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59 Co second‐order quadrupolar effects in the 13 C cross‐polarization magic angle spinning NMR spectra of the cobaltocenium salts [Cp * 2 Co] + [PF 6 ] − and [Cp * CpCo] + [PF 6 ] −
Author(s) -
Heise Henrike,
Köhler Frank H.,
Brouwer Eric B.,
Harris Robin K.,
Steuernagel Stefan
Publication year - 1999
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/(sici)1097-458x(199908)37:8<573::aid-mrc506>3.0.co;2-n
Subject(s) - chemistry , magnetic dipole–dipole interaction , magic angle spinning , spectral line , spinning , ion , dipole , nmr spectra database , analytical chemistry (journal) , nuclear magnetic resonance spectroscopy , decoupling (probability) , crystallography , coupling constant , stereochemistry , physics , organic chemistry , astronomy , particle physics , control engineering , polymer chemistry , engineering
The cobaltocenium ions [Cp * 2 Co] + , [Cp * CpCo] + , [Cp 2 Co] + and [(EtC 5 H 4 ) 2 Co] + (Cp * = C 5 Me 5 ; Cp = C 5 H 5 ) were studied by 13 C cross‐polarization magic angle spinning NMR spectroscopy. The ring carbon signals of [Cp * 2 Co] + [PF 6 ] − and [Cp * CpCo] + [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 * CpCo] + [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 * CpCo] + was changed from [PF 6 ] − to Cl − or [TCNE] 2− the dipolar coupling pattern was not present, probably because of self‐decoupling. Copyright © 1999 John Wiley & Sons, Ltd.