Formation of methyl platinum complex in the reaction of methane with chloroplatinic acid

The¹HNMR method and chemical analysis indicate that a complex of Pt(IV) containing a CH₃–Pt fragment is formed in the reaction of H₂PtCl₆+H₂PtCl₄ with methane at 120 °C in aqueous CF₃CO₂H. The complex was isolated from the solution as an adduct of Ph₃P.

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, H₂PtCl₆ H₂PtCl₄ CF₃COOH 120°C (IV), Pt–CH₃. Ph₃P , .

     

N-Thiophosphoryl imines: convenient substrates in the aza-Henry reaction

In the presence of 1,1,3,3-tetramethylguanidine (TMG), N-diethoxythiophosphorylimines 1 and N-diphenylthiophosphinoylimines 2 exhibited good reactivity in the aza-Henry reaction. The corresponding products were obtained in excellent chemical yields under mild conditions. Moreover, the asymmetric version of the N-thiophosphoryl imine 1-based aza-Henry reaction was also realized with ee values up to 87% by employing Takemoto’s thiourea as the catalyst.     

The reaction of carbon monoxide with platinum ylids

The platinum(II) ylids [X₂Pt{CH(py)CH₂CH₃}(py)] (X = Cl, Br; PY = pyridine) react with carbon monoxide to give the platinum carbonyls [CO(X₂)Pt{CH(py)CH₂CH₂CH₃}] which lose CO on heating or in solution. The platinum(IV) ylids [Cl₄Pt{CH(py)CH₂CH₃}(py)] and[Cl₂I(CH₃)Pt{CH(py)CH₂CH₃}(py)] also react with CO to give Pt(CO)-ylid compounds.     

Pt/Pd/C catalysts with ultra low platinum content for oxygen reduction reaction

The activity of Pt/Pd/C ETEK catalysts of the core-shell type with an ultralow content of platinum (0.5–15 μg cm^?2) based on a commercial palladium catalyst is shown to exceed the activity of commercial Pt/C ETEK catalysts in the oxygen reduction reaction. The activity sharply increases with the decrease in the platinum content down to values corresponding to monolayer and submonolayer of platinum on palladium. This dependence wasn’t observed for the same amounts of platinum deposited on the carbon support Vulcan XC-72. This makes it possible to conclude that the most probable factor responsible for the high catalytic activity of Pt/Pd/C ETEK is the effect of palladium on the electronic properties of platinum rather than the effect of structural modification of the platinum deposit induced by the decrease in the platinum amount deposited on a foreign metal or a carbon support.     

Formation of bicyclic compounds in the reaction of 3-methyl-2,3-epoxysulfolane with thiocyanic acid

In the presence of an equivalent amount of sulfuric acid 3-methyl-2,3-epoxysulfolane reacts with sodium thiocyanate with primary opening of the oxy ring at the C₍₃₎-O bond to give, as the principal product, 5-methyl-3-oxo-2-oxa-4,8-dithiabicyclo[3.3.0]octane 8,8-dioxide.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 331–335, March, 1985.     

Formation of Pt-S-Mn groups in platinum triphenylphosphine complexes with cymanthrenylthiolate ligands

Stepwise decarbonylation of the platinum complex with cymanthrenylthiolate ligands cis-(Ph₃P)₂Pt[(SC₅H₄)Mn(CO)₃]₂ (1) affords the cis-(Ph₃P)₂Pt[(SC₅H₄)Mn(CO)₃]-[(SC₅H₄)Mn(CO)₂] (2) and cis-(Ph₃P)₂Pt[(SC₅H₄)Mn(CO)₂]₂ (3) complexes. The replacement of one carbonyl group at the manganese atom with the lone electron pair of sulfur is accompanied by the formation of a new Mn-S bond giving rise to an unusual norbornane-type core. Complexes 1–3 were characterized by elemental analysis and IR spectroscopy. The structures of complexes 1–3 were established by single-crystal X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1508–1512, July, 2005.     

