Palladium complexes activation parameters

Activation parameters for the anation by chloride of the sterically hindered [Pd(MeEt4dien)(OH2)] + have been determined using a newly developed high-pressure stopped-flow instrument for moderately fast reactions. A negative activation volume and a zero activation entropy are compatible with an associative mechanism, probably 7a. This study is the first in a series in which the effect of pressure on such relatively fast reactions will be studied. A summary of published and current work on pressure effects on the kinetics of sterically hindered palladium(ii) complexes by the Frankfurt group has appeared. ... 

Table Rate constants (25 °C) and activation parameters for anation and aquation reactions of palladium(ii) and platinum(n) complexes from reference 60). Ionic strength 1.00 mol 1 (Pd) and 0.50 mol 1 (Pt). Values of in kcal mol (with standard deviation 1). Values of A5 in cal mol with standard deviation 3)...

Aryl iodides add cleanly to zero-valent PI13P (orL) complexes of palladium. The kinetics and activation parameters support a simple concerted oxidative addition process as in (126), preceded by (125). A... 

A large number of heterogeneous catalysts have been tested under screening conditions (reaction parameters 60 °C, linoleic acid ethyl ester at an LHSV of 30 L/h, and a fixed carbon dioxide and hydrogen flow) to identify a suitable fixed-bed catalyst. We investigated a number of catalyst parameters such as palladium and platinum as precious metal (both in the form of supported metal and as immobilized metal complex catalysts), precious-metal content, precious-metal distribution (egg shell vs. uniform distribution), catalyst particle size, and different supports (activated carbon, alumina, Deloxan , silica, and titania). We found that Deloxan-supported precious-metal catalysts are at least two times more active than traditional supported precious-metal fixed-bed catalysts at a comparable particle size and precious-metal content. Experimental results are shown in Table 14.1 for supported palladium catalysts. The Deloxan-supported catalysts also led to superior linoleate selectivity and a lower cis/trans isomerization rate was found. The explanation for the superior behavior of Deloxan-supported precious-metal catalysts can be found in their unique chemical and physical properties—for example, high pore volume and specific surface area in combination with a meso- and macro-pore-size distribution, which is especially attractive for catalytic reactions (Wieland and Panster, 1995). The majority of our work has therefore focused on Deloxan-supported precious-metal catalysts. 

Polymer supported Palladium(II) complex catalyst was synthesised using chloromethylated styrene-divinyl benzene copolymer as a support by sequential attachment of glycine and a metal salt solution. It was characterized using various methods such as IR, UV-Vis, ESR, DTA-TGA, SEM and surface area measurement. Swelling studies, moisture content and bulk density have also been investigated. The catalytic activity of the catalyst was tested for the oxidation of toluene. The effect on it of various parameters has been seen. The recycling efficiency has also been studied. 

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