ISSN:
0030-4921
Keywords:
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Carbon-13 relaxation times, T1, have been measured for ten cobalt(III)-cyclohexanedione dioxime complexes: CH3CH2—Co(Niox)2-p-R-pyridine [R=H, N(CH3)2, CH3, C2H5, C(CH3)3, Cl, Br, CN and COCH3] and CH3CH2—Co(Niox)2-3-N-methylimidazole. The values obtained have been rationalized by making assumptions on the length of the metal - hetrocyclic nitrogen bond. The internal rotation around the axial Co—N (heterocyclic) bond is faster for the 3-N-methylimidazole ligand than for the pyridine ligands. Correlations of the T1 values with the σ-donor and π-acceptor character of the pyridine ligands were attempted. The interpretation of the results suggests the existence of π-back-bonding from the metal to the N-1 pyridine nitrogen atom, in agreement with the results of other workers. This conclusion, however, was not supported by the use of the para-C chemical shift as a criterion for back-bonding in pyridine-transition metal complexes.
Additional Material:
1 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/mrc.1270200103
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