The cleavage of alkyl zinc bonds by metallic and organometallic halides

• Main Author: Rolfe, Peter Herbert
• Published: University of Surrey 1965
• Subjects: 540
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.751637

The possible mechanisms by which an alkyl group may transfer from one metal to another have been reviewed, together with evidence for these mechanisms. The nature and properties of the organic derivatives of the Group II metals have been reviewed, with particular reference to the alkylmetal halides. In the present work the relative rates of reaction of dimethylzinc, diethylzinc and di-n-propylzinc with phenylmercuric chloride were found to be in the order Me<Zn (100) < Et<Zn (450) < n-Pr<Zn (1660) in refluxing diethyl ether, by competition experiments in which mixtures of two dialkyl zincs were allowed to react with a deficiency of phenylmercuric chloride. The mechanism of the reaction of a dialkylzinc with phenylmercuric chloride under these conditions is suggested as being an SEi one, involving a closed, four-membered, transition state. The same dialkylzincs reacted at the same rate with phenylmercuric chloride in tetrahydrofuran in similar competition experiments. The reaction of diethylzinc with phenylmercuric chloride was too fast to be followed kinetically, in both solvents. Similarly the reactions of phenylmercuric iodide, ethylmercuric iodide and mercuric iodide with tetrahydrofuran solutions of "ethylzinc iodide" were too fast to follow kinetically. Investigations into the nature of "ethylzinc iodide" solutions have shown that monomeric EtZnI does exist in both ethereal and tetrahydrofuran solutions. The existence of EtZnBr in tetrahydrofuran is suggested. In these studies use was made of both N.M.R. spectroscopy and the fact that it was found in the present work that N,N,N',N' tetramethylethylene-diamine forms 1 : 1 solid complexes with these ethylzinc halides.