Colloids palladium

This technique is the most widely used and the most useful for the characterization of molecular species in solution. Nowadays, it is also one of the most powerful techniques for solids characterizations. Solid state NMR techniques have been used for the characterization of platinum particles and CO coordination to palladium. Bradley extended it to solution C NMR studies on nanoparticles covered with C-enriched carbon monoxide [47]. In the case of ruthenium (a metal giving rise to a very small Knight shift) and for very small particles, the presence of terminal and bridging CO could be ascertained [47]. In the case of platinum and palladium colloids, indirect evidence for CO coordination was obtained by spin saturation transfer experiments [47]. 

Michaelis, M. and Henglein, A., Reduction of palladium (II) in aqueous solution stabilization and reactions of an intermediate cluster and palladium colloid formation, J. Phys. Chem., 96, 4719, 1992. 

Schmid, G. et al., Catalytic properties of layered gold-palladium colloids, Chem. Eur. J., 2,1099,1996. 

Bonnemann, H. Brinkmann, R., and Neiteler, P., Preparation and catalytic properties of NR4+-stabi-lized palladium colloids, Appl. Organomet. Chem., 8, 361,1994. 

Moreover, the amphiphilic nonchiral polymer PG-0C(0)Ci5H3i was used by Mecking and coworkers in the preparation of nanometer-sized stable palladium colloids using PdCl2 or Pd(OAc)2. The formation of these palladium colloids was visualized by transmission electron microscopy and in the case of the amphiphilic polymer prepared from a PG scaffold of DPn = 63, a colloid of 5.2 1.8 nm average particle size was obtained. The... 

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. 

Catalyzation with a tin/palladium colloid, acceleration by removal of the tin coating and electroless copper deposition with commercially available products results in an adherent copper layer to the plastic. The plated sample is then heat treated, electroplated with copper to a thickness of 37.5/x and then heat treated again. 

Chauhan BPS, Rathore JS, Chauhan M, Krawicz A (2003) Synthesis of polysiloxane stabilized palladium colloids and evidence of their participation in silaesterification reactions. 1 Am Chem Soc 125 2876-2877... 

Klingelhofer S, Heitz W, Greiner A, Oestreich S, Fgrster S, Antonietti M (1997) Preparation of palladium colloids in block copolymer micelles and their use for the catalysis of the Heck reaction. J Am Chem Soc 119 10116-10120... 

Apart from these examples, nanoparticle-containing ionic liquids can also be used to impregnate a solid support from which the liquid is finally removed.1831 A solution of palladium colloids in [C4Ciim][Tf2N] was added to an orthosilicate and allowed to gelate. Afterwards, the ionic liquid was extracted with acetonitrile and the resulting aerogel used to reduce cinna-maldehyde. 

In addition, other forms of Pd(0) stabilized in less conventional ways should be cited. Catalytically active palladium colloids are obtained by reduction of palladium acetate in DMSO, or in the presence of a number of polymers. " Some of the latter are easy to recycle and avoid the leaching of Pd during the catalytic runs. 

Samples of a palladium colloid were prepared by concentrating the original organosols to l-2 metal concentration (a factor of 5-10) filtering as before, and exposing the concentrated solution to 99 at lat. 

De Vries JG (2006) A unifying mechanism for aU high-temperature Heck reactions. The role of palladium colloids and anionic species. Dalton Trans 3 421... 

A new development is biphasic hydrogenation using solvent-stabilized colloid (SSCs) catalysts [39-41]. Palladium colloid systems, especially, were proven to give high reactivity and selectivity. Best solvents are dimethylformamide and particularly the two cyclic carbonic acid esters, ethylene carbonate and 1,2-propene carbonate. In these solvents sodium tetrachloropalladate - stabilized by a sodium carbonate buffer - is reduced with hydrogen to yield the solvent-stabilized palladium colloid. Transmission electron microscopy of the palladium colloid demonstrates that the colloid particles are spherical with an average diameter of 4 nm. 

The propene carbonate-stabilized palladium colloid is an excellent catalyst for the hydrogenation of a great number of different fatty acids, fatty esters, and triglycerides. Table 2 gives a survey of results with sunflower, palm-kernel and rapeseed oils, acids, and esters. The yield of C18 1 products after hydrogenation is in the range of 86-93%. In all examples the reaction time is very short. 

The immobilized, colloidal palladium catalyst, Si02-(C3H6SH)nPd is reported to induce the Heck reaction [14a] between ethyl iodide and ethyl acrylate. XPS data showed the presence of Pd(Il) on the surface of the colloidal Pd particles, owing to air oxidation this explains the different behavior of this and the Pd/C catalyst. Addition of BujN.HI and iodine greatly reduced the induction period. The catalytic activity of propylene carbonate-stabilized palladium colloids in the Heck reaction has been investigated [14b]. 

P. C. Hidber et al.. Microcontact printing of palladium colloids Micron-scale patterning by electroless deposition of copper, Langmuir, 12, 1375, 1996. 

Beller et al. have shown for the first time that palladium colloids are effective catalysts for the olefination of aryl bromides (Heck reaction). Reetz et al. have studied Suzuki and Heck reactions catalyzed by preformed palladium clusters and palladium/nickel bimetallic clusters and further progress was achieved by Reetz and Lohmert using propylene carbonate stabilized nanostructured palladium clusters as catalysts in Heck reactions. In addition, the use of nanostructured titanium clusters in McMurry-type coupling reactions has been demonstrated by Reetz et... 

Figure 4. High-resolution electron microscopy (HRTEM) of bimetallic, shell structured gold-palladium colloids. The 18-nm gold cores (dark areas) are covered by a Pd shell ca 4-5 nm thick. J...

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