Palladium group 12

The direct determination of eight trace impurities (Na, Mg, Ca, V, Mn, Fe, Ni and Ga) in A1203 ceramic based powders by ICP-MS using electrothermal evaporation (ETV) with slurry sampling has been studied by Wende and Broekaert.66 The authors investigated the capability of several palladium group modifiers. Optimum results were obtained with the PdCl2 modifier... 

Other noble metals from the palladium group, e.g. Rh and Ru, only catalyze complete oxidation [72,73],... 

Olefinic compounds will often insert into carbon-transition metal bonds as CO does, and this reaction is an important step in many catalytic syntheses. When this step is combined with an oxidative addition of an organic halide to a palladium(O) complex in the presence of a base, a very useful, catalytic olefinic substitution reaction results (26-29). The oxidative addition produces an organopalladium(II) halide, which then adds 1,2 to the olefinic reactant (insertion reaction). The adduct is unstable if there are hydrogens beta to the palladium group and elimination of a hydridopalladium salt occurs, forming a substituted olefinic product. The hydridopalladium salt then reforms the... 

Other atoms or groups than hydrogen may be lost in the final elimination step. Chlorine (or bromine or iodine) especially is lost easily, in fact in preference to hydrogen when it occurs in positions 3 to the palladium group. 

The halides of the palladium and platinum groups of metals closely resemble in character those of gold, which have already been described. The dihalides of the palladium group are all soluble, save Pdl2, which is prepared by precipitation with potassium iodide. Nitro-hydro-chloric acid yields the higher chloride it remains on evapo-... 

Elements of the palladium group have a very wide range of valency hence they form a large group of compounds. 

As a result of this lanthanide contraction the radius and therewith the properties of the next elements hafnium, tantalum and tungsten are practically the same as those of the elements zirconium, niobium (columbium) and molybdenum which are situated above them. The same phenomenon is shown in the similarity of the metals of the platinum group with those of the palladium group. 

Rylander and Cohn (40) have reported synergistic effects for the use as catalysts simultaneously of two different platinum or palladium group metals in the reduction of various organic compounds. For example, in Fig. 21 are plotted observations oncerning the rate of hydrogenation of... 

In the case of 53, a chair-like pre-transition state conformer 53a is thought to be involved, in which the bulky aryl and palladium groups are pseudo equatorial. This gives rise to the energetically most favourable equatorial conformer 53b, which is transformed into 54a (Scheme 5.6.16). Under identical conditions, in the presence of vinyltri-n-butyltin, the intermediate 53a is intercepted by vinyl transfer (Scheme 5.6.16) showing that this inter-molecular anion capture 54b is significantly faster than the 6-exo-trig cyclization-anion capture. 

Heterometallic clusters containing -allylic palladium groups have been generally synthesized by reaction of an anionic cluster with [Pd(/r-X)( -allyl)]2 (X = halide) in a reaction that resembles a ligand substitution (Equation (31)). The formal oxidation state of Pd in the product cluster is usually different from two, so the reaction can also be considered as a redox transformation Pd-Fe bimetallic clusters, " and also trimetallic Pd-Fe-Fe-Co 82 and Pd-Fe-Ru-Ru, have been prepared in this way. 

Other seleetivity issues can arise during P-hydride elimination. If there is more than one sp -bonded hydrogen atom beta to the palladium group in the olefin adduct, then a mixture of geometric isomers may result. Also, if the hydridopalladium(II) species is not scavenged fast enough by the... 

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