| Autor: |
Charles L. Watkins, Marvin E. Harris |
| Rok vydání: |
1978 |
| Předmět: |
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| Zdroj: |
Journal of Inorganic and Nuclear Chemistry. 40:1769-1775 |
| ISSN: |
0022-1902 |
| Popis: |
The effect of the CF3 group upon substitution for a CH3 group is noted in three different solution studies of acetylacetone (AA), trifluoroacetylacetone (TFA), and hexafluoroacetylacetone (HFA) and their corresponding metal complexes. The lability of dimethyl sulfoxide (DMSO) in exchanging from the axial positions of Ni(AA)2 complexes is dramatically altered by substitution of CF3 groups with k‡( AA )>k‡( TFA )>k‡( HFA ) . The diminution in rate of exchange can be explained by the electron withdrawal of the CF3 group. A good fit of the rate constants to the Hammett equation is noted. The substitution of a CF3 group for a CH3 group causes the bromination of Al(TFA)3 by N-bromosuccinimide to be about 2800 times slower than Al(AA)3(k = 6.7 ± 0.5 sec−1 at 25°C). The 13C and 1H NMR chemical shifts of AA, TFA and HFA were measured and compared with electron densities for the three compounds calculated by the INDO formalism. The 1H and methine 13C shifts show a linear correlation with electron density. The other 13C chemical shifts can best be explained by assuming that AA is quasi-aromatic and the paramagnetic effect is dominant. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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