylporphine. Gold(III) tetraphenylporphine exists in a sulfuric acid solution in the monomolecular form. The numeric values of true rates and activation parameters of the complex dissociation are determined. The stability, state in solution, and mechanism of dissociation of the silver(II) and gold(III) tetraphenylporphine complexes are determined by the metal electronic configuration of the complex cation and, especially, by the contribution of the component to the donor–acceptor M–N interaction.     

Complexes of Cysteine and Cysteinemethylester with Pd(II) and Pt(II)

The reactions of Cysteine hydrochloride (CysHCl) and Cysteinemethylester hydrochloride (OMeCysHCl) with K₂MX₄ or PdCl₂, where M:Pd(II), Pt(II) and X:Cl, Br have been studied in acidic, neutral and alkaline aqueous solutions. The isolated complexes are of 1:1 and 1:2 metal to ligand ratio as their elemental analyses show. They correspond to the formulae: M(Cy⁻)₂, M(Cys)₂X₂, (MCys⁻X)₂, M(OMeCy⁻)₂, M(OMeCys)₂X₂, [M(OMeCys⁻)X]₂ and (MCys²⁻)_n. Possible structures of the isolated complexes are suggested and discussed with respect to their IR spectra. The results indicate that the coordination sites strongly depend upon the pH of the solutions and the stoichiometry of the metal to ligand ratio.     

New Pd(II) fluorides

Single crystals of CsPd₂F₅ (orange-brown, ImmaD²⁸_2h, No. 74; Z = 2; a = 6.53₃, b = 7.86₂, c = 10.79 ā)have been obtained (instead of ‘CsPdF₃’) by heating mixtures of CsF and PdF₂ (ratio 1:1) in sealed gold tubes (under dry Ar) up to t ≈ 600°C (20–3O d). The structure is related closely to the CsAgFeF₆-type of structure [1], but, because of the ‘absence’ of one F^?, one half of the Pd²⁺-ions is coordinated planar quadratically, the other half octehedrally. From Guinier data are isotypic Me^IPd₂F₅ (Me^I  K, Rb, Tl), brown and CsMe^IIPdF₅ (Me^II  Zn, Cd, Ni, Co, Mg), brown or yellow.Under similar conditions single crystals of Rb₃PdF₅ (yellow, P4/mbm-D⁵_4h, No. 127; Z = 2, a = 7.46₇, c = 6.49₇ ā) have been obtained (instead of ‘Rb₂PdF₄’) by heating mixtures of RbF and PdF₂ (ratio 2:1) in sealed gold tubes (under dry Ar) up to t ≈ 560°C (20–30 d). The coordinationnumber of Pd²⁺ is C.N. = 4 (planar quadratic). Isotypic are (single crystal data) Cs₃PdF₅, Rb₂CsPdF₅ (with ordered distribution of Rb, Cs) and K₃PdF₅, all yellow.     

Complexes of hydroxamates X. Interaction of methioninehydroxamic acid with Ni(II) and Pd(II). Kinetics and reaction mechanism

The kinetic stopped flow method has been used to study the reaction rates of Ni(II) and Pd(II) with methioninehydroxamate (MX). Two reaction rates were observed in the MX? Ni(II) system whereas three rates were observed in the MX? Pd(II) system. Most of the rate steps were dependent on pH as well as on T_MX (total concentration of methioninehydroxamate). The observed pseudo-first-order rate constants at constant pH are expressed empirically as k = m_i + m′_i T_MX. The parameters m_i and m′_i are pH-dependent. It has been concluded that hydroxy metal species contributed to the explanation of the rate of the metal complexation with MX. Similar systems have been correlated with the systems of current work. © 1995 John Wiley & Sons, Inc.     

Selective Sorption of Pd(II) from Nitric-Nitrous Acid Solutions Simulating PUREX Raffinates with Polymethylene Monosulfide

Static sorption of Pd(II) from nitric and nitric-nitrous acid solutions, simulating PUREX raffinates, with laboratory and semicommercial samples of polymethylene monosulfide is studied. The selectivity of Pd(II) recovery from the simulated solutions is determined.     

Application of a Glassy Carbon Electrode Modified with Poly(Glutamic Acid) in Caffeic Acid Determination

Glassy carbon electrodes were coated with films of poly(glutamic acid) (PG), and the modified electrode proved to be very effective in the oxidation of caffeic acid. The performance of the film was also tested with ascorbic acid, coumaric acid, ferulic acid, sinapic acid and chlorogenic acid. At pH 5.6, all the hydroxycinnamic acids yield a higher peak current intensity when oxidized after incorporation in the PG-modified electrode, and only the oxidation of ascorbic acid exhibits overpotential reduction. At pH 3.5 only caffeic and chlorogenic acid are incorporated in the modified electrode and exhibit a well-defined oxidation wave at +0.51 V and +0.48 V, which is the base for their determination. Linear calibration graphs were obtained from 9 × 10⁻⁶ mol L⁻¹ to 4 × 10⁻⁵ mol L⁻¹ caffeic acid by linear voltammetric scan and from 4 × 10⁻⁶ mol L⁻¹ to 3 × 10⁻⁵ mol L⁻¹ by square wave voltammetric scan. The method was successfully applied to the determination of caffeic acid in red wine samples without interference from other hydroxycinnamic acids or ascorbic acid.     

