Exchange reactions palladium® chloride

The preparation of organopalladium compounds by exchange reactions of palladium salts and organo-lead, -tin, or -mercury compounds is apparently not the only way that they can be obtained but it does seem to be the most useful way. Convincing evidence is now available to show that direct metalation of aromatic compounds with palladium salts (palladation) can occur. Since the initial report of Cope and Siekman 32> that palladium chloride reacted readily with azobenzene to form an isolable chelated, sigma-bonded arylpalladium compound, several additional chelated arylpalladium compounds have been prepared. 

The chloro[exo-5-acetoxytricyclo[2.2.1.0 ]hept-enifo-3-yl]dipyridinepalladium complex 17 [prepared from norbornadiene and palladium(II) chloride bisbenzonitrile complex with subsequent substitution and ligand exchange ] underwent exchange with acetoxy(phenyl)mer-cury, analogous to the known exchange reactions between palladium(II) chloride or acetate and phenylmercury salts, to afford a mixture of products, including biphenyl (54%), exo,exo-3,5-diacetoxytricyclo[2.2.1.0 ]heptane (19,20%) and chloro[exo-5-acetoxytricyclo[2.2.1.0 ]-hept-e Jo-3-yl]mercury (18, 57%). 

The reaction between cyclopropane and deuterium has been investigated over pumice-supported palladium, rhodium, and platinum catalysts between 0 and 200°, and the resulting deuteropropanes have been analysed mass-spectrometrically. The exchange reaction between propane and deuterium over these catalysts has been similarly studied. In every case there is extensive multiple exchange, and the distribution of deuterium atoms in the propanes is more characteristic of the metal than of the reacting hydrocarbon. Experiments with the isomeric propyl chlorides confirm that exchange proceeds through the equilibria... 

Lithiopyrimidines, -pyrazines, and -pyridazines have been converted by exchange with zinc chloride into the more stable zinc compounds " for use in palladium-catalysed couplings (section 11.5.2). Magnesium derivatives have been prepared by reaction of 5-bromopyrimidines with n-butylmagnesium bromide and cerium compounds (which give better results than lithiopyrimidines in reactions with enolisable ketones) can be prepared from either bromo- or lithiopyrimidine. ... 

On warming the solution of (LIV) and the phosphine, the green color rapidly disappeared and the products obtained were the octaphenylcyclo-octatetraene (XLIII) and the bis(tert-phosphine)palladium chloride (LXX). (XLIII) presumably arises from the tricyclooctadiene which is formed by coupling of the diradical (LXXI). The ligand-exchange reaction based on this has already been described in Section IV, F none of the cydoocta-tetraene (XLIII) was formed here (59). 

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