Synthesis and molecular structure of platinum(II) complexes with cyclotriphosphazenes containing pyridylalkylamino and pyridylmethoxy groups

The interaction of platinum(II) nitrile complexes with polydentate ligands, pentaphenoxy(2-pyridylmethylamino)cyclotriphosphazene (L¹), pentaphenoxy(3-pyridylmethylamino)cyclotriphosphazene (L²), pentaphenoxy[2-(2-pyridyl)ethylamino]cyclotriphosphazene (L³), and pentaphenoxy(2-pyridylmethoxy)-cyclotriphosphazene (L⁴), was studied. The synthesized complexes were characterized by single-crystal X-ray diffraction, ¹H and ³¹P NMR spectroscopy, IR spectroscopy, FAB mass spectrometry, and other methods. In complexation of phosphazenes L¹-L³ with Pt(II) ions, nitrogen atoms of the pyridine ring and alkylamine fragment participate in the coordination to form chelate rings. In the complex with L⁴, the substituted phosphazene is coordinated via nitrogen atoms of the pyridyl group and cyclotriphosphazene ring to form a sevenmembered ring.     

Toward an Iron(II) Spin-Crossover Grafted Phosphazene Polymer

Two new cyclotriphosphazene ligands with pendant 2,2':6',2″-terpyridine (Terpy) moieties, namely, (pentaphenoxy){4-[2,6-bis(2-pyridyl)]pyridoxy}cyclotriphosphazene (L(1)), (pentaphenoxy){4-[2,6-terpyridin-4-yl]phenoxy}cyclotriphosphazene (L(2)), and their respective polymeric analogues, L(1P) and L(2P), were synthesized. These ligands were used to form iron(II) complexes with an Fe(II)Terpy(2) core. Variable-temperature resonance Raman, UV-visible, and M?ssbauer spectroscopies with magnetic measurements aided by density functional theory calculations were used to understand the physical characteristics of the complexes. By a comparison of measurements, the polymers were shown to behave in the same way as the cyclotriphosphazene analogues. The results showed that spin crossover (SCO) can be induced to start at high temperatures by extending the spacer length of the ligand to that in L(2) and L(2P); this combination provides a route to forming a malleable SCO material.     

Stereoselective C-X and regioselective C-H activation to,and selective C(sp2)-C(sp3) reductive elimination from,platinum compounds with thiophene-derived ligands

Several thiophene-based N^C ligands were synthesized. Strategically, a bromide was incorporated on the 2-position of the thiophene ring. When allowed to react with the platinum tetramethyl dimer, [Pt₂Me₄(µ-SMe₂)₂], platinum(IV) platinacycles were formed by oxidative addition of the C(sp²)-X bond. These platinum(IV) compounds were characterized by NMR and HRMS. The platinum (IV) compounds were subsequently subjected to thermolysis. A series of reactions occurred, including selective C-C reduction elimination and selective C-H oxidative addition, giving mixtures of platinum(II) products with varying degrees of regioselectivity.     

Synthesis and properties of ms- and β-substituted Pt(II) and Pt(IV) tetraphenylporphyrinates

The interaction of 5,10,15,20-tetraphenylporphyrin, 5,10,15,20-tetra-(4-chlorophenyl)porphyrin, 2-bromo-5,10,15,20-tetraphenylporphyrin, and 2,3,12,13-tetrabromo-5,10,15,20-tetraphenylporphyrin with platinum(II) chloride in boiling phenol has been studied. The corresponding platinum(II) porphyrinates have been synthesized; their subsequent treatment with bromine in chloroform resulted in platinum(IV) porphyrinates. The Pt(II) and Pt(IV)(Br)₂ porphyrinates have been identified by elemental analysis, electron absorption, IR, and ¹H NMR spectroscopy.     

