Platinum vaporization

No organometallic products from the reaction of palladium or platinum vapors with butadiene have yet been reported. However, the platinum-butadiene condensate is a catalyst for the hydrogenation of butadiene, the product being mainly butane (104). 

Atypical synthesis of naAed NHC-containing complexes has been reported by Cloke and coworkers. As shown in equation (7), the co-condensation of nickel, paUadium, and platinum vapor with the free NHC, TBu, provided two-coordinated homoleptic complexes of Ni(0), Pd(0), and Pt(0) (43). Unfortunately, in addition to the poor yield of the isolated product, this original methodology required a metal vapor synthesis apparatus. 

Platinum vapor, (generated by electron beam evaporation of the molten metal at ca. 2x10 torr), or palladium vapor (by evaporation from a resistively heated hearth at ca.l0 torr)) was allowed to dissolve in a solution of poly(isobutyl-aluminoxane), [ C4H9A10]n ... 

Ruch and Bartell [84], studying the aqueous decylamine-platinum system, combined direct estimates of the adsorption at the platinum-solution interface with contact angle data and the Young equation to determine a solid-vapor interfacial energy change of up to 40 ergs/cm due to decylamine adsorption. Healy (85) discusses an adsorption model for the contact angle in surfactant solutions and these aspects are discussed further in Ref. 86. 

The fixed points in the lTS-90 are given in Tabie 11.39. Platinum resistance thermometers are recommended for use between 14 K and 1235 K (the freezing point of silver), calibrated against the fixed points. Below 14 K either the vapor pressure of helium or a constant-volume gas thermometer is to be used. Above 1235 K radiometry is to be used in conjunction with the Planck radiation law,... 

The noble metal thermocouples, Types B, R, and S, are all platinum or platinum-rhodium thermocouples and hence share many of the same characteristics. Metallic vapor diffusion at high temperatures can readily change the platinum wire calibration, hence platinum wires should only be used inside a nonmetallic sheath such as high-purity alumina. 

Since detailed chemical structure information is not usually required from isotope ratio measurements, it is possible to vaporize samples by simply pyrolyzing them. For this purpose, the sample can be placed on a tungsten, rhenium, or platinum wire and heated strongly in vacuum by passing an electric current through the wire. This is thermal or surface ionization (TI). Alternatively, a small electric furnace can be used when removal of solvent from a dilute solution is desirable before vaporization of residual solute. Again, a wide variety of mass analyzers can be used to measure m/z values of atomic ions and their relative abundances. 

Disulfur decafluoride does not react rapidly with water, mercury, copper, or platinum at ambient temperatures. There is evidence that it slowly decomposes on various surfaces in the presence of water when stored in the vapor state (118). It is decomposed by molten KOH to give a mixture of potassium compounds of sulfur and fluorine. The gas reacts vigorously with many other metals and siUca at red heat (114). At ca 156°C it combines with CI2 or Br2 to form SF Cl or SF Br (119,120). At ca 200°C, S2F2Q is almost completely thermally decomposed into the hexa- and tetrafluoride (121). 

Another important function of metallic coatings is to provide wear resistance. Hard chromium, electroless nickel, composites of nickel and diamond, or diffusion or vapor-phase deposits of sUicon carbide [409-21-2], SiC , SiC tungsten carbide [56780-56-4], WC and boron carbide [12069-32-8], B4C, are examples. Chemical resistance at high temperatures is provided by aUoys of aluminum and platinum [7440-06-4] or other precious metals (10—14). 

Niobium is used as a substrate for platinum in impressed-current cathodic protection anodes because of its high anodic breakdown potential (100 V in seawater), good mechanical properties, good electrical conductivity, and the formation of an adherent passive oxide film when it is anodized. Other uses for niobium metal are in vacuum tubes, high pressure sodium vapor lamps, and in the manufacture of catalysts. 

Pt—Q—Salt, [Pt(NH3)2(HP04)] and [Pt(OH)3] (259,260). Chloride-based baths have been superseded by P-Salt-based baths, which are more stable and relatively easily prepared. Q-Salt baths offer even greater stabiUty and produce hard, bright films of low porosity. Plating under alkaline conditions employs salts of [Pt(OH3)] . These baths are easily regenerated but have low stabiUty. Platinum films have uses in the electronics industry for circuit repair, mask repair, platinum siUcide production, and interconnection fabrication (94). Vapor deposition of volatile platinum compounds such as [Pt(hfacac)2] and... 

