Diastereoselective assembling of 21-C-alkylated nickel(II) complexes of inverted porphyrin on a platinum(II) template

Reaction of 21-C-methyl and 21-C-benzyl nickel(II) complexes of inverted meso-tetratolylporphyrin with platinum(II) dichloride or its bis(benzonitrile) complex yields a chloroplatinum(II) species containing two nickel(II) carbaporphyrinoids in a cis arrangement. One of the carbaporphyrinoids coordinates to the platinum ion with the external nitrogen while the other is bound with the external nitrogen and one ortho-carbon of the adjacent meso-aryl ring. The reaction is highly chemoselective. (1)H and (13)C NMR experiments in solution show the diastereoselectivity of the reaction. Single-crystal X-ray data confirm the presence of the diastereomer with opposite configurations of the Ni(II)-coordinated carbons in the subunits of the dimer. Cyclovoltammetric measurements reveal an anodic shift of the nickel(II) oxidation potentials of dimers with respect to those of the parent monomers and two different reduction couples. Reaction of unsubstituted inverted porphyrin with Pt(PhCN)(2)Cl(2) in chlorobenzene yields a monomeric platinum(II) complex of inverted porphyrin. This complex displays a markedly upfield (195)Pt NMR shift compared to tetraphenylporphyrinatoplatinum(II). Under strongly basic conditions deprotonation of the external nitrogen of inverted porphyrin and both electrochemical and chemical oxidation of platinum(II) center are observed.     

Liquid-liquid extraction of platinum(II) with cyclic tetrathioethers

The liquid-liquid extraction of platinum(II) with 12-, 14- and 16-membered cyclic tetrathioethers from chloride solution was studied. Bromocresol Green ion as a counter anion and 1,2-dichloroethane as an extraction solvent were used. The effect of thiourea on the extraction rate of platinum(II) was examined. Platinum(II) was hardly extracted with macrocyclic tetrathioethers in the absence of thiourea because of the slow extraction rate. The extraction rate of platinum(II) was considerably enhanced by the addition of thiourea. The extraction rate of platinum(II) with 16-membered cyclic tetrathioether was faster than that with 12- and 14-membered ones. Platinum(II) was quantitatively extracted with 16-membered cyclic tetrathioether into 1,2-dichloroethane within 5 h in the presence of thiourea.     

The effect of platinum(IV) on the coulometric generation of tin(II)

The current efficiency of tin(II) generation has been measured for various electrolytes and electrodes. The best results (>99.9%) were obtained with the paraffin-impregnated graphite electrode in 2M CaCl(2) + 0.2M HCl + 0.2M SnCl(4). In titrations of platinum(IV) with electrogenerated tin(II) in an electrolyte containing chloride or bromide it was found that the presence of platinum(II) or (IV) interferes in the cathodic generation of tin(II). The platinum is reduced to the elemental state at the electrode and causes simultaneous generation of hydrogen which decreases the current efficiency. This effect is more pronounced in chloride media.     

Electrochemical behaviour ofcis-dichloro(arylisocyanide)(tertiaryphosphine) platinum (II) and palladium(II) complexes in an aprotic solvent

Summary The electrochemical behaviour of neutral platinum(II) and palladium(II) isocyanide complexes has been investigated in an aprotic medium at platinum and mercury electrodes. Platinum(II) derivatives are reduced to platinum(0) species, Palladium(II) compounds give rise to palladium(0) species at room temperature, while at 0° it is possible to obtain palladium(I) compounds.     

Simultaneous determination of platinum(II) and platinum(IV) by controlled-reagent coulometry

Both platinum(II) and the total amount of platinum were determined in the 5-μmole range with a precision of 0.3%. First, platinum(II) was determined dy oxidation with electrogenerated bromine,the equivalent quantity of electricity being measured. After reduction to platinum(II) with electrogenarated tin(II), the total amount of platinum was determined by a second oxidation with electrogenerated bromine.The reduction with tin(II) was too slow for manual control, and an electronic coulometric titrator was used.The construction of the tritator is described. The underlying coulometric principle, called controlled-reagent coulometry, and its adventages are discussed. A number of other substances were also tested.     

Ion exchange equilibria in simultaneous extraction of platinum(II,IV) and rhodium(III) from hydrochloric solutions

Regularities of sorption extraction of platinum(II, IV) and rhodium(III) by anion exchangers of various physical and chemical structure in the presence of hydrochloric media were studied. It is established that AM-2B, Purolite A 500, and Purolite S 985 ionites adsorb complex anions of platinum metals employing mixed mechanism. A high affinity of the studied anionites for the studied complex anions of platinum and rhodium is established.     

