Thiosemicarbazone complexes of the platinum metals. A story of variable coordination modes

Salicylaldehyde thiosemicarbazone (H₂saltsc) reacts with [M(PPh₃)₃X₂] (M = Ru, Os; X = Cl, Br) to afford complexes of type [M(PPh₃)₂(Hsaltsc)₂], in which the salicylaldehyde thiosemicarbazone ligand is coordinated to the metal as a bidentate N,S-donor forming a four-membered chelate ring. Reaction of benzaldehyde thiosemicarbazones (Hbztsc-R) with [M(PPh₃)₃X₂] also affords complexes of similar type, viz. [M(PPh₃)₂(bztsc-R)₂], in which the benzaldehyde thiosemicarbazones have also been found to coordinate the metal as a bidentate N,S-donor forming a four-membered chelate ring as before. Reaction of the Hbztsc-R ligands has also been carried out with [M(bpy)₂X₂] (M = Ru, Os; X = Cl, Br), which has afforded complexes of type [M(bpy)₂(bztsc-R)]⁺, which have been isolated as perchlorate salts. Coordination mode of bztsc-R has been found to be the same as before. Structure of the Hbztsc-OMe ligand has been determined and some molecular modelling studies have been carried out determine the reason for the observed mode of coordination. Reaction of acetone thiosemicarbazone (Hactsc) has then been carried out with [M(bpy)₂X₂] to afford the [M(bpy)₂(actsc)]ClO₄ complexes, in which the actsc ligand coordinates the metal as a bidentate N,S-donorformingafive-membered chelate ring. Reaction of H₂saltsc has been carried out with [Ru(bpy)₂Cl₂] to prepare the [Ru(bpy)₂(Hsaltsc)]ClO₄ complex, which has then been reacted with one equivalent of nickel perchlorate to afford an octanuclear complex of type [Ru(bpy)₂(saltsc-H)₄Ni₄](ClO₄)₄.     

Solvent and salt effects on the redox behaviour of trisacetylacetonato manganese(III)

The polarographic and voltammetric behaviour of trisacetylacetonato manganese(III) [Mn(acac)₃] has been studied in methanol, ethanol, tetrahydrofurane, butyrolactone, propylenecarbonate, N,N-dimethylformamide, acetonitrile, nitromethane, N-methylpyrrolidone(2), 1,2-dichloroethane, dichloromethane, dimethylsulfoxide and acetic acid, Mn(acac)₃ was found to undergo a reversible one-electron reduction to Mn(acac)₃^? in most of the solvents mentioned. A further reduction at very negative potentials has been also observed in several solvents. The oxidation of Mn(acac)₃ to Mn(acac)₃⁺ has been studied by cyclovoltammetry in dichloromethane, nitromethane, acetonitrile, propylenecarbonate, N-methylpyrrolidinone(2), N,N-dimethylformamide and dimethylsulfoxide. The polarographic behaviour of NaMn(acac)₃ and Mn(acac)₂ has been investigated in the seven solvents listed above as well as in methanol. The half-wave potentials and the peak potentials referred to bisbiphenylchromium(I)/bisbiphenylchromium(0) as a reference redox system were found to vary with the nature of the solvent. Conductivity studies of Mn(acac)₃ and NaMn(acac)₃ have been carried out in these solvents. U.v.-visible and near i.r. spectra have been recorded of Mn(acac)₃, NaMn(acac)₃, Mn(acac)₂ and Na(acac) in the solvents mentioned. It has further been observed that the half-wave potentials for the polarographic reduction of Mn(acac)₃ shifted to more positive values by the addition of alkali metal ions and to more negative values by the addition of halide ions. The interactions of the solvent with Mn(acac)₃ and the variation of redox potentials with both the solvent and the added electrolytes will be discussed.     

X-ray K-absorption studies of cobalt(II) semicarbazones

X-ray K-absorption edges along with their extended X-ray absorption fine structure (EXAFS) have been recorded using a laboratory XAFS spectrometer for the cobalt(II) semicarbazones viz., Co(emsc)₂Br₂, Co(emsc)₂SO₄, Co(mchsc)₂Br₂, Co(mchsc)₂SO₄ and Co(mchsc)₂(NCS)₂. The chemical shifts for these samples have been reported. The total phase shifts δ₁ and phase parameters β₁ for these samples have been estimated using the modified graphical method for the determination of bond distances. The variations in the values of chemical shift, phase parameter β₁ and average metal–ligand bond distances have been explained. The total phase shift values for the complexes indicate a linear variation with wave vector k.     