Formation of anionic σ-aryl complexes of platinum (IV) in the reaction of H2PtCl6 with aromatic compounds. The crystal and molecular structures of platinum (IV) complexes of naphthalene and ortho-nitrotoluene

The crystal and molecular structures of anionic platinum(IV) complexes of naphthalene (I) and ortho-nitrotoluene (II) have been determined by X-ray diffraction. The structures of both complexes are similar. The platinum atom is octahedrally coordinated with four chlorine atoms occupying the equatorial positions and σ-bonded aryl and neutral ammonia ligands situated in the axial positions.     

Formation of 3-ethylpyrroles in the synthesis of 3H-pyrroles from isopropyl ketoximes in the trofimov reaction

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, p. 2659, November, 1990.     

A structural model for barium platinum oxide,Ba3Pt2O7

A single crystal study of Ba₃Pt₂O₇ shows that the structure tolerates a variable composition which can be written Ba₃Pt_2+xO_7+2x. The crystal studied has a hexagonal cell of dimensions a = 10.108 ± 0.006 Å and c = 8.638 ± 0.009 Å, and a probable space group $\text{P}\text{6}\text{2c, Z = 4}$. The density determined by water displacement is 7.99 g/cm³; the theoretical density for Ba₃Pt₂O₇ is 7.94 g/cm³. The structure was determined from the set of 401 observed independent reflections obtained from 5189 reflections measured by automated counter methods. Refinement on F was carried to a conventional R of 8.0%. The structure has barium-oxygen layers with an essentially four-layer stacking sequence of the double hexagonal (ABAB) type. Platinum is found mainly in face-sharing octahedra, but is also distributed over some sites in which the coordination is nearly square planar and other sites in which the coordination is trigonal prismatic with three PtO bond lengths of 2.00 Å and three long PtO distances of 2.65 Å. The platinum with planar coordination is 0.08 Å from the plane of the four oxygen atoms.     

Synthesis of platinum nanoparticles by reaction of filamentous cyanobacteria with platinum(IV)-chloride complex

Interaction of cyanobacteria (Plectonema boryanum UTEX 485) with aqueous platinum(IV)-chloride (PtCl(4) degrees ) has been investigated at 25-100 degrees C for up to 28 days, and 180 degrees C for 1 day. The addition of PtCl(4) degrees to the cyanobacteria culture initially promoted the precipitation of Pt(II)-organic material as amorphous spherical nanoparticles (< or =0.3 microm) in solutions and dispersed nanoparticles within bacterial cells. The spherical Pt(II)-organic nanoparticles were connected into long beadlike chains by a continuous coating of organic material derived from the cyanobacterial cells, and aged to nanoparticles of crystalline platinum metal with increase in temperature and reaction time. The stepwise reduction for the formation of platinum nanoparticles in the presence of cyanobacteria was deduced to be Pt(IV) [PtCl(4) degrees ] --> Pt(II) [Pt(II)-organics] --> Pt(0). Spherical platinum-bearing nanoparticles were not present in abiotic PtCl(4) degrees experiments conducted under similar conditions and duration.     

Formation of ammonium salts of 2-amino-3-formylbutanesulfinic acids in the reaction of 3-methyl-2,3-epoxysulfolane with amines

The reaction of 3-methyl-2,3-epoxysulfolane with amines proceeds with opening of not only the epoxide ring but also opening of the sulfolane ring to give the corresponding salts of 2-amino-3-formylbutanesulfinic acids.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1481–1483, November, 1985.     

Unique activity of platinum adislands in the CO electrooxidation reaction

The development of electrocatalytic materials of enhanced activity and efficiency through careful manipulation, at the atomic scale, of the catalyst surface structure has long been a goal of electrochemists. To accomplish this ambitious objective, it would be necessary both to obtain a thorough understanding of the relationship between the atomic-level surface structure and the catalytic properties and to develop techniques to synthesize and stabilize desired active sites. In this contribution, we present a combined experimental and theoretical study in which we demonstrate how this approach can be used to develop novel, platinum-based electrocatalysts for the CO electrooxidation reaction in CO(g)-saturated solution; the catalysts show activities superior to any pure-metal catalysts previously known. We use a broad spectrum of electrochemical surface science techniques to synthesize and rigorously characterize the catalysts, which are composed of adisland-covered platinum surfaces, and we show that highly undercoordinated atoms on the adislands themselves are responsible for the remarkable activity of these materials.     