Spectrophotometric determination of osmium(IV), iridium(IV) and platinum(iv) and separation and determination of palladium(II) and ruthenium(III) in the presence of other platinum metals, with oximidobenzotetronic acid as reagent

Oximidobenzotetronic acid is suggested as a reagent for the spectrophotometric determination of osmium(IV), iridium(III), iridium(IV), platinum(IV) and for separation and determination of palladium(II) and ruthenium(III) in the presence of other platinum metals. Iridium(III) and (IV) can be estimated when present together.     

Simultaneous determination of platinum(II) and palladium(II) by reversed phase high-performance liquid chromatography with spectrophotometric detection after collection on and elution from resin coated with dimethylglyoxal bis(4-phenyl-3-thisomicarbazone)

Amberlite XAD-7 resin coated with dimethylglyoxal bis(4-phenyl-3-thiosemicarbazone) (DMBS) was prepared and applied to the preconcentration of platinum(II) and palladium(II) from aqueous solution. Platinum(II) and palladium(II) were collected quantitatively on resin coated with the reagent (DMBS-XAD-7) from acidic solution in the presence of iodide ion by a bach method. The metal ions were then easily eluted from DMBS-XAD-7 as their DMBS chelates with a small volume of N,N-dimethylformamide. This collection and elution method was applied to the simultaneous determination of platinum(II) and palladium(II) by reversed-phase high-performance liquid chromatography with spectrophotometric detection using an ODS column and acetone-water as the mobile phase. The proposed method was applied to the determination of the metals in commercially available samples.     

Interaction of Dinitrogentrioxide with Platinum(0) and Palladium(0) Complexes

Dinitrogentrioxide reacts with tetrakis(triphenylphosphine) platinum and palladium under nitrogen to give dinitrobis(triphenylphosphine) platinum(II) and palladium(II) complexes, respectively. In the presence of oxygen these reactions afford the formation of nitro-nitrato complexes of platinum(II) and palladium(II). The products are characterized by the elemental analyses, i.r. spectra, conductivity and magnetic measurements.     

Structures of platinum(II) complexes of 2-aminomethylaziridine and S-2-aminomethylazetidine and correlation of anticancer activities of (2-aminomethylazacycloalkane)platinum(II) complexes with the geometry of the chelate rings formed with platinum(II)

The spectroscopic properties of platinum(II) complexes with 2-aminomethyl-derivatives of small-membered 1-aza-cycloalkane, i.e., =2-aminomethylaziridine=azida and S-2-aminomethylazetidine=S-azeda, and the crystal structures of their dichloro complexes demonstrate that the conformation of the fused three- (azida) or four- (S-azeda) and five-membered chelate ring formed by the coordination of S-azida and S-azeda to platinum(II) has an S(N) absolute configuration at the secondary amine site and that the two alkyl groups extend axially from the five-membered chelate ring. The chelate ring of the azida is more planar than the S-azeda or other 2-aminomethyl-1-azacycloalkanes. The anticancer activity reported for azeda and 2-aminomethylpyrrolidine appears to be related to their coordination structure, namely the presence of cis-fused successive rings.     

Catalytic amperometric and catalytic constant-current potentiometric titrations of silver(I), palladium(II) and mercury(II)

Amperometry and constant-current potentiometry were used to follow the course of catalytic titrations of silver(I), palladium(II), and mercury(II) with potassium iodide. The Ce(IV)As(III) and Ce(IV)Sb(III) systems in the presence of sulphuric acid were used as indicator reactions. The possibilities of application of platinum, palladium, gold, graphite, and glassy-carbon indicator electrodes were investigated. Graphite appeared to be somewhat more advantageous than the other electrode materials. The effect of concentration of the components of the indicator reactions, the presence of organic solvents and acids on the shape of the catalytic titration curves was studied. Amounts of 30-3000 mug of silver(I) nitrate, 90-900 mug of palladium(II) chloride, 130-1300 mug of mercury(II) chloride, and 150-1500 mug of mercury(II) nitrate were determined with a relative standard deviation less than 1.0%. The results obtained were in good agreement with those of comparable methods. The catalytic titration method developed was applied to determination of mercury in Unguentum Hydrargyri.     