Studies on the interactions of copper(II) chelate complexes with SO2

The reaction of bis (acetylacetonato) copper(II) with SO₂ yields CuSo₄ as a final product. Using e.p.r. technique mixed-ligand complexes of the type Cu(acac) (acacSO₂) have been detected at 100 K. The e.p.r. spectrum of the latter complex disappeared under passing argon through the sample. Lewis bases accelerated the reaction. No interaction of SO₂ with other complexes containing CuO₂N₂, CuN₂S₂, CuS₄ chromophores has been detected. In a common solution of Cu(acac)₂ and Cu(dtc)₂ the reaction proceeded only with Cu(acac)₂ though a mixed-ligand complex Cu(acac) (dtc) was formed. The addition of bases accelerated the reaction, all spectra disappeared and only Cu^I(dtc) has been found as a final product.     

Organometallic complexes with biological molecules. I. Diorganotin(IV)chloro protoporphyrin IX complexes: Solid-state and solution-phase characterization

Protoporphyrin IX (H₄PPIX) complexes of diorganotin(IV)chloro moieties with formula (R₂SnCl)₂H₂PPIX (R?Me, Bu and Ph) have been obtained and their solid-state and solution-phase configurations have been studied through spectroscopic investigations. Coordination of the side-chain carboxylates of H₄PPIX to R₂Sn(IV)Cl moieties, with bridging carboxylate (COO^?) has been inferred by comparison of the free and coordinated H₄PPIX IR spectra, while the occurrence of a five-coordinated tin(IV) atom in a cis-R₂ trigonal bipyramidal structure has been deduced, for all of the synthesized complexes, by rationalization of the nuclear quadrupole splitting parameters, according to the point-charge model formalism. Fanally, the solution-phase spectral features of (R₂SnCl)₂^?H₂PPIX are in agreement with the monomeric character of the protoporphyrin IX, under the experimental conditions used.     

Oxidation of Am(III) and stability of Am(IV) and Am(VI) in mineral acid solutions

The oxidation of americium in HNO₃, H₂SO₄ and HClO₄ solutions by a mixture of potassium persulfate with silver salt in the presence of potassium phosphotungstate has been investigated. The influence of acid and its concentration, of (NH₄)₂S₂O₃, K₁₀P₂W₁₇O₆₁ and silver salt on Am(III) oxidation rate, yield and stability of Am(IV) and Am(VI), has been studied. The complexation of Am(III), Am(IV) and Am(VI) with phosphotungstate ions has been investigated. It has been established that Am(III) and Am(IV) form ML₂ complexes and their apparent stability constants have been estimated. The oxidation mechanism is discussed. A method for preparing of Am(IV) in 0.1–6M HNO₃, O.1–3M H₂SO₄, 0.1–1M HClO₄ solutions is proposed. The oxidation of Am(III) to Am(IV) by KBrO₃ and K₂Cr₂O₇ in HNO₃, H₂SO₄, HClO₄ solutions in the presence of K₁₀P₂W₁₇O₆₁ has been investigated.     

Elektronentransferbarrieren als Funktion der Ligandenstruktur in CoN63+/CoN62+-Paaren Beziehungen zwischen der Struktur und der Redoxreaktivität

Electrontransfer Barriers in CoN₆³⁺/CoN₆²⁺ Couples as a Function of the Ligand Structure. Correlations between the Structure and Redoxreactivity The redox-reactivity of a series of CoN₆³⁺ complexes containing two saturated triamine ligands (open-chain and cyclic) has been systematically investigated. The perchlorate salts of 22 new amine complexes of the type [CoL₂]³⁺ and [CoLL′]³⁺, where L and L′ represent different coordinated triamines, have been synthesized, their electronic spectra have been recorded and the redoxpotentials of CoN₆^3+/2+ couples have been measured by use of cyclic voltammetry. The crystal structures of [Co(tacn)(dien)] I₃, [Co(tacn)(etdien)] I₃. H₂O, and of [Co(budien)₂]Br₃. H₂O (tacn = 1, 4, 7-triaza-cyclononane, dien = diethylenetriamine, etdien = N-(2-aminoethyl)-N-(ethyl)-1, 2-ethanediamine, budien = N-(2-aminoethyl)-N-(n-butyl)-1, 2-ethanediamine) have been determined by single crystal X-ray crystallography. The kinetics of the outer-sphere reductions of 14 CoN₆³⁺ complexes by [V(OH₂)₆]²⁺ have been measured and the electron transfer self-exchange rate constants of CoN₆^3+/2+ couples have been calculated by use of the Marcus equation. Structure-redox-activity correlations are discussed in the frame of the semiclassical Marcus-Sutin model.     

