Nickel and platinum

Nickel and Platinum.—Cycloaddition reactions of various alkynes with CpgNi have afforded new derivatives of the known structural class CpNi( x, r-norborna-dien-7-yl) the product of addition of H02CC CC02(menthyl) has been resolved into optically-active forms. The er-methyl complexes CpNi[P(OR)3]Me have been obtained from reactions of CpNi[P(OR)3]Cl with MeLi. Several new platinum complexes of the type CpPt(R)2X (R = alkyl X = alkyl or acyl) have been synthesized.  

Copper.—Metal-ring cleavage reactions of CpCuL (L = PBus or SMe2) with acyl and alkyl halides have been reported.  

Yamamoto, T. Mise, and H. Yamazaki, Bull. Chem. Soc. Japan, 1978, 51, 2743. 

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Copper or glass-lined equipment for carbonyl in the presence of carbon monoxide Most common metals for dry gas. For moist gas use 18 8 stainless steel, PTFE Any common metal Most common metals for dry gas. For moist gas use 18 8 stainless steel Nickel and Monel are preferred. Steel, copper and glass are acceptable at ordinary temperatures Steel for dry gas otherwise use 18 8 stainless steel Nickel, Monel and Inconel. For moist gas tantalum is suitable Most common metals Cast iron and stainless steel <120°C, steel <175°C, Inconel, nickel and platinum <400°C Most common metals... 

Such binary borides (p. 145), carbides (p. 297) and nitrides (p. 417) as are formed have been referred to already. The ability of the metals to absorb molecular hydrogen has also been alluded to above. While the existence of definite hydrides of nickel and platinum is in doubt the... 

Palladium forms clusters of these types far less readily than nickel and platinum, unless they are stabilized by o-donor ligands such as phosphines. This may be due to the lower energy of Pd-Pd bonds as reflected in the sublimation energies, 427, 354 and 565 kJ mol for Ni, Pd and Pt. 

Most common metals Cast iron and stainless steel <120 C, steel =s175°C, Inconel, nickel and platinum 400°C Most common metals Glass, stainless steel, copper, Monel or nickel 200 C. At higher temperatures only nickel and Monel are recommended Glass, stainless steel. Teflon Hypalon, aluminium Tygon PVC and polythene... 

Inconel, nickel and platinum 400°C O Most common metals... 

This procedure works well for tetraalkylammonium salts of nickel and platinum complexes, e.g.,... 

Beyond palladium, it has recently been shown that isoelectronic metal complexes based on nickel and platinum are active catalysts for diyne reductive cyclization. While the stoichiometric reaction of nickel(O) complexes with non-conjugated diynes represents a robust area of research,8 only one example of nickel-catalyzed diyne reductive cyclization, which involves the hydrosilylative cyclization of 1,7-diynes to afford 1,2-dialkylidenecyclohexanes appears in the literature.7 The reductive cyclization of unsubstituted 1,7-diyne 53a illustrates the ability of this catalyst system to deliver cyclic Z-vinylsilanes in good yield with excellent control of alkene geometry. Cationic platinum catalysts, generated in situ from (phen)Pt(Me)2 and B(C6F5)3, are also excellent catalysts for highly Z-selective reductive cyclization of 1,6-diynes, as demonstrated by the cyclization of 1,6-diyne 54a.72 The related platinum bis(imine) complex [PhN=C(Me)C(Me)N=Ph]2Pt(Me)2 also catalyzes diyne hydrosilylation-cyclization (Scheme 35).72a... 

Although no efficient bis-silylation reaction for aldehydes and ketones with acyclic disilanes has been established, highly strained cyclic disilanes add to C=0 bond in a 1,2-fashion in the presence of nickel and platinum catalysts (Equations (44) and (45)).83 128... 

Gold occurs as an alloy with copper, nickel and platinum group metals. Typically contains low amount of gold... 

Jiang SP and Badwal SPS. Hydrogen oxidation at the nickel and platinum electrodes on yttria-tetragonal zirconia electrolyte. J Electrochem Soc 1997 144 3777-3784. 

That diolefins play a role in benzene formation has also been shown over over a nickel-on-alumina catalyst. Product composition from 1-heptene as a function of the catalyst amount is shown in Fig. 3. This points also to diene intermediates 50). The same was found with carrier-free nickel and platinum 51). 