Spectrophotometric Determination of Thioctic Acid in its Dosage Forms through Complex Formation with Pd(II)

A simple and sensitive spectrophotometric method has been developed for the determination of thioctic acid in pharmaceutical preparations. The proposed method is based upon the formation of a complex with palladium(II) in acetate buffer of pH 4.8 with an absorption maximum at 318 nm. The absorbance obeyed Beer's law over the range of 2–20 μg mL^?1 with a minimum detection limit of 0.15 μg mL^?1 and molar absorptivity (ζ) of 7 × 10³ L mol^?1.cm^?1. The different experimental parameters affecting the development and stability of the color were carefully studied and optimized. The proposed method was successfully applied to the analysis of commercial tablets and ampoules. The results obtained were in good agreement with those obtained using a reference spectrophotometric method. A proposal of the reaction pathway is presented.     

Cyclometallated Pt(II) and Pd(II) complexes with a trithiacrown ligand

We report the synthesis and full characterization for a series of cyclometallated complexes of Pt(II) and Pd(II) incorporating the fluxional trithiacrown ligand 1,4,7-trithiacyclononane ([9]aneS3). Reaction of [M(C insertion mark N)(micro-Cl)]2 (M = Pt(II), Pd(II); C insertion mark N = 2-phenylpyridinate (ppy) or 7,8-benzoquinolinate (bzq)) with [9]aneS3 followed by metathesis with NH4PF6 yields [M(C insertion mark N)([9]aneS3)](PF6). The complexes [M(C insertion mark P)([9]aneS3)](PF6) (M = Pt(II), Pd(II); Cinsertion markP = [CH2C6H4P(o-tolyl)2-C,P]-) were synthesized from their respective [Pt(C insertion mark P)(micro-Cl)]2 or [Pd(C insertion mark P)(micro-O2CCH3)]2 (C insertion mark P) starting materials. All five new complexes have been fully characterized by multinuclear NMR, IR and UV-Vis spectroscopies in addition to elemental analysis, cyclic voltammetry, and single-crystal structural determinations. As expected, the coordinated [9]aneS3 ligand shows fluxional behavior in its NMR spectra, resulting in a single 13C NMR resonance despite the asymmetric coordination environment of the cyclometallating ligand. Electrochemical studies reveal irreversible one-electron metal-centered oxidations for all Pt(II) complexes, but unusual two-electron reversible oxidations for the Pd(II) complexes of ppy and bzq. The X-ray crystal structures of each complex indicate an axial M-S interaction formed by the endodentate conformation of the [9]aneS3 ligand. The structure of [Pd(bzq)([9]aneS3)](PF6) exhibits disorder in the [9]aneS3 conformation indicating a rare exodentate conformation as the major contributor in the solid-state structure. DFT calculations on [Pt([9]aneS3)(ppy)](PF6) and [Pd([9]aneS3)(ppy)](PF6) indicate the HOMO for both complexes is primarily dz2 in character with a significant contribution from the phenyl ring of the ppy ligand and p orbital of the axial sulfur donor. In contrast, the calculated LUMO is primarily ppy pi* in character for [Pt([9]aneS3)(ppy)](PF6), but dx2-y2 in character for [Pd([9]aneS3)(ppy)](PF6).     

Interaction of zinc(II) and manganese(II) with hemoglobin

In bis-tris buffer, pH 7.3, ZnCl₂ (1.5 × 10⁻³ M) increases the oxygen affinity of human adult hemoglobin (heme concentration 4 × 10⁻⁵ M) by 43%. Using an ion-exchange method involving ⁶⁵Zn radioisotope, we have found that Zn(II) forms a 1:1 complex with carboxyhemoglobin: K_f = 5.0 × 10⁵ M⁻¹ at room temperature. This strong binding of Zn(II) to hemoglobin is in line with the effect of the metal ion on oxygenation of hemoglobin. Mn(II) increases the oxygen affinity of hemoglobin only slightly below 25% oxygen saturation, and causes a decrease in oxygen affinity above 25% saturation (by 24 at 50% saturation). The binding of this metal ion with hemoglobin is much weaker than that found for zinc ion.     

Some complex combinations of Pd(II) with methionine

Seven new complexes of Pd(II) with methionine were synthesized and characterized by elementary analysis, thermogravimetry, UV and IR spectra. The thermogravimetric behaviour of these compounds indicates the formation of intermediates with probably sulphur and chlorine bridges; elementary analysis seems to confirm these conclusions.     

Hg(II)...Pd(II) metallophilic interactions

Reaction of bis(pentafluorophenyl)mercury (1) with the Pd(II) complexes [Pd(salophen)] (I, salophen = N,N'-disalicylidene-o-phenylenediaminate) and [Pd(N--C)(OAc)]2 (II, N--C = (2-(2-pyridyl)phenyl-C,N)) leads to the formation of the supramolecular complexes [1-(I)2] and [1-(II)2] in which the mercury synthon is sandwiched by two molecules of the palladium complex. These complexes, whose formation can be observed in solution by UV-vis spectroscopy, have been fully characterized. The short Hg-Pd distances of 3.2841(2) A in [1-(I)2] and 3.1065(8) A in [1-(II)2] indicate the presence of a Hg-Pd metallophilic interaction which, at least for [1-(II)2], is complemented by a Pd(II)-->Hg(II) donor-or component.     

Interaction of Gadolinium(III) with Nitrilotrimethylenephosphonic Acid

Interaction of gadolinium(III) with nitrilotrimethylenephosphonic acid is studied by potentiometry in wide range of concentration ratios and pH at 298.15 K and ionic strength of 0.1 (KNO₃). Logarithmic constants of protonation (logK _pr) are 7.88 ± 0.08 and 4.93 ± 0.05 for GdL^3– and GdHL^2–, respectively.