New oxorhenium complexes with the 8-quinolinolato ligand: X-ray structure and DFT calculations for [ReOBr(hqn)2]

The reactions of [ReO(OEt)X₂(PPh₃)₂] (X = Cl or Br) with 8-hydroxyquinoline (Hhqn) have been examined and the [ReOX(hqn)₂] complexes have been obtained. The crystal and molecular structures of [ReOBr(hqn)₂] have been determined. The electronic structure of [ReOBr(hqn)₂] has been calculated with the density functional theory (DFT) method, and additional information about binding in the ReO³⁺ unit has been obtained by NBO analysis. The spin-allowed electronic transitions of [ReOBr(hqn)₂] have been calculated with the time-dependent DFT method, and the UV–Vis spectra of the [ReOX(hqn)₂] compounds have been discussed on this basis.     

Studies on energetic compounds part 37: kinetics of thermal decomposition of perchlorate complexes of some transition metals with ethylenediamine

Five bis(ethylenediamine)metal perchlorate (BEMP) complexes like [M(en)₂](ClO₄)₂ (where M=Mn, Co, Ni, Cu, Zn and en=ethylenediamine) have been prepared and characterized by gravimetric methods, infrared spectroscopy (IR) and elemental analysis. Thermal decomposition studies have been undertaken using simultaneous thermogravimetry (TG) and differential thermal analysis (DTA) in nitrogen atmosphere. Non-isothermal TG and DTA studies have also been carried out separately in air to examine the effect of atmosphere on thermolysis of these complexes. Thermal stability of the complexes was found to decrease in the order: [Zn(en)₂](ClO₄)₂>[Mn(en)₂](ClO₄)₂>[Ni(en)₂](ClO₄)₂>[Cu(en)₂](ClO₄)₂>[Co(en)₂](ClO₄)₂.Isothermal TG over the temperature range of decomposition of all these complexes, has been done to evaluate the kinetics of decomposition. Both model fitting and model free isoconversional methods have been used to analyse the kinetics. Isoconversional method has been found to be superior over the conventional model fitting method and is able to describe the complex decomposition of these complexes. It indicates that the values of activation energy vary with the extent of conversion (α) while model fitting method results in a single value of E for overall decomposition process which cannot be attributed to any process under such a complex decomposition reaction. Explosion delay (D_E) measurement has been carried out to investigate the response of these complexes under the condition of rapid heating.     

Synthetic and structural studies of metal complexes derived from tris(3,5-bimethyl-pyrazolylmethyl)amine and pyridine derivatives

A series of metal complexes with a tripodal ligand, TMPzA, have been synthesized and characterized, and their single crystal structures have been determined by X-ray diffraction techniques. It has been found that when pyridyl derivatives as auxiliary ligands are added to the reaction mixture, the tripodal ligand TMPzA loses a pendant arm and coordinates with the metal centers to form the complexes: [Cu(DMPzA)(2,2′-bipy)]·(ClO₄)₂ (1), [(DMPzA)Cu(μ-4,4′-bipy)Cu(DMPzA)]·(ClO₄)₄ (2), [(TMPzA)Cu(μ-H₂DPC)Cu(DMPzA)]·(ClO₄)₂ (3), [(DMPzA)Co(μ-H₂DPC)Co(TMPzA)]·(ClO₄)₂ (4) [TMPzA = tris(3,5-bimethyl-pyrazolymethyl)amine; bipy = bipyridine; H₂DPC = pyridyl-2,6-bicarboxylate; DMPzA = bis(3,5-bimethyl-pyrazolmethyl)amine]. In order to investigate the effect of the pyridyl ring on the cleavage of the pendant arm in the tripodal ligand, a fifth complex, [(TMPzA)Co(μ-HZPC)Co(TMPzA)·(H₂O)₂]·(ClO₄)₃ (5), has been prepared by using pyrazole-carboxylate (HZPC) instead of pyridyl derivatives, and its crystal structure has been determined. It has been found that the pendant arm in TMPzA ligand has not been removed in complex 5. The results show that the complexes with TMPzA have a strong ability to recognize pyridine compounds in methanol solvent, and they have potential application for molecular devices in the future. The cleavage mechanism has been studied by DFT calculations and ESI-MS spectra.     

