Mercury compounds, organo reactions

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. 

It is w ell known that many organo mercury compounds of the type RjjHg react with metallic and non-metallic chlorides to form organo-rnetabic derivatives of tlie metals in question. The present authors carried out a considerable number of reactions of this type, with various organometallic compounds, the results of which are showii in Table IV. of the Appendix. 

Sometimes light may he employed instead of heat to eflbet this change, as in the case of the organo-tin compounds. In the formation of organo-mercury compounds by this method, light is indispensable to the reaction t—... 

A related cyclization step is employed in an approach to 4-quinolizidinones through intramolecular amidomercuriation of A-protected amines (194) followed by reaction of the organo-mercury compound (195) with acrylonitrile, deproteetion, and cyclization to (196) and (197) (Scheme 34) <84CC1235>. 

The spectrum of mechanisms of the electrophilic substitution at a saturated carbon atom is very broad [1,72-74]. The bimolecular Se2 exchange reactions in the series of organo-mercury compounds have been studied in the most detailed manner. For these reactions as well as for the Se2 reactions of other organometallic compounds, the derivatives of Li, Mg, B, Sn, Ge, a four-center transition state of XXIV type is assumed ... 

It is expected that endothermic or weakly exothermic organometallic compounds will be the most versatile reagents RM in such reactions. Such compounds are found among the heavy B elements (Hg, Tl, Pb and Bi). Of these the air-stable and readily prepared (though toxic) organo-mercury compounds are the most widely used. Let us consider the heats of reaction between dimethyl mercury and zinc and cadmium ... 

These compounds are the most stable of the three classes of organothal-lium(III) derivatives and have been prepared by a wide variety of classical organometallic procedures. Many exchange reactions of TIX3 (X = Cl, carboxylate) with organo derivatives of boron, mercury, tin, lead, etc., have been shown to result in formation of R2TIX compounds 73, 78), but are of relatively little preparative significance. The most frequently used procedure... 

It seems to be certain that the oxynitration reaction in the presence of mercury salts proceeds through the formation of phenylmercuric nitrate. The isolation of phenylmercuric nitrate from a reaction mixture in dilute nitric acid by several authors (Carmack and his co-workers [135], Titov and Laptev [71], and also Bro-ders [124]) favours this view. If an intermediate nitroso compound is formed in the reaction its formation should be ascribed to the reaction between phenylmercuric nitrate and nitrous acid. This view, based on earlier experiments of Baeyer [136], Bamberger [137], Smith and Taylor [137a], has since been confirmed by Westheimer, Segel and Schramm [138], who considered the nitroso compound formed from an organo-mercuric compound to be the principal intermediate product in the Wolffenstein and Boters reaction. 

Holliday and Taylor (59) have studied the reactions of tetrafluorodi-borane(4) with several organometallic reagents. No evidence was obtained for the formation of organo-substituted diboron compounds. Reaction with diphenylmercury led to reduction of a major fraction of the organometallic to metallic mercury, with formation of difluorophenylborane and BF3.Diethylmercury was reduced similarly, with formation of ethyldi-fluoroborane, BF3, and ethane. With tetravinyltin, the major products... 

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