59Co second-order quadrupolar effects in the 13C cross-polarization magic angle spinning NMR spectra of the cobaltocenium salts [Cp*2Co]+[PF6]− and [Cp*CpCo]+[PF6]−
✍ Scribed by Henrike Heise; Frank H. Köhler; Eric B. Brouwer; Robin K. Harris; Stefan Steuernagel
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 102 KB
- Volume
- 37
- Category
- Article
- ISSN
- 0749-1581
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✦ Synopsis
The cobaltocenium ions [Cp Ł 2 Co] C , [Cp Ł CpCo] C , [Cp 2 Co] C and [ EtC 5 H 4 2 Co] C Cp Ł D C 5 Me 5 ; Cp D C 5 H 5 were studied by 13 C cross-polarization magic angle spinning NMR spectroscopy. The ring carbon signals of [Cp Ł 2 Co] C [PF 6 ] and [Cp Ł CpCo] C [PF 6
] showed splitting patterns which are a signature of the hitherto unknown 59 Co, 13 C dipolar coupling. In contrast, a unique signal was found for the remaining cations. The dependence of the patterns on the field, the rotor spinning rate and the temperature was investigated, and full-matrix diagonalization treatment was used to fit the spectra. The patterns were better resolved at lower fields and to some extent at lower spinning rates. Self-decoupling was observed for [Cp Ł CpCo] C [PF 6 ] above 360 K. Visual fitting yielded dipolar and indirect isotropic 59 Co, 13 C coupling constants of 530 and 40 Hz, respectively. When the counter ion of [Cp Ł CpCo] C was changed from [PF 6 ] to Cl or [TCNE] 2 the dipolar coupling pattern was not present, probably because of self-decoupling.