The separation of palladium and platinum by ion flotation

Differences in the ion flotation properties of palladium(II) and platinum(IV) chloro complexes in aqueous solutions are used to achieve separations of these metals. The anionic chloro complex PtCl^2-₆ is floated selectively with cationic surfactants of the type, RNR'₃Br, from solutions of PdCl^2-₄ and various concentrations of hydrochloric acid. The palladium(II) does not float from solutions of ? 3.0 M HCl and the platinum(IV) floated from these solutions can be recovered free of palladium. However, the separation is incomplete as much of the platinum(IV) is also unfloated from these solutions. Quantitative separations are obtained by conversion of the palladium(II) to the cationic ammine, Pd(NH₃)₄²⁺ with aqueous ammonia prior to flotation. The anionic chloro complex of platinum(IV) is unaffected by the presence of ammonia and is floated quantitatively with the surfactant n-hexadecyltri-n-propylammonium bromide from 0.01 M ammonia solutions.     

Adsorptive stripping voltammetric measurements of trace amounts of platinum(II) and ruthenium(III) in the presence of 1-(2-pyridylazo)-2-naphthol

An extremely sensitive stripping voltammetric procedure for low level measurements of platinum (II, IV) or ruthenium (III, IV) is reported. The method is based on the interfacial accumulation of the platinum (II) or ruthenium (III)-1-(2-pyridylazo)-2-naphthol complex on the surface of a hanging mercury drop electrode, followed by the reduction of the adsorbed complex during the cathodic scan. The peak potential was found to be –0.8 V vs. Ag/AgCl electrode and the reduction current of the adsorbed complex ions of platinum (II) or ruthenium (III) was measured by differential pulse cathodic stripping voltammetry. The optimum experimental conditions were: 1.5×10^–7 mol/l of 1-(2-pyridylazo)-2-naphthol solution of pH 9.3, preconcentration potential of –0.2 V, accumulation time of 3 min and pulse amplitude of 50 mV with 4 mV s^–1 scan rate in the presence of ethanol-water (30% v/v) — sodium sulphate (0.5 mol/l). Linear response up to 6.4 × 10^–8 and 5.1 × 10^–8 mol/l and a relative standard deviation (at 1.2×10^–8 mol/l) of 2.4 and 1.6% (n=5) for platinum (II) and ruthenium (III) respectively were obtained. The detection limits of platinum and ruthenium were 3.2×10^–10 and 4.1×10^–10 mol/l, respectively. The electronic spectra of the Pt(II) — PAN and Ru(III) — PAN complexes were measured at pH 9.3 and the stoichiometric ratios of the complexes formed were obtained by the molar ratio method. The effects of some interfering ions on the proposed procedure were critically investigated. The method was found suitable for the sub-microdetermination of ruthenium (IV) and platinum (IV) after their reduction to ruthenium (III) and platinum (II) with sulphur dioxide in acid media. The applicability of the method for the analysis of binary mixtures of ruthenium (III) and (IV) or platinum (II) and (IV) has also been carried out successfully. The method is simple, rapid, precise, and promising for the determination of the tested metal ions at micro-molar concentration level.     

Extraction of Palladium(II) and Platinum(IV) from Hydrogen Chloride Solutions with 3,7-Dimethyl-5-thianonane-2,8-dione and Complexation of This Reagent with the Platinum Metals

Extraction of palladium(II) and platinum(IV) from acidic chloride solutions with solutions of 3,7-dimethyl-5-thianonane-2,8-dione in toluene and chloroform and complexation of this reagent with platinum metals in aqueous acetone were studied by ^1Hand ^13C NMR and IR spectroscopy. The possibility of extractive separation of palladium(II) from platinum(IV) and their separation from Cu(II), Ni(II), Co(II), Mn(II) and Fe(III) with solutions of 3,7-dimethyl-5-thianonane-2,8-dione in organic solvents was studied. The apparent concentration constants of extraction of palladium(II) and platinum(VI) with 3,7-dimethyl-5-thianonane-2,8-dione and the corresponding thermodynamic parameters were determined.     

