Palladium preparation

Turkevich, J. and Kim, G., Palladium- preparation and catalytic properties of particles of uniform size, Science, 169, 873, 1970. 

Palladium catalysts are more often modified for special selectivities than platinum catalysts. Palladium prepared by reduction of palladium chloride with sodium borohydride Procedure 4, p. 205) is suitable for the reduction of unsaturated aldehydes to saturated aldehydes [i7]. Palladimn on barium sulfate deactivated with sulfur compounds, most frequently the so-called quinoline-5 obtained by boiling quinoline with sulfur [34], is suitable for the Rosenmund reduction [i5] (p. 144). Palladium on calcium carbonate deactivated by lead acetate Lindlar s catalyst) is used for partial hydrogenation of acetylenes to cw-alkenes [36] (p. 44). 

Reduction of the double bond only was achieved by catalytic hydrogenation over palladium prepared by reduction with sodium borohydride. This catalyst does not catalyze hydrogenation of the aldehyde group [31]. Also sodium borohydride-reduced nickel was used for conversion of cinnamaldehyde to hydrocinnamaldehyde [31]. Homogeneous hydrogenation over tris(triphenylphosphine)rhodium chloride gave 60% of hydrocinnamaldehyde and 40% of ethylbenzene [5(5]. Raney nickel, by contrast, catalyzes total reduction to hydrocinnamyl alcohol [4S. Total reduction of both the double... 

Platinum in a finely divided form is obtained by the in situ reduction of hydrated platinum dioxide (Adams catalyst) finely divided platinum may also be used supported on an inert carrier such as decolourising carbon. Finely divided palladium prepared by reduction of the chloride is usually referred to as palladium black. More active catalysts are obtained however when the palladium is deposited on decolourising carbon, barium or calcium carbonate, or barium sulphate. Finely divided ruthenium and rhodium, usually supported on decolourising carbon or alumina, may with advantage be used in place of platinum or palladium for some hydrogenation reactions. 

The specific property of nickel nanoparticles deposited onto silicon substrates of different types of doping was also clearly manifested in another reaction we studied, hydrogenation of multiple bonds. It is known that the optimal situation for catalysis of processes of this kind is presence of a positive charge on metallic particles [43]. This can be achieved upon deposition of Ni nanoparticles onto p-type silicon. Indeed, experiments did show that the activity of Ni nanoparticles onto p-type silicon exceeds by nearly two orders of magnitude the activity of catalysts based on ultra-dispersed platinum and palladium, prepared by other methods. 

The organic groups in diorgano telluriums coupled when the tellurium compounds were refluxed in acetonitrile in the presence of a stoichiometric amount of palladium prepared in situ from palladium(II) acetate3. 

Occurrence and History of Palladium—Preparation—Physical Varieties Physioal Properties—Permeability to Hydrogen--Occlusion of Canos Occlusion of Hydrogen—Chemical Properties--Catalytic Activity Crystalline Palladium—Colloidal Palladium—Spongy Palladium —Palladium Black —Uses—Atomic Weight—Alloys. 

These have previously been obtained by electrophilic attack on ene-yl complexes [equation (a) Y = CH(C02Me)2, OMe ch = 1J-C5H5 diene = 1,5-cyclooctadiene]1 or by reaction of the compounds (diene)MBr2 with 57-C5H6Fe(CO)2Br (diene = 1,5-cyclooctadiene or 1,2,3,4-tetraphenyl-l,3-cyclobutadiene).2 An example of the former method is given in which the methoxy-cyclooctenyl derivative is used as the substrate and tetrafluoro-boric acid as the electrophile. The substrate is conveniently prepared and used without isolation, and in this way the reaction takes only a few hours, starting with dichloro(l,5-cycloocta-diene)palladium, prepared as described above. 

With aryl halides oxidative addition is often the rate-determining step this is promoted by appropriate ligands such as triarylphosphines. Finely divided palladium metal or ligand-free palladium, prepared in situ by reduction of palladium(II) species, can also be used in weak donor media. Palladium(0) with a triarylphosphine as ligand reacts with aryl halides in the order Arl > ArBr> ArCl. Electron-withdrawing groups on the aryl halide increase the reactivity... 

To obtain the HMC as an active component zero-valent nickel complexes of the general formula - Ni[PRj] (n=2-4), where R was Ph or EtjN, characterized by high activity in oligomerization of lower olefins in homogeneous conditions were taken. Heterogenization of these complexes was conducted by method of ligand exchange. In the Literature there are examples of carbonyl complexes of palladium prepared by this method, which show activity in propylene dimerization [8], However, we have failed to find data on such nickel catalysts in the literature. 

Alkylation. Viologen-supported nanoparticles of palladium prepared from PdCl2 show an activity of promoting alkylation of methyl ketones with alcohols in the air at 100°. A 1,3-cycloaIkanedione undergoes alkylation but the ring is opened. The reaction also requires a base such as Ba(OH)2 H2O or Sr(OH)2 8H20. ... 

Besides the study on Suzuki cross-coupling reactions (Scheme 5) in the ionic liquid 1,3-di-n-butyl-imidazolium tetrafluoroborate ([BBIM][BF4]) catalyzed by palladium prepared in situ in a cleaning bath, Srinivasan and co-workers reported ligand-free Pd-catalyzed couplings between aryl halides and terminal alkyne ... 

The J egishi reaction catalysed by palladium Preparation of 4-nitro biphenyl (224) [48]... 

A soln. of dibenzyl ketoxime in benzene added at room temp, to a soln. of peroxobis(triphenylphosphine)palladium prepared by bubbling O2 for 0.5 hr. into a soln. of tetrakis(triphenylphosphine)palladium in benzene, and the product isolated after 5 min. dibenzyl ketone. Y 98%. - This method is recommended for unsatd. and acid- or base-sensitive compds. F. e. and limitations s. K. Maeda et al., Tetrah. Let. 1974, 797. 

Kosugi M, Shimizu T, Migata T. Reactions of aryl halides with thiolate anions in the presence of catalytic amounts of tetrakis(triphenylphosphine)palladium preparation of aryl sulfides. Chem. Lett. 1978 13 14. 

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