13C chemical shifts in the aryl complexes PdX(p-RC6H4)(TMEDA). Is the PdX(TMEDA) fragment a substantial π-donor?
✍ Scribed by Matthias Tschoerner; Roland W. Kunz; Paul S. Pregosin
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 310 KB
- Volume
- 37
- Category
- Article
- ISSN
- 0749-1581
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✦ Synopsis
A series of aryl complexes of the form PdX(p-( 1, R \ OMe, Me, H, CN, RC 6 H 4 )(TMEDA) CO 2 Me, TMEDA \ tetramethylethylenediamine, X \ Br, I) were prepared, together with the derivatives NO 2 , and PdI(2-Me-Their 13C NMR spectra were recorded and showed that (i) PdI(C 6 F 5 )(TMEDA) C 6 H 4 )(TMEDA). the ipso carbon, C-1, with d \ 107.6È162.0, is always shifted to higher frequencies, relative to the model organic compound (ii) C-1 is markedly a †ected by the nature of the p-R substituent, with electron-withdrawing HC 6 H 4 R, groups producing high-frequency shifts, (iii) there is a linear correlation between dC-1 and the Hammett constant with a correlation coefficient R \ 0.998 and (iv) there is no compelling evidence for a large n [ donor e †ect p pf rom palladium into the aryl ring. Screening constants for C-1 in a series of phenyllithium compounds, p-RC 6 H 4 Li, were calculated. There is an excellent correlation (R \ 0.972) of *dC-1 for 1 with *pC-1 for Copyright p-RC 6 H 4 Li.