Synthesis and Characterization of Aminophosphines,Bis(amino)phosphine Derivatives,and Their Molybdenum(0) Complexes

Functionalized bis(amino)phosphines of the type PhP(NHR)₂ ( 1a–c ) and aminophosphines of the type Ph₂PNHR ( 2a–c ) have been synthesized by treating PhPCl₂ or Ph₂PCl with corresponding primary amines of H₂N-R where R = -CH₂SO₃H, -C₆H₄SO₃H, and benzo-15-crown-5. The molybdenum(0) complex of the aminophosphine ( 3 ) has been obtained by reacting cis-[Mo(CO)₄(bipy)] with aminophosphine ( 2c ). The synthesized aminophosphines, bis(amino)phosphines, and the molybdenum(0) complex have been characterized by IR, ¹H NMR, ³¹P NMR, and MS spectroscopic techniques and by elemental analysis.     

Vapour-liquid equilibrium measurements for binary mixtures of R32, R143a, R134a and R125 with a perfluoropolyether lubricant

In the present work, vapour-liquid equilibria of four binary systems refrigerant-lubricant oil have been investigated, CF₃CHF₂ (R125), CF₃CH₂F (R134a), CF₃CH₃ (R143a) and CH₂F₂ (R32) as refrigerants and a commercial perfluoropolyether (PFPE), Fluorolink D10H, as lubricant. Vapour-liquid equilibrium data, consisting of isothermal measurement of equilibrium pressure at a fixed composition, have been correlated with an extended Flory-Huggins equation and the corresponding parameters have been determined. Good agreement has been found between experimental data and the model predictions.     

Synthesis, characterization, and molecular structure of Ru(II) complex containing 2,5-pyridinedicarboxylic acid

This article presents a combined experimental and computational study of Ru(II) complex containing 2,5-pyridinedicarboxylic acid ligand. The novel complex [Ru(py-2,5-COOH)₂(PPh₃)₂]·3H₂O has been obtained in the reaction of [RuCl₂(PPh₃)₃] with 2,5-pyridinedicarboxylic acid in methanol and has been studied by IR, ¹H, ³¹P NMR, UV–Vis spectroscopy, and X-ray crystallography. The electronic structure of [Ru(py-2,5-COOH)₂(PPh₃)₂] has been calculated with the density functional theory (DFT) method. The spin-allowed electronic transitions of the complex have been calculated with the time-dependent DFT method, and the UV–Vis spectrum has been discussed on this basis and rationalized by determination of ligand field splitting (10Dq) and Racah’s parameters from the experimental spectrum. The luminescence property of the complex has been examined.     

Reactions of [ReX5(NO)]2− with triphenylstibine. Spectroscopic investigations of [ReX2(NO)(SbPh3)3], X-ray structures of [ReCl2(NO)(SbPh3)3] and [ReBr2Cl(SbPh3)3] and DFT calculations for [ReCl2(NO)(SbPh3)3]

The reactions of [NBu₄]₂[ReX₅(NO)] (X = Cl, Br) with triphenylstibine have been examined and three new rhenium complexes – [ReCl₂(NO)(SbPh₃)₃] (1), [ReBr₂(NO)(SbPh₃)₃] (2) and [ReBr₂Cl(SbPh₃)₃] (3) – have been obtained. The last one has been isolated in a low yield during slow recrystallization of the complex 2 from a mixture of chloroform and ethanol. The stibine rhenium nitrosyls have been characterized by IR and UV–vis spectroscopy. The X-ray structures of 1 and 3 have been determined. The geometric parameters of 1 have been examined using the density functional theory (DFT) method.     

Telluroamides and selenoamides: Complexes with chromium,molybdenum, and tungsten pentacarbonyls

Several new telluroamide and selenoamide group 6 metal complexes ( 2a–2f ), C₅H₉NOE-M(CO)₅, where E is Te or Se and M is Cr, Mo, or W, have been successfully synthesized by the reaction between PyM(CO)₅ and 4-(telluroformyl)morpholine ( 1a ) or 4-(selenoformyl)morpholine ( 1b ). The crystal structures of C₅H₉NOSe ( 1b ), C₅H₉NOTe-Cr(CO)₅ ( 2a ), and C₅H₉NOSe-Cr(CO)₅ ( 2d ) have been determined. The changes in the physical properties and structures between free ligands ( 1a , 1b ) and coordinated telluro- or selenocarbonyls (in complexes 2a–2f ) have been investigated. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:57–64, 1998     

Etude thermochimique de carboxylates de cuivresolvates par des amines aromatiques

The carboxylates (formate, acetate, propionate, isobutyrate) of copper(II) solvated by aromatic amines (pyridine; α, β and γ picolines) corresponding to the formula Cu(R?COO)₂(H₂O)_x(Am)_y(x = 0,1 or 2, and γ = 1 or 2) have been prepared. The thermal decomposition has been studied by TG and DTA methods. The standard enthalpies of formation have been determined and a relation has been proposed for the estimation of these values.     

