Palladium complexes bipyridyl

Carbon monoxide insertion in a palladium-carbon bond is a fairly common reaction [21]. Under polymerization conditions, CO insertion is thought to be rapid and reversible. Olefin insertion in a palladium-carbon bond is a less common reaction, but recent studies involving cationic palladium-diphosphine and -bipyridyl complexes have shown that olefin insertion also, particularly in palladium-acyl bonds, appears to be a facile reaction [22], Nevertheless, it is likely that olefin insertion is the slowest (rate-determining) and irreversible step vide infra) in polyketone formation. 

The properties of a- or y- zirconium hydrogen phosphate, a synthetic inorganic ion-exchanger material with layered structure, as "heterogenizing" support for carbonylation reactions are still to be studied. Our first studies in this field showed that the Pd(II)-2,2 -bipyridyl complex intercalated in these materials catalyzes the oxidative carbonylation of aniline even though its activity falls with time, because the support slowly loses palladium and deactivates during the catalysis process [2]. 

Intramolecular 1,4-Diacyloxylation An intramolecular variant of the palladiumutilizing dienes with a carboxyl group in the side chain (Scheme 11.16) [75, 76]. Also in this case the stereochemistry of the 1,4-addition can be controlled by variation of the ligand environment. Thus, in the absence of chloride a trans acetoxylactonization takes place, whereas in the presence of a catalytic amount of chloride a cis acetoxylactonization occurs. The catalytic intermediate was isolated and stereochemically assigned as its bipyridyl complex 49 [76]. In the stereochemical assignment, bipyridyl was utihzed... 

Yang H., Gao H., Angelici R.J. Hydrogenation of arenes under mild conditions using rhodium pyridylphosphine and bipyridyl complexes tediered to a silica-supported palladium heterogeneous catalyst. Organometalhcs 2000 19 622-629 and references cited therein. 

Allegedly, the product of the reduction is a bipyridyl palla-dium(0) complex. This is not likely and our personal opinion is that the obtained material is a supported metal palladium catalyst. This is the reason why the paper was included in this review. 

The inclusion of the nitrogen donor atom in an aromatic heterocycle allows the possibility of -bonding with the metal centre, giving these ligands some similarities to tertiary phosphines. Thus pyridyl and bipyridyl ligands stabilize organometallic complexes of palladium (see companion volume).2 ... 

In the above structure, if Ph3P is replaced by a bidentate ligand such as bipyridyl, there results a C-rj, -acetylacetonate complex in which palladium is tr-bonded to a terminal CH2 group. These presumably exist as tautomeric keto and enol forms (equation l).53... 

AUylic alkylations. This complex in combination with 2,2 -bipyridyl (bpy) catalyzes nucleophilic alkylation of allylic acetates and carbonates, but is less active than molybdenum or palladium catalysts. The displacement occurs with retention of configuration, as with Mo and Pd catalysts. However, alkylation occurs almost entirely at the more substituted end of the allylic group, regardless of the nucleophile. 

Complexes of phenanthroline and palladium(II) chloride react with carbon monoxide in aqueous solution to give the stable violet compound [(phen)Pd(C0)2Pd(phen)] 4H20 bipyridyl gives an unstable product (119). The formation of the compound has been suggested as the basis of an analytical method for the determination of carbon monoxide (118). 

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