Platinum amides

Because of its solubility, pyrrole can be polymerized in water. With this notable exception, organic solvents are usually employed. Acetonitrile and benzonitrile are the preferred ones because of their high dielectric constants (e = 37 for acetonitrile and e = 25 for benzonitrile) and their stability in a wide potential range (from 2.7 to -3.2 V vs. SCE on platinum). Amides (dimethyl formamide 1.5 to -2.5 V and e = 37), ethers (tetrahydrofuran 2.1 to 3.3 V and e = 7), propylene carbonate (1.7-1.9 V and e = 64), and methylene chloride (1.8 to -1.7 V, e = 9) are also frequently used. 

Heating metallic lithium in a stream of gaseous ammonia gives lithium amide [7782-89-0] LiNH2, which may also be prepared from Hquid ammonia and lithium in the presence of platinum black. Amides of the alkaH metals can be prepared by double-decomposition reactions in Hquid ammonia. For example... 

Condensation of ethyl acetoacetate with phenyl hydrazine gives the pyrazolone, 58. Methylation by means of methyl iodide affords the prototype of this series, antipyrine (59). Reaction of that compound with nitrous acid gives the product of substitution at the only available position, the nitroso derivative (60) reduction affords another antiinflammatory agent, aminopyrine (61). Reductive alkylation of 61 with acetone in the presence of hydrogen and platinum gives isopyrine (62). Acylation of 61 with the acid chloride from nicotinic acid affords nifenazone (63). Acylation of 61 with 2-chloropropionyl chloride gives the amide, 64 displacement of the halogen with dimethylamine leads to aminopropylon (65). ... 

A variety of catalysts including copper, nickel, cobalt, and the platinum metals group have been used successfully in carbonyl reduction. Palladium, an excellent catalyst for hydrogenation of aromatic carbonyls is relatively ineffective for aliphatic carbonyls this latter group has a low strength of adsorption on palladium relative to other metals (72,91). Nonetheless, palladium can be used very well with aliphatic carbonyls with sufficient patience, as illustrated by the difficult-to-reduce vinylogous amide I to 2 (9). 

Reductions of nitronitriles situated to favor interaction are apt to involve both functions (S4,93). Hydrogenation of o-nitrobenzonitrile over either palladium or platinum gave o-aminobenzamide (78), with the amide oxygen transferred from the nitro group (66). On the other hand, l-amino-2-cyanonaphthalene gave the amino amide on reduction over Pt02, but the amino nitrile over palladium (82). 

Hydrogenation of 3 over 10% Pd-on-C led to the expected cyanoamine (4), the amide (5), the lactam (7), as well as 6, in which the nitrile carbon is lost (5. ). The nitrile function is lost before formation of the amine, for 4 resists reduction. A somewhat different distribution is obtained over Pt02, as expected, and accords with the tendency of platinum to produce more intermediate hydroxylamine (82). 

In some molecules, the loss of halogen is unexpectedly facile and may occur extensively even over platinum, as illustrated by reduction of the dihydro-2-benzazepine 4 to 5. The authors (5i) raised the possibility that such facile loss of halogen may involve neighboring-group assistance from the amide moiety. 

The generalized application of the aminolysis of halophosphanes has been the method of choice for the preparation of a wide variety of chiral phosphinous amides by starting from enantioenriched primary amines [36]. The aminolysis reaction occurs efficiently even when the halophosphane is placed in the coordination sphere of a metal, as in the palladium and platinum complexes of the type ds-M(Ph2PCl2)2Cl (M=Pd, Pt) [37,38]. 

Some Pt complexes bearing electron-donating phosphines can also catalyze the hydration of the C=C double bond of acrylonitrile or crotonitrile and yielded P-hy-droxypropionitrile or P-hydroxybutyronitrile respectively besides the corresponding amide (Eq. 6.38) [22, 75], Among the platinum phosphine complexes examined, [Pt(PEt3)3] (26a), carrying less bulky ligands, was the most effective for the hydration of the olefmic bond. The present catalyst system was ineffective for hydration of other olefins, however. 