Zinc(II) di(o-hydroxybenzoate) complexes with imidazole and its derivativesSynthesis,thermal characterization and molecular structures

Mixed complexes of the type: Zn(Hsal)₂(Him)₂, Zn(Hsal)₂(Him)₅, Zn(Hsal)₂(4-MeHim)₂ and Zn(Hsal)₂(1,2-diMeim)₂ (where Hsal=OHC₆H₄COO^-, Him=imidazole, 4-MeHim=4-methylimidazole, 1,2-diMeim=1,2-dimethylimidazole) have been synthesized. The application of chemical, thermal and X-ray methods has enabled us to analyze the complexes and their sinters. The gaseous products of pyrolysis of Zn(Hsal)₂(Him)₂ and Zn(Hsal)₂(4-MeHim)₂ have been investigated. Thermal decomposition pathways have been postulated for synthesized complexes. The molecular structures of the Zn(Hsal)₂(Him)₂ and Zn(Hsal)₂(1,2-diMeim)₂ have been solved.     

Studies on metal carboxylates: XI. Reactions of rhenium carbonyl with picolinic acid and of the tungsten(I) complex [W(CO)3(pic)]n with monodentate tertiary phosphines

The reactions of the tungsten(I) complex of picolinic acid [W(CO)₃(pic)]_n with certain monodentate tertiary phosphines affords a convenient route to complexes of the types W(CO)₃(PR₃)₃ and HW(CO)₂(PR₃)₂(pic). The latter hydrido complexes of tungsten(II) have been characterized by infrared and NMR spectroscopy. The reactions of Re₂(CO)₁₀ with picolinic acid have also been investigated and the new series of rhenium(I) derivatives of the types Re(CO)₃(L)(pic), where L = py, 4-Ph-py, PPh₃ or dppe, and Re(CO)₂(L')₂(pic), where L' = PPh₃ or $\text{1}\text{2}$dppe, have been isolated and characterized.     

On the use of common effective core potentials in density functional calculations. I. Test calculations on transition-metal carbonyls

The performance of effective core potentials adjusted at the Hartree-Fock level but applied in density functional calculations has been tested in a set of calculations using various basis sets and/or core potentials. Test molecules have been the first-row transition-metal carbonyls Cr(CO)₆, Fe(CO)₅, and Ni(CO)₄ and the second-row carbonyls Mo(CO)₆, Ru(CO)₅, and Pd(CO)₄. Only “small-core” potentials have been used, and these are able to reproduce molecular structures and bond energies from all-electron calculations. Relativistic effects have been estimated for the second-row carbonyls by using quasi-relativistic core potentials. © 1996 John Wiley & Sons, Inc.     

Homo‐ and Heteronuclear Compounds with a Symmetrical Bis‐hydrazone Ligand: Synthesis,Structural Studies,and Luminescent Properties

Nine new coordination compounds have been synthesized by the reaction of salts of bivalent metal ions (a=Zn^II, b=Cu^II, c=Ni^II, d=Co^II) with the bis(benzoylhydrazone) derivative of 4,6‐diacetylresorcinol (H₄L). Three kinds of complexes have been obtained: homodinuclear compounds [M₂(H₂L)₂]?nH₂O ( 1 a , 1 b , 1 c , and 1 d ), homotetranuclear compounds [M₄(L)₂]?n(solv) ( 2 a and 2 c ), and heterotetranuclear compounds [Zn₂M₂(L)₂]?n(solv) ( 2 ab , 2 ac , and 2 ad ). The structures of the free ligand H₄L?2 DMSO and its complexes [Zn₂(H₂L)₂(DMSO)₂] ( 1 a* ), [Zn₄(L)₂(DMSO)₆] ( 2 a* ), and [Zn_0.45Cu_3.55(L)₂(DMSO)₆]?2 DMSO ( 2 ab* ) were elucidated by single‐crystal X‐ray diffraction. The ligand shows luminescence properties and its fluorimetric behavior towards M^II metals (M=Zn, Cu, Ni and Co) has been studied. Furthermore, the solid‐state luminescence properties of the ligand and compounds have been determined at room temperature. ¹H NMR spectroscopic monitoring of the reaction of H₄L with Zn^II showed the deprotonation sequence of the OH/NH groups upon metal coordination. Heteronuclear reactions have also been monitored by using ESI‐MS and spectrofluorimetric techniques.