Investigation of trace level binding of PtCl6 and PtCl4 to alfalfa biomass (Medicago sativa) using Zeeman graphite furnace atomic absorption spectrometry

Batch laboratory experiments were performed to investigate the effects of pH, chemical modification, time dependency, and interference studies on the binding of trace concentrations of hexachloroplatinate(IV) and tetrachloroplatinate(II) to alfalfa biomass. The pH profiles were measured between pH 2.0 and 6.0. It was found that the binding of trace concentrations of platinum(IV and II) to alfalfa biomass was dependent on pH with a maximum binding occurring at pH 3.0 and a minimum at pH 6.0. When the alfalfa biomass was chemically modified (esterified), maximum binding occurred at pH 6.0 for both oxidation states of platinum. From the batch time dependency experiments, it was found that binding took at least 20 min to level off for both platinum oxidation states. Batch experiments were performed with various concentrations of calcium, magnesium, and sodium (0.1, 1.0, 10, 100 and 1000 ppm) and it was found that calcium affected the binding of platinum(II and IV) to the alfalfa biomass. It was determined that magnesium and sodium did not interfere appreciably with the binding of platinum in either of the oxidation states studied. Finally, batch experiments were performed with Mg²⁺, Ca²⁺ and Na⁺ in solutions at various concentrations, and it was observed that the binding was affected similarly to that by calcium alone.     

Formation of organometallic complexes of platinum(II) and platinum(IV) in reactions of PtCl62− with alkanes,olefins and aromatics induced by γ-irradiation

γ- Irradiation of solutions of the ion PtCl₆^2? and n-hexane (or alkene) in MeCO₂H affords a π-olefin complex of platinum(II); σ-aryl complexes of platinum(IV) are formed in analogous reactions with aromatic compounds.     

Synthesis and Analysis of the Structure,Diffusion and Cytotoxicity of Heterocyclic Platinum(IV) Complexes

We have developed six dihydroxidoplatinum(IV) compounds with cytotoxic potential. Each derived from active platinum(II) species, these complexes consist of a heterocyclic ligand (H_L) and ancillary ligand (A_L) in the form [Pt(H_L)(A_L)(OH)₂]²⁺, where H_L is a methyl‐functionalised variant of 1,10‐phenanthroline and A_L is the S,S or R,R isomer of 1,2‐diaminocyclohexane. NMR characterisation and X‐ray diffraction studies clearly confirmed the coordination geometry of the octahedral platinum(IV) complexes. The self‐stacking of these complexes was determined using pulsed gradient stimulated echo nuclear magnetic resonance. The self‐association behaviour of square planar platinum(II) complexes is largely dependent on concentration, whereas platinum(IV) complexes do not aggregate under the same conditions, possibly due to the presence of axial ligands. The cytotoxicity of the most active complex, exhibited in several cell lines, has been retained in the platinum(IV) form.     

Synthesis and spectroscopic studies of transition metal dinuclear/ polynuclear complexes with azolo-2,4-pentanedione

Summary Biologically relevant azolo (triazolo and thiazolo) diazonium salts were coupled with 2,4-pentanedione. The resulting substituted 2,4-pentanedione (L₁ and L₂) were condensed with 1,6-diaminohexane in the presence of chloride salts of nickel(II), copper(II), platinum(II), platinum(IV) and palladium(II) or nickel(II) and copper(II) acetates. The resulting dinuclear/polynuclear complexes were characterized by elemental analyses, conductance and magnetic moments, as well as i.r., u.v.-vis., ¹H n.m.r. and e.s.r. spectra.     

Synthesis of N-Methyl-2-Thioimidazole Resin and Its Complex Behavior for Noble Metal Ions