In a study of the hydrolysis of platinum(II)-nitrile complexes to afford the corresponding amides, the first well-characterized examples of platinum(II) complexes that dimerize spontaneously to form weakly bonded Pt-Pt dimers with an unsupported intermetallic bond have been described.166 For example, treatment of cw-[PtCl2(NCBut)2] with excess KOH affords the amide species cw-[PtCl2 HN=C(OH)But 2], which exists as a dimer (49) both in solution and in the solid state, with a Pt-Pt bond length of 3.165(1) A, as determined by X-ray crystallography. Four... 

Platinum catalyzes the hydrogenation of most functional groups. It will not catalyze the hydrogenation of esters, acids, and amides. 

The reaction of alcohols with CO was catalyzed by Pd compounds, iodides and/or bromides, and amides (or thioamides). Thus, MeOH was carbonylated in the presence of Pd acetate, NiCl2, tV-methylpyrrolidone, Mel, and Lil to give HOAc. AcOH is prepared by the reaction of MeOH with CO in the presence of a catalyst system comprising a Pd compound, an ionic Br or I compound other than HBr or HI, a sulfone or sulfoxide, and, in some cases, a Ni compound and a phosphine oxide or a phosphinic acid.60 Palladium(II) salts catalyze the carbonylation of methyl iodide in methanol to methyl acetate in the presence of an excess of iodide, even without amine or phosphine co-ligands platinum(II) salts are less effective.61 A novel Pd11 complex (13) is a highly efficient catalyst for the carbonylation of organic alcohols and alkenes to carboxylic acids/esters.62... 

Our investigations showed that in mixed melts of eutectic composition carbamide-NH4(K)Cl, the oxidation and reduction of melt constituents take place mainly independently of each other. The anodic process at platinum electrodes in the range of potentials below 0.9V is associated with the direct oxidation of carbamide to secondary and tertiary amide compounds, accumulation of ammonium ions in the melt, and evolution of the same gaseous products as in carbamide electrolysis [8], The cathodic process is accompanied by the formation of ammonia, CO, and C02, i.e. of the same products as in pure- carbamide electrolysis. In contrast to carbamide melt, a large amount of hydrogen appears in the cathode gases of the mixed melt, and in the anode gases of the carbamide-KCl melt, the presence of chlorine has been established at potentials above 0.9V. In the... 

Platinum-Blues and the Related Amidate-Bridged Platinum111 Compounds... 

Structures and Reactivities of Platinum-Blues and the Related Amidate-Bridged Platinum111 Compounds Kazuko Matsumoto and Ken Sakai... 

Akashi and coworkers prepared small platinum nanoparticles by ethanol reduction of PtCl in the presence of various vinyl polymers with amide side chains [49]. These authors studied the effects of molecular weight and molar ratio [monomeric unit]/[Pt] on the particle sizes and size distributions by electron microscopy, and in some cases by the dispersion stability of the Pt colloids. The hydrogenation in aqueous phase of allyl alcohol was used as a model reaction to examine the change in catalytic activity of polymer-stabilized Pt colloids upon addition of Na2S04 to the reaction solution. The catalytic tests were performed in water or in Na2S04 aqueous solution at 25 °C under atmospheric pressure of... 

The enantioselective hydrogenation of prochiral substances bearing an activated group, such as an ester, an acid or an amide, is often an important step in the industrial synthesis of fine and pharmaceutical products. In addition to the hydrogenation of /5-ketoesters into optically pure products with Raney nickel modified by tartaric acid [117], the asymmetric reduction of a-ketoesters on heterogeneous platinum catalysts modified by cinchona alkaloids (cinchonidine and cinchonine) was reported for the first time by Orito and coworkers [118-121]. Asymmetric catalysis on solid surfaces remains a very important research area for a better mechanistic understanding of the interaction between the substrate, the modifier and the catalyst [122-125], although excellent results in terms of enantiomeric excesses (up to 97%) have been obtained in the reduction of ethyl pyruvate under optimum reaction conditions with these Pt/cinchona systems [126-128],... 

STRUCTURES AND REACTIVITIES OF PLATINUM-BLUES AND THE RELATED AMIDATE-BRIDGED PLATINUM111 COMPOUNDS... 

C. Oxidation of Organic Substances Catalyzed by Amidate-Bridged Platinum(III) Complexes... 

II. Syntheses and Structures of Platinum-Blues and Related Amidate-Bridge Platinum"1 Complexes... 

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