Multinuclear NMR and infrared spectroscopic study of a series of cis-Mo(CO)4(py-R)2 (Py-R = 3- or 4-substituted pyridine) complexes: Relationship between chemical shifts and infrared force constants and the Taft electron donor/acceptor parameters of the pyridine substituents
✍ Scribed by James W. Box; Gary M. Gray
- Publisher
- John Wiley and Sons
- Year
- 1986
- Tongue
- English
- Weight
- 762 KB
- Volume
- 24
- Category
- Article
- ISSN
- 0749-1581
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✦ Synopsis
Poor correlations are normally observed between the chemical shifts of the various NMR-active nuclei in Mo carbonyl complexes of group 15 ligands as the group 15 atom substituents are varied. It is possible to observe good chemical shift correlations and to develop relationships between chemical shift and changes in electron density due to variations in the group 15 atom substituents, provided that this variation does not change the cone angles of these ligands. This is the case for complexes of the type cis-Mo(CO),(py-R), (py-R=3-or 4-substituted pyridine). Good to excellent linear correlations are observed between the chemical shifts of the cis and trans CO "C and "0 resonances and the =Mo resonances in these complexes, and between these chemical shifts and the CO infrared stretching force constants of the complexes. Good to excellent correlations also occur between either the chemical shifts or the CO infrared stretching force constants and either the Taft o,/u, or uR and o, parameters. These correlations provide significant insights into the relationship between the electron donor/acceptor abilities of the pyridine ligands and the NMR and infrared spectra exhibited by the cis-Mo(CO),(py-R), complexes.