Formation of 3-Methylfuran from the gas-phase reaction of OH radicals with isoprene and the rate constant for its reaction with the OH radical

3-Methylfuran has been identified as a product of the gas-phase reaction of the OH radical with isoprene, and under simulated atmospheric conditions a formation yield of 0.044 ± 0.006 was determined. In an analogous manner, the OH radical reaction with 1,3-butadiene formed furan with a yield of 0.039 ± 0.011. Using a relative rate method, a rate constant for the reaction of the OH radical with 3-methylfuran of 9.35 × 10^?11 cm³ molecule^?1 s^?1 (with an estimated overall uncertainty of ±20%) at 296 ± 2 K was also determined. These data show that 3-methylfuran is a reactive compound which will be present in the troposphere at concentrations ?5% of those of its isoprene precursor.     

Chimeric platinum-polyamines and DNA binding. Kinetics of DNA interstrand cross-link formation by dinuclear platinum complexes with polyamine linkers

The first observation of a polyamine-DNA interaction using 2D [(1)H, (15)N] HSQC NMR spectroscopy allows study of the role of the linker in polynuclear platinum-DNA interactions and a novel "anchoring" of the polyamine by Pt-DNA bond formation allows examination of the details of conformational B → Z transitions induced by the polyamine. The kinetics and mechanism of the stepwise formation of 5'-5' 1,4-GG interstrand cross-links (IXLs) by fully (15)N-labeled [{trans-PtCl((15)NH(3))(2)}(2){μ-((15)NH(2)(CH(2))(6)(15)NH(2)(CH(2))(6)(15)NH(2))}](3+) (1,1/t,t-6,6, 1) and [{trans-PtCl((15)NH(3))(2)}(2){μ-((15)NH(2)(CH(2))(6)(15)NH(2)(CH(2))(2)(15)NH(2)(CH(2))(6)(15)NH(2))}](4+) (1,1/t,t-6,2,6, 1') with the self-complementary oligonucleotide 5'-{d(ATATGTACATAT)(2)} (duplex I) are compared to the analogous reaction with 1,0,1/t,t,t (BBR3464) under identical conditions (pH 5.4, 298 K). Initial electrostatic interactions with the DNA are delocalized and followed by aquation to form the monoaqua monochloro species. The rate constant for monofunctional adduct formation, k(MF), for 1 (0.87 M(-1) s(-1)) is 3.5 fold higher than for 1,0,1/t,t,t (0.25 M(-1) s(-1); the value could not be calculated for 1' due to peak overlap). The evidence suggests that several conformers of the bifunctional adduct form, whereas for 1,0,1/t,t,t only two discrete conformers were observed. The combined effect of the conformers observed for 1 and 1' may play a crucial role in the increased potency of these novel complexes compared to 1,0,1/t,t,t. Treated as a single final product, the rate of formation of the 5'-5' 1,4-GG IXL, k(CH), for 1 (k(CH) = 4.37 × 10(-5) s(-1)) is similar to that of 1,0,1/t,t,t, whereas the value for 1' is marginally higher (k(CH) = 5.4 × 10(-5) s(-1)).     

Formation of 3-phenylhydrazono-3-aroylpropionamides from the reaction of 5-aroyl-3(2H)-isothiazolones with phenylhydrazine

Reaction of 2-substituted-5-aroyl-3(2H)-isothiazolones 1 with phenylhydrazine in refluxing ethanol was found to give sulfur-free products, which were characterized as 3-phenylhydrazono-3-aroyl-N-substituted-pro-pionamides 4. Acid hydrolysis of the 3-benzoyl compounds 4 was shown to yield 1-phenyl-3-benzoyl-2-pyrazolin-5-one ( 7 ), whose structure was confirmed by an independent synthesis starting with the chloride of 1-phenyl-5-methoxypyrazole-3-carboxylic acid ( 10 ).