The functional group capacity and the percentage of functional group conversion of crosslinked polystyrene resin bearing N-methyl-2-thioimidazole (MTIR) synthesized under optimum conditions are as high as 4.08 mmol/g resin and 96.0%, respectively. The apparent activation energies of sorption of MTIR for Au(III) and Pt(IV) are 13.1 and 13.4 kJ/mol, respectively. The sorption behavior of MTIR for Au(III), Pt(IV), and Pd(II) obeys the Freundlich and Langmuir isotherms. The sorption capacities of MTIR for Au(III), Pt(IV), and Pd(II) are as high as 4.33, 2.12, and 2.33 mmol/g resin, respectively. Au(III), Pt(IV), and Pd(II) adsorbed on MTIR can be eluted quantitatively by the eluant. The resin can be regenerated easily and reused without an obvious decrease in the sorption capacity for Au(III) and Pd(II). The resin has high sorption selectivity for noble metal ions. Au(III) can be separated quantitatively in the presence of high concentrations of Cu²⁺, Fe³⁺, Ni²⁺, and Mn²⁺. The recovery of platinum from the spent industrial catalysts is 98.6% by MTIR. The preconcentration and separation of palladium and platinum from the anode deposits of electrolysis of crude copper have been investigated. The resin may have potential industrial uses.     

Heat-resistant thermosetting polymers based on a novel tetrakisaminophenoxycyclotriphosphazene

Two heat-resistant thermosetting polymers ( IX and X ) have been developed based on a new cyclotriphosphazene containing tetrakisamine. These polymers were synthesized by the reaction of tetrakisamine ( IV ) with maleic anhydride followed by in situ cyclodehydration and polymerization of the maleimides ( VII and VIII ) at 235–240°C for 1.5 h and 290°C for 0.5 h. The thermogravimetric analyses (TGA) of the developed cyclotriphosphazene containing cyclomatrix polymers showed their thermal stability up to 350°C and char yield of 71% in nitrogen at 800°C and 65% in air at 700°C. The monomer, 2,2,4,4-tetrakis(4′-aminophenoxy) -6,6-diphenylcyclotriphosphazene ( IV ), useful for producing a variety of heat- and fire-resistant polymers, has been synthesized in good yield. Its syntheses involve Friedel-Crafts reaction of hexachlorocyclotriphosphazene ( I ) with benzene followed by the reaction of 2,2,4,4-tetrachloro-6,6-diphenylcyclotriphosphazene ( II ) with potassium 4-nitrophenoxide. The reduction of the obtained 2,2,4,4-tetrakis(4′-nitrophenoxy)-6,6-diphenylcyclotriphosphazene ( III ) with molecular hydrogen in presence of PtO₂ gave the tetrakisamine ( IV ). The structure of the synthesized monomer and intermediates were characterized by FT-IR, ¹H-NMR, ³¹P-NMR, mass spectroscopy, differential scanning calorimetry (DSC), and elemental analysis. These resins are potential candidates for the development of heat- and fire-resistant composites, laminates, and adhesives, useful for space, aerospace, and electronic application. © 1993 John Wiley & Sons, Inc.     

Synthesis,characterization, and cytotoxicity of Pt(IV) complexes containing 1,10-phenanthroline and 2,2′-bipyridine and diaminocyclohexane ligands

Four platinum(IV) complexes containing intercalating ligands [1,10-phenanthroline (phen) and 2,2′-bipyridine (bpy)] and ancillary ligands [(1S,2S)-diaminocyclohexane (SS-DACH) and (1R,2R)-diaminocyclohexane (RR-DACH)] were synthesized and characterized by ¹H nuclear magnetic resonance, electrospray ionization mass spectrometry, X-ray crystal structure analysis, elemental analysis, ultraviolet absorption spectroscopy, circular dichroism spectroscopy, and electrochemical analysis. The reactions between [Pt(phen)(SS-DACH)Cl₂]²⁺ and glutathione and Ac-CPFC-NH₂ were investigated by high-performance liquid chromatography. [Pt(phen)(SS-DACH)Cl₂]²⁺ was reduced to its corresponding Pt(II) complex [Pt(phen)(SS-DACH)]²⁺, while glutathione and Ac-CPFC-NH₂ were oxidized to glutathione-disulfide and a peptide containing an intramolecular disulfide bond, respectively. The cytotoxicities of the Pt(IV) complexes against a human non-small cell lung cancer cell line (A549) and the corresponding cisplatin-resistant cell line (A549cisR) were evaluated. These Pt(IV) complexes showed a higher activity toward A549 and A549cisR than did cisplatin. Also, the cytotoxicities of the Pt(IV) complexes were higher for A549cisR than for A549 cells. Moreover, the cytotoxicities of the (SS-DACH)-liganded platinum complexes were higher than those of the (RR-DACH)-liganded platinum complexes in either A549 or A549cisR cells. Phen-liganded platinum complexes were more cytotoxic than the bpy-liganded platinum complexes. The cytotoxicities of these Pt(IV) complexes had no correlation with reduction potentials.     

