Of palladium compounds

Addition-elimination reactions of palladium compounds with olefins... 

Hydrosilanes react with butadiene by the catalysis of palladium compounds, but the nature of the reaction is somewhat different from that of the telomerization of other nucleophiles described before. Different products are obtained depending on both the structure of silanes and the reaction conditions. Trimethylsilane and other trialkylsilanes reacted with butadiene to give the 1 2 adduct, l-trialkylsilyl-2,6-octadienes (65), in high yield (98%) (62-64). Unlike other telomers which have the 1,6-octadienyl chain, the telomers of silanes have the 2,6-octadienyl chain. As catalysts, Pd(PPh3)2 (maleic anhydride), PdCl2(PhCN)2, PdCl2, and 7r-allylpalladium chloride were used. Methyldiethoxysilane behaved similarly to give the 1 2 adduct. 

Palladium is not combustible except as fine powder or dust. Several of palladiums compounds are oxidizing agents, and some react violently with organic substances. 

HPS was developed by the Laboratory of Sorption Processes (INEOS RAS). It was synthesized by the introduction of methylene bridges between neighboring phenyl rings of linear polystyrene, thus the porous structure was obtained. Preparation of palladium nanoparticles occurred by the adsorption of freshly prepared Na2[PdCl4] solution (Na2[PdCl4] is hydrolyzed in time) into the HPS matrix. The reduction of palladium compound by hydrogen led to the formation of palladium nanoparticles. 

As with many other examples of palladium compounds containing oxygen donors, alkoxide complexes have very rarely been isolated. Two compounds which have been obtained are frfl/is-[Pd(OMe)(CN)(PEt3)2]142 and the methoxide-bridged dimer [Pd2(ju-OMe)2(2,2,6,6-tetramethylheptanedionato)2].143... 

M. J. H. Russell, The advantageous use of palladium compounds in organic syntheses formation of carbon-carbon bonds , Plat. Met. Rev., 1989, 33,186-192. 

Addition-Elimination Reactions of Palladium Compounds with Olefins... 

The addition-elimination reactions of palladium compounds with olefins provide new routes to a wide variety of vinyl and allyl substitution products and, in some instances, saturated products. Many of these reactions cannot be achieved as easily in other ways. The investigatons in this field are just beginning but already it is clear that the reactions are of considerable commercial as well as laboratory use. 

In addition to the head-to-head cross-coupling reactions, it has been discovered that the reaction of phenyl or 1-alkenyl iodides with (E)-l-alkenyl-l,3,2-benzo-dioxaboroles produces the head-to-tail cross-coupling products, 2-phenyl-1-alkenes or 2-alkyl-1,3-alkadienes, respectively (Eq. 107) The reaction is profoundly affected by catalytic quantities of palladium compounds (Pd black prepared by reduction of Pd(OAc)j with diborane is especially effective) in the presence of tri-ethylamine. 

The first important application of palladium compounds for industrial and laboratory syntheses was the oxidation of alkenes to carbonyl compounds, vinyl acetates, and related... 

Catalytic hydroboration is a new methodology of great synthetic potential. The reaction is usually carried out with catecholborane in the presence of rhodium, palladium, iridium and ruthenium compounds.2 In contrast to olefins, very little is known on catalytic hydroboration of conjugated dienes and enynes. Our earlier studies on the uncatalyzed monohydroboration of conjugated dienes,6 reports on the hydroboration of 1-decene with catecholborane catalyzed by lanthanide iodides,7 and monohydroboration of 1,3-enynes in the presence of palladium compounds,8 prompted us to search for other transition metal catalysts for monohydroboration of conjugated dienes and enynes 9 10... 

Two common processes, called oxidative addition and reductive elimination, dominate many reactions of palladium compounds. 

The briefly discussed specific features of the stages of hydrolysis and reduction of palladium compounds are in many respects coincided for all three versions of Pd/ C synthesis discussed in the present section. 

Alcohols and amines add also to acetylenic compounds in the presence of palladium compounds to form intermediates for syntheses of heterocycles, e. g., furans and pyrroles [135]. 

Since the reactions described in this chapter proceed with a catalytic amount of palladium compounds they are more useful than the stoichiometric reactions. 

The monoalkyl complexes TiR(OPr )3 (R = Me, Ph) give cross-coupling reaction products with aryl triflates and halides, in the presence of catalytic amount of palladium compounds.292 Titanate compounds MfTiRCOPr1) produce analogous reactions.293... 

Diazomethane generateti in the presence of palladium compounds has been shown to undergo addition to the double bond of the norbornene fragment of the cyclopentadiene dimer, e.g. formation of 14 and This was attributed to the formation of a 7t-alkene complex of... 

Organometallic Compounds in Industry, Topics in Current Chemistry, Vol. 16, Issue 3-4, Springer-Verlag (reactions of palladium compounds with olefins (R. F. Heck) organometallic catalysts for olefin polymerization and rubber production (A. Gumbolt and H. Weber)(. 

As a consequence of the reduction/oxidation stages during Pd cluster formation some important intermediates could be missed because of general lability of palladium compounds. In this context, it was of interest to follow analogous chemical transformations, using platinum complexes as an example because platinum is... 

Figures 4 and 9 can also be used for a comparative analysis of the SAr2-type reactivity of Pd alkyl complexes vs. their Pt analogs. The former are expected to react at much faster rates. The major reasons for that are (1) a greater kinetic lability of palladium compounds compared to their platinum counterparts that would increase the rate of reductive elimination from Pd " intermediate 4 (Fig. 4, step a 2) and lower the energy of the transition state TSd (Fig. 9), and (2) greater oxidizing power of Pd compared to Pt. The latter factor would decrease the activation barrier for the step a i and the energy of the transition state TSs- Some available reports on C(sp )-0 reductive elimination from presumed high valent palladium intermediates are consistent with this analysis [10, 28].

The second stage of investigation is the determination of the metallocomposite s phase composition, the characteristics of the obtained layer (thickness, compactness) and the sizes of particles and crystallites. The typical scheme of film formation by reduction of palladium compounds in 10% polyamidoimine solutions (in THE or A-methylpyrrolidone) with NaBH4 is as follows [71]. The first stage involves mixing components to attain MX uniform distribution in solution, probably obtaining chelate structures (Fig. 8-6, points). 

The influence of different classes of palladium compounds was also investigated (Table 2). Pd(II)- and Pd(0)-complexes, neutral and ionic palladium species as well as mono- and dinuclear palladium compounds were applied as catalyst precursors. 

It should be noted that extreme care should be exercised when designing catalytic systems for type 1 reactions and in interpreting the results. As soon as these reactions are effectively catalysed by trace amounts of almost any palladium precursor, the nature of catalytically active species cannot be reliably established. Hence, the effects and the real role of potential components of the catalytic system are in question. As a result, the suggestion of catalytic reactions in the absence of deliberately added precatalysts or in the presence of palladium compounds, which are well known not to release palladium, is illegitimate [72, 73]. 

For cross-coupling reactions between iodoarenes and stoichiometric amounts of copper acetylides in the absence of palladium compounds, see (a) Castro, C.E. and Stephens, R.D. (1963) J. Org. Chem., 28, 2163 ... 

MSRH221R R. F. Heck, Fortschr. Chem. Forsch., 1971,16, 221-242. Addition-Elimination Reactions of Palladium Compounds with Olefins. III, IV... 

An Advantageous Use of Palladium Compounds in Organic Synthesis. The Formation of Carbon-Carbon Bonds. 

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