Pd oxidant

Reactivity patterns of this in situ method also support the hypothesis that Pd oxidation occurs via the acidic phosphonium. This initial reaction would involve initial formation of a palladium hydride. Such hydride intermediates are usually very reactive due to the weakness of the Pd-H bond, which in turn imparts instability. 

In contrast to [L Pd], oxidative addition of aryl halides on [L Ni] often proceed by single electron transfer mechanism [2, 197]. SN2 and SNAr types of oxidative addition as a step of the catalytic dehalogenation have also been proposed in the literature for low-valent Ti [40, 114], Zr(II) [115], Ru(II) [20, 74, 81, 98],... 

Both the MPT and DTS use CATOX units to destroy VOCs in the gaseous effluent streams. The CATOX units use a Pt/Pd oxidation catalyst. AEA uses a scrubber and filter upstream of the CATOX units to remove phosphorus, fluorine, and chlorine compounds that could poison the catalyst. 

In order to gain a better understanding of the overall Pd° oxidation sequence, Stahl and coworkers recently investigated the protonolysis of two different peroxo Pd complexes, hi the first study, acetic acid was added to (bc)Pd(02), 16 (Scheme 8) [69]. The presumed intermediate hydroperoxo Pd complex, 30, does not build up in this reaction. If only one equivalent of acetic acid is added, 0.5 equivalents of the diacetate complex, 31, is formed together with 0.5 equivalents of unreacted 16. This result impHes that the second protonation step proceeds much more rapidly than the first. 

The selectivity towards FFCA is dependent on the type of catalyst used. For example the maximum yield in the case of Pd catalysts is about 50%, whereas Pt and Ru reach a maximum of 75%. In the case of Pd, oxidation of the aldehyde group as first step of the reaction (leading to HFCA) plays an important role. This might be due to a higher concentration of hydrated HMF present on the Pd surface. Also the catalyst support influences the selectivity of the oxidation. For Pd/Al-N the selectivity towards HFCA is higher than for Pd/C, with the maximum yield of FFCA being almost the same. 

Pd(acac)2/Si02. Daniell, et al, prepared Pd/silica samples using Pd(acac)2 dissolved in tetrahydrofuran under reflux to be subsequently examined by IR of the chemisorbed CO. These researchers examined the influence of the pretreating atmospheres on the nature of the Pd surface (Pd oxidation state and size of Pd particles) created under the prescribed conditions and how this surface would chemisorb the CO probe molecule. The pretreatment atmospheres used for the decomposition of the supported Pd(acac)2 were O2, H2, CO, N2, and... 

Palladium Supported Pd Oxidation of acetylene and acetic acid... 

Fig. 14. Temperature-programmed reduction profiles of Pd/NaY after reoxidation to different temperatures following initial calcination to 500°C and reduction at 500°C. The peak at about 0°C is attributed to the reduction of Pd oxide the peak at about 180°C is attributed to the reduction of redispersed Pd ions in sodalite cages (76).

Palladium salts can bring about oxidative carbonylation of alkenes in the presence of copper(II) salts which can reoxidize Pd° to Pd . Oxidative carbonylation is favored over simple hydroesterification by the presence of bases and by low temperatures (25 C) and low pressures (3-15 bar). The products can be a, -unsaturated esters, dicarboxylic acid esters or -alkoxy esters. By careful optimization of the conditions (25 °C, 4 bar CO, methanol solvent, CuCh reoxidant and sodium butyrate buffer) high yields of diesters can be obtained (equation 35). ... 

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