Rearrangement of a (dithiolato)platinum(II) complex formed by reaction of cyclic disulfide 7,8-dithiabicyclo[4.2.1]nona-2,4-diene with a platinum(0) complex: oxidation of the rearranged (dithiolato)platinum(II) complex

Reaction of the title bicyclic disulfide 16 with [(Ph3P)2Pt(eta2-C2H4)] (2) yielded the corresponding (dithiolato)platinum(II) complex 17 by oxidative addition. The initial product 17 isomerized at room temperature in a [1,5]-sulfur rearrangement to give another (dithiolato)platinum(II) complex 18 in high isolated yield. Oxidation reactions of 18 with dimethyldioxirane (DMD) provided (sulfenato-thiolato)platinum(II) 23, (sulfinato-thiolato)platinum(II) 24, (sulfenato-sulfinato)platinum(II) 25, and (disulfinato)platinum(II) 26 complexes, the structures of which were elucidated by NMR spectroscopy and X-ray crystallography. The oxidation process took place regioselectively in the first step and chemoselectively in the second. The selectivities are discussed.     

Hydrosilylation of low-molecular siloxanes in the presence of photactivated alkene and sulfoxide platinum(II) complexes

Hydrosilylation of tetramethyldivinyldisiloxane with pentamethyl-and tetramethyldisiloxane in the presence of photoactivated alkene and sulfoxide platinum(II) complexes was studied. The most active photoactivated catalysts are bis-sulfoxide platinum complexes; an additional photosensitive center, the oxalate ligand, enhances the effect of photoirradiation.     

Synthesis of achiral NCN pincer Pt(II) and Pd(II) complexes and catalytic application in the Suzuki-Miyaura reaction

A series of platinum and palladium pincer complexes supported by achiral 1,3-bis(2′-imidazolinyl)benzene-based NCN ligands have been prepared via direct C2 metalation. Meanwhile, ligand precursor 3b and Pt(II) complex 4b were characterized by crystallographic studies, which reveals that the platinum atom in 4b adopts a distorted-square-planar geometry. The Pd(II) pincer complexes 5b was found to be an efficient catalyst for Suzuki cross-coupling reaction of aryl bromides and phenylboronic acid under air. In the presence of 0.5?mol% of Pd(II) 5b in DMF/K₃PO₄·3H₂O for 8?h, the corresponding biaryl products could be obtained in 24–99% yields.     

Spectrophotometric determination of noble metals with tin(II) in bromide solutions

In presence of tin(II) bromide, noble metals give coloured products which are suitable for spcctrophotometric determinations. The colours are red (platinum), yellow-orange (rhodium), yellow-brown (palladium), yellow (iridium) and violet (gold) They are extracted, except for gold, with isoamyl alcohol Platinum, rhodium and palladium can be separated from irdium, and rhodium and platinum from palladium. Rhodium and platinum can be determined simultaneously.     

Palladium(II) and platinum(II) bind strongly to an engineered blue copper protein

Studies of palladium(II) and platinum(II) binding to well-characterized proteins contribute to understanding the influence of these metals in the environment and body. The well-characterized apoprotein of azurin has a soft-metal binding site that may be exposed to solvent by mutation of a coordinating His-117 residue to glycine (H117G). Palladium(II) and platinum(II) form strong 1:1 adducts with the apo form of H117G azurin. A combination of UV-vis, circular dichroism, and inductively coupled plasma mass spectrometry techniques suggests that the metal binds specifically at His-46 and Cys-112 of the protein.     

Photophysical and electrochemical properties of platinum(II) complexes bearing a chromophore-acceptor dyad and their photocatalytic hydrogen evolution