Synthesis and Structural Elucidation of N,N ’-Ditosyl-1,11-diaza-4,8,14,18-tetraselena-cycloicosane and its Copper and Platinum Complexes

The reaction of 1,2-diselenacyclopentane with N,O,O-tri-(toluene-p-sulphonate)-diethanolamine afforded a new seleno-azacrown ether, i.e. N,N′-ditosyl-1,11-diaza-4,8,14,18-tetraselena cycloicosane (1), in 19% yield, which was comprehensively characterized by elemental analysis, UV–Vis, ¹H NMR and mass spectroscopy. The reaction of 1 with copper(II) perchlorate (Cu(ClO₄)₂) and platinum(IV) tetrachloride (PtCl₄) gave its corresponding copper (2) and platinum complexes (3), respectively. The crystallographic investigations showed that the disparity of metal ion led not only to the distinct crystal system and space group, i.e. monoclinic system (C2/c) for 2 and triclinic system (P-1) for 3, but also the different coordination modes of copper and platinum ions with 1, i.e. normal coordination mode for 2 and ring-contracted coordination mode for 3. Moreover, the metal ions in the crystals 2 and 3 were found in Cu(I) and Pt(II) forms, respectively, although Cu(II) and Pt(IV) were used at the initial stage of coordination reaction.     

Reaction of platinum complexes with (+)-α-pinene and (+)-limonene. Synthesis, molecular structure, and catalytic activity of dichloro(η4-[p-mentha-1,8{9}-diene])platinum(II)

The transformations of platinum(II) and platinum(IV) complexes with inner-and outer-sphere ligands by the action of (+)-α-pinene and (+)-limonene were studied. Reduction of the metal complex is the main process whose rate increases in the following outer-sphere ligand series: (Me₂SO)₂H⁺ < Et₃NH⁺ < K^? < H⁺. The reaction of K₂PtCl₄ with α-pinene gave cis-terpine monohydrate and dichloro-η⁴-[p-mentha-1,8(9)-diene]platinum(II), and their structure was proved by X-ray analysis. The complex belongs to monoclinic crystal system, the Pt-Cl and Pt-C bonds therein have different lengths, the ClPtCl angle is 85.88°, and the C=C bond plane is orthogonal to the square coordination core. Dichloro-η⁴-[p-mentha-1,8(9)-diene]-platinum(II) was tested as catalyst in the hydrosilylation of acetophenone with diphenylsilane.     

Synthesis and characterization of platinum(II) and (IV) complexes containing hexamethyleneimine ligand: crystal structure of [PtII(hexamethyleneimine)2(cyclobutanedicarboxylato)]·H2O

A series of new platinum(II) and platinum(IV) complexes of the type [Pt^II(HMI)₂X] (where HMI=hexamethyleneimine, X=dichloro, sulfato, 1,1-cyclobutanedicarboxylato [CBDCA], oxalato, methylmalonato, or tatronato) and [Pt^IV(HMI)₂Y₂Cl₂] (where Y=hydroxo, acetato, or chloro) were synthesized and characterized by infrared (IR) spectroscopy, ¹³C and ¹⁹⁵Pt nuclear magnetic resonance (NMR) spectroscopy and elemental analysis. Among the complexes synthesized, [Pt^II(hexamethyleneimine)₂(1,1-cyclobutanedicarboxylato)]·H₂O was examined by single-crystal X-ray diffraction. The slightly distorted square planar coordination environment of the platinum metal includes the amino group of the hexamethyleneimine (HMI) molecule and the oxygen atoms of the carboxylato ligand. The cyclobutanedicarboxylic acid (CBDCA) molecule adopts six-member chelating rings with platinum. Hydrogen bonding plays an important part in holding the crystal lattice together.     