The predominant process for manufacture of aniline is the catalytic reduction of nitroben2ene [98-95-3] ixh. hydrogen. The reduction is carried out in the vapor phase (50—55) or Hquid phase (56—60). A fixed-bed reactor is commonly used for the vapor-phase process and the reactor is operated under pressure. A number of catalysts have been cited and include copper, copper on siHca, copper oxide, sulfides of nickel, molybdenum, tungsten, and palladium—vanadium on alumina or Htbium—aluminum spinels. Catalysts cited for the Hquid-phase processes include nickel, copper or cobalt supported on a suitable inert carrier, and palladium or platinum or their mixtures supported on carbon. 

The ITS-90 has its lowest point at 0.65 K and extends upward without specified limit. A number of values assigned to fixed points differ from those of the immediately previous scale, IPTS-68. In addition, the standard platinum resistance thermometer (SPRC) is specified as the interpolation standard from 13.8033 K to 961.78°C, and the interpolation standard above 961.78°C is a radiation thermometer based on Planck s radiation law. Between 0.65 and 13.8033 K interpolation of the scale rehes upon vapor pressure and constant-volume gas thermometry. The standard thermocouple, which in previous scales had a range between the upper end of the SPRT range and the lower end of the radiation thermometer range, has been deleted. 

Dechlorination can be done in the vapor phase with palladium, platinum, copper, or nickel catalysts (23—26) or in the Hquid phase with palladium catalysts (27). The vapor-phase dechlorination of 1,2,4-trichlorobenzene is reported to give good yields of 1,3-dichlorobenzene (24,26). 

Promoters, usually present in smaU amount, which enhance activity or retard degradation for instance, rhenium slows coking of platinum reforming, and KCl retards vaporization of CuCU in oxy-chlorination for vinyl chloride. 

Oxidation catalysts are either metals that chemisorb oxygen readily, such as platinum or silver, or transition metal oxides that are able to give and take oxygen by reason of their having several possible oxidation states. Ethylene oxide is formed with silver, ammonia is oxidized with platinum, and silver or copper in the form of metal screens catalyze the oxidation of methanol to formaldehyde. Cobalt catalysis is used in the following oxidations butane to acetic acid and to butyl-hydroperoxide, cyclohexane to cyclohexylperoxide, acetaldehyde to acetic acid and toluene to benzoic acid. PdCh-CuCb is used for many liquid-phase oxidations and V9O5 combinations for many vapor-phase oxidations. 

Ammonia vapor is mixed with air and converted into nitrogen oxide at an elevated temperature in the presence of a catalyst, which generally contains noble metals such as platinum and rhodium. The optimal gauge temperature is maintained by controlled ammonia and combustion air preheating. The reaction is highly exothermic ... 

Aryl or vinyljluoroformates, when passed in the vapor phase with helium over an alumina or platinum on alumina catalyst eliminate carbon dioxide to give, respect vely,/ZMOroare er or vinyl fluorides [id] (equation 26)... 

The parent system 3 was reported fw the first time as a product obtained in low yield originating from the vapor-phase cyclodehydrogenaticMi of /V,/V -diphenyl-m-phenylenediamine (137) over a platinum-on-magnesium catalyst (Scheme 17) (61JOC1509). 

Co-condensation reaction of the vapors of l,3-di-rcrt-butylimidazol-2-ylidene and nickel, palladium, or platinum gives the coordinatively unsaturated 14-electron sandwiches [L M] (M=Ni, Pd, Pt) of the carbene type (990M3228). Palladium(O) carbene complexes can also be prepared by the direct interaction of l,3-R2-imidazol-2-ylidenes (R=/-Pr, r-Bu, Cy, Mes) (L) with the palladium(O) compound [Pd(P(o-Tol)3)2] (OOJOM(595)186), and the product at the first stage is [(L)PdP(o-Tol)3l, and then in excess free carbene [PdL ]. 

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