A series of platinum(II) complexes bearing a chromophore-acceptor dyad obtained by reacting 4-(p-bromomethylphenyl)-6-phenyl-2,2'-bipyridine or 4'-(p-bromomethylphenyl)-2,2':6',2'-terpyridine with pyridine, 4-phenylpyridine, 4,4'-bipyridine, 1-methyl-4-(pyridin-4'-yl)pyridinium hexafluorophosphate respectively, were synthesized. Their photophysical properties, emission quenching studies by Pt nanoparticles and methyl viologen, electrochemical properties and photoinduced electron-transfer reactions in a photocatalytic hydrogen-generating system containing triethanolamine and colloidal Pt without an extra electron relay, were investigated. A comparison of the rates of hydrogen production for the two photocatalytic systems, one containing a metal-organic dyad and the other comprising a 1:1 mixture of the parental platinum(II) complexes and the corresponding electron relay, showed that intramolecular electron transfer improves the photocatalytic efficiency. Compared with cyclometalated platinum(II) complexes, the related platinum(II) terpyridyl complexes exhibited poor performance for photocatalytic hydrogen evolution. An investigation into the amount of hydrogen generated by three platinum(II) complexes containing cyclometalated ligands with methyl groups located on different phenyl rings revealed that the efficiency of hydrogen evolution was affected by a subtle change of functional group on ligand, and the hydrogen-generating efficiency in the presence or absence of methyl viologen is comparable, indicating electron transfer from the excited [Pt(C^N^N)] chromophore to colloidal Pt. (1)H NMR spectroscopy of the metal-organic dyads in an aqueous solution in the presence of excess triethanolamine revealed that the dyad with a viologen unit was unstable, and a chemical reaction in the compound occurred prior to irradiation by visible light under basic conditions.     

Water-tolerant enantioselective carbonyl-ene reactions with palladium(II) and platinum(II) Lewis acid catalysts bearing BINAP

Palladium(II) and platinum(II) Lewis acid catalysts bearing BINAP have been proved to be water-tolerant in enantioselective carbonyl-ene reactions, thus arylglyoxal monohydrate could be used directly as substrate achieving good to excellent enantioselectivities as high as 95.4% e.e.. The enantioselective carbonyl-ene reactions using phenylglyoxal monohydrate as substrate with four alkenes including methylenecyclohexane, 2,3-dimethyl-1-butene, 2,4,4-trimethyl-1-pentene and alpha-methylstyrene, were investigated demonstrating comparable or even higher yields and enantioselectivities in comparison with the corresponding carbonyl-ene reactions using dry phenylglyoxal as substrate for both palladium(II)-BINAP catalyst and platinum(II)-BINAP catalyst. The palladium(II) and platinum(II)-BINAP catalyzed enantioselective carbonyl-ene reactions between 4-methylphenylglyoxal monohydrate and the four alkenes were also investigated affording enantioselectivities between 76.2% and 91.8% e.e.. A mechanism involving the coordination of arylglyoxal and 2,2-dihydroxy-1-phenylethanone with chiral catalyst was proposed to interpret the enantioselective carbonyl-ene reactions using arylglyoxal monohydrate as substrate.     

Comparative studies of photophysical and photochemical properties of solketal substituted platinum(II) and zinc(II) phthalocyanine sets

A complete set of platinum(II) solketal substituted phthalocyanines has been synthesized and characterized. To evaluate their potential as Type II photosensitizers for photodynamic therapy, comparative studies of their photophysical and photochemical properties with analogous zinc(II) series have been achieved: electronic absorption, fluorescence quantum yields, lifetimes, and fluorescence quenching by benzoquinone, as well as singlet oxygen generation and photodegradation. It appears that platinum(II) phthalocyanines are worth being used as Type II photosensitizers, as they exhibit good singlet oxygen generation and appropriate photodegradation.     

Novel platinum(II) ammine hydroxamate and hydroximate complexes and the platinum-assisted hydrolysis of hydroxamic acids

The 2-pyridinecarboxylate (2-pyca) platinum(IV) complex [2-pycaH2][PtCl4(2-pyca)].H2O, 1, has been synthesised from K2[PtCl4] following the hydrolysis of 2-pyridinehydroxamic acid (2-pyhaH) in the presence of H2O2, and directly from K2[PtCl6] and picolinic acid. Structural characterisation of 1 reveals octahedral geometry about platinum(IV) consisting of a (N,O)-bidentate pyridinecarboxylate ligand and four chloride ligands. A mechanism for the hydrolysis of 2-pyridinehydroxamic acid to 2-pyridinecarboxylic acid is proposed. Two novel coordination modes of hydroxamic acids to platinum(II) are also reported. The dinuclear platinum ammine hydroximato complex, [{cis-Pt(NH3)2}2(mu-2-pyhaH(-1))](ClO4)2.H2O, 3, has been synthesised where the two platinum(II) centres are bridged via(O,O) and (N,N) coordination. The latter coordination mode is via the hydroximate nitrogen and the pyridine nitrogen. The corresponding mononuclear platinum(II) pyridinehydroxamate complex, [cis-Pt(NH3)2(2-pyha)]ClO4, 4, has been synthesised. Spectroscopic studies indicate that the coordination mode is through the pyridine nitrogen and hydroxamate oxygen atoms (N,O).