Kinetic Studies of Oxidative Addition Reaction of Arylplatinum(II) Complex Containing 4,4′‐Bipyridine and Calculation of Activation Parameters

New complexes of arylplatinum(II) and arylplatinum(IV) containing a bridging ligand, 4,4′‐bipyridine, were synthesized by the reaction of starting material of platinum(II) including para‐tolyl groups,[(p‐MeC₆H₄)₂Pt(SMe₂)₂], with the 4,4′‐bipyridine ligand in 1:1 molar stoichiometry. In the synthesized complexes, the ligand was bonded to the platinum center through the nitrogen donor atoms. To investigate the kinetic reaction of the platinum(II) complex with iodomethane (CH₃‐I) as a reagent, the oxidative addition reaction of this reagent with Pt(II) was performed in dichloromethane and a Pt(IV) complex with the octahedral geometry was formed. The synthesized complexes have been characterized by different spectroscopic methods such as FT‐IR, ¹H NMR, UV–vis, and elemental analysis. Moreover, the conductivity measurements showed nonelectrolyte characteristics for these complexes. The obtained data showed that the complexes have 1:1 metal‐to‐ligand molar ratio. Also, the oxidative addition reaction of CH₃I with the arylplatinum(II) complex at different temperatures was used for obtaining kinetic parameters such as rate constants, activation energy, entropy, and enthalpy of activation using the Microsoft Excel solver. From the acquired data, an S_N2 mechanism was suggested for the oxidative addition reaction.     

NMR (195Pt and 13C) contribution to the study of some Pt(II), Pt(IV) and mixed-valence thioamido complexes

The ¹⁹⁵Pt and ¹³C chemical shifts (δ_Pt and δ_c) are reported for platinum(II), platinum(IV) and class II mixed-valence complexes, with general formula [PtL₄]X₂, cis- and trans-PtL₂X₂, PtL₂X₄ and Pt₂L₄X₆ (where L may be thiourea, 2-imidazolidine-thione, tetrahydro 2-pyrimidinethione, thiocaprolactam, pyridine-2-thione and tetramethylthiourea, and X may be Cl or Br). The ¹⁹⁵Pt chemical shifts can be understood in view of ¹³C data in terms of variations of electronegativities and σ-donor abilities of ligands attached to platinum.     

Construction and structural analysis of mono- and heterobimetallic bis(titanate) molecular cages

To explore the utility of bis(dihydroxynaphthalene) ligands for the construction of supramolecular structures, we demonstrated the preparation of cage-shaped complexes by combining these ligands with hexacoordinate titanium(IV). The reaction of biphenylenebis(dihydroxynaphthalene) with TiO(acac)₂ proceeded in the presence of N-methylmorpholine in DMF and an M₂L₃-type cage was obtained by self-organization. As an extension of this work, the preparation of heterobimetallic molecular cages was examined by using combinations of titanium(IV), palladium(II) or platinum(II), and pyridyldihydroxynaphthalenes. Ti(IV)/Pd(II) cages were prepared in one pot by treatment of the pyridyldihydroxynaphthalene ligands with TiO(acac)₂ followed by PdCl₂(MeCN)₂. In the preparation of Ti(IV)/Pt(II) cages, platinum(II)-bridged bis(dihydroxynaphthalene) ligands were isolated in advance from the reaction of pyridyldihydroxynaphthalene ligand precursors with K₂PtCl₄, which were then deprotected and reacted with TiO(acac)₂ in the same conditions as those for biphenylenebis(dihydroxynaphthalene). The precise structures of the Ti(IV)/Pd(II) and Ti(IV)/Pt(II) heterobimetallic cages were fully elucidated by X-ray crystallographic analysis.