A variation of the thermal elimination of an alcohol from the neutral 2-alkoxy-1,2-dihydro-l//-imidazole is the preformation of a chelate vic-bisamine complex which is subsequently attacked by an ort/io-ester to form the desired NHC complex. This principle has been shown with nickel and platinum [Eq. 

Only in homoleptic M(L)2 (L = 1,3-dimesitylimidazolin-2-ylidene) of zero-valent nickel and platinum significantly shorter metal-carbon bonds for NHCs and, thus, metal-to-ligand back donation can be observed. The Ni-C bond length is about 0.15 A shorter than in [Ni(CO)2(L)2] (L = 1,3-dimesitylimidazolin-2-ylidene) which cannot be explained exclusively by the change of the coordination number. 

An alternative method of synthesis consists of preparing (+) 2-aminobutanol (34.1.3) by redncing ethyl ester of L-2-aminobutyric acid hydrochloride with hydrogen nsing simnlta-neonsly Raney nickel and platinum oxide catalysts. This gives pure (+) 2-aminobutanol. Reacting this with 1,2-dichloroethane in the presence of sodium hydroxide gives the desired ethambutol (34.1.4) [16,17]. 

Nickel-platinum bimetallic catalysts showed higher activity during ATR than nickel and platinum catalysts blended in the same bed. It was hypothesized that nickel catalyzes SR, whereas platinum catalyzes POX and, when they are added to the same support, the heat transfer between the two sites is enhanced [59, 60]. Advanced explanations were reported by Dias and Assaf [60] in a study on ATR of methane catalyzed by Ni/y-Al203 with the addition of small amounts of Pd, Pt or Ir. An increase in methane conversion was observed, ascribed to the increase in exposed Ni surface area favored by the noble metal under the reaction conditions. 

British chemist Smithson Tennant Brittle metal found chiefly in ores also containing nickel and platinum its alloys used in manufacturing electrical contacts and fountain pen nibs. 

Carbonylation of Methyl Acetate on Ni/A.C. Catalysts. Table II shows the catalytic activities of nickel and platinum group metals supported on activated carbon for the carbonylation of methyl acetate. Ruthenium, palladium, or iridium catalysts showed much lower activity for the synthesis of acetic anhydride than the nickel catalyst. In contrast, the rhodium catalyst, which has been known to exhibit an excellent carbonylation activity in the homogeneous system (1-13), showed nearly the same activity as the nickel catalyst but gave a large amount of acetic acid. 

Examples of coordination complexes of pyridine with metals are legion and only a few can be mentioned here. Pyridine is a ligand in square complexes of gold (AuEt2Br-py) and copper (Cupy2-Cl2). The cobalt complex CoCLrpy2 has an octahedral structure. Nickel and platinum can coordinate with four pyridine molecules (30). 

On the other hand, some of Suhrmann s electrical resistance measurements on nickel and platinum films and Eischens observations, of the effect of Hj on the infrared spectrum of chemisorbed CO on platinum, referred to earlier, suggest electron-transfer from hydrogen to the metal, i.e., adsorption of positive ions. 

X-ray diffraction studies on salts of the nickel and platinum carbonyl dianions [M3(CO)3(m2-CO)3] 2 (M = Ni, Pt) showed that these... 

The paper deals with some new data concerning the state of the metal after reduction and the catalytic functions of zeolite catalysts containing nickel and platinum. By using the molecular sieve selectivity in the hydrogenation of mesitylene it has been proved that metal (platinum) is contained in the volume of the zeolite crystal. The temperature dependence of the formation of nickel crystals was investigated. The aluminosilicate structure and the zeolite composition influence mainly the formation of the metal surface which determines the catalytic activity. In the hydrocracking of cumene and disproportionation of toluene a bifunctional action of catalysts has been established. Hydrogen retarded the reaction. 

Feolite catalysts modified by transition metals are interesting and difficult subjects to study. In one of the first studies of zeolites as catalysts, Rabo and co-workers (1) used a zeolite catalyst containing 0.5% platinum for isomerization of n-paraffins. In this reaction the metal-zeolite system acted as a typical representative of the bifunctional catalysts. Studies of zeolites modified by transition metals ( 2, 3, Jf) showed that their polyfunctional properties are determined by the structural and chemical properties of the zeolite and by the state of the metal in it. In this paper we discuss new data on the metal state after reduction as well as the catalytic functions of zeolite catalysts containing nickel and platinum. 

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