| Autor: |
Laila H. El-Sayed, N.James Lees-Gayed, Magdi F. Iskander, G. R. M. Tawfik |
| Rok vydání: |
1989 |
| Předmět: |
|
| Zdroj: |
Inorganica Chimica Acta. 155:243-248 |
| ISSN: |
0020-1693 |
| DOI: |
10.1016/s0020-1693(00)90418-3 |
| Popis: |
The substitution reactions of 1,2-diphenylethane- diylidene bis( S -methylhydrazinecarbodithioate) NN′-SS′ (−2) nickel(II) and palladium(II) complexes with piperidine and morpholine were followed spectrophotometrically in benzene. Two successive steps were observed, the substitution of the first SMe group deactivating the second SMe group. The first substitution step shows third order kinetics, first order in the substrate and second order in the nucleophile. The third order rate constants increase with the greater basicity of piperidine relative to morpholine, and it was noted that the nickel(II) complex is more susceptible to nucleophile catalysis than the palladium(II) complex. The values of activation parameters show that the higher rate of substitution of the palladium(II) complex is due to entropy effects. It was deduced that the initial attachment of the nucleophile on the SMe carbon to give a dipolar intermediate is followed by the rate determining nucleophile catalyzed formation of the monosubstituted product. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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