Electron spin resonance spectra of four-, five-, and six-co-ordinate cobalt(II) isonitrile complexes, and of the pentacyanocobaltate(II) ion
- 1 January 1968
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc. A
- p. 2918-2927
- https://doi.org/10.1039/j19680002918
Abstract
E.s.r. spectra, taken at X- and Q-band, are presented for solutions at 293°K, and glasses at 77 and 150°K, of a series of low spin cobalt(II) isonitrile complexes Co(CNR)6 2+, Co(CNR)5 2+, Co(CNR)4 2+, and Co(CNR)4X2 2+(X = water, pyridine, or solvent). The spectra of the Co(CN)5 3– ion were also measured in methanol, and in water by a rapid quenching technique. The symmetry of these complexes is C4v or D4h[although the Co(CN)5 3– ion may have C2v symmetry]; the unpaired electron is in the |0〉 orbital. The value of g⊥ decreases from the four- > five- > six-co-ordinate complex, and this may probably be interpreted in terms of a simple geometry change about the cobalt. From a comparison of the glass and the solution spectra, the components of the hyperfine coupling A, and B, have opposite signs, thus κ values for the cobalt are calculated (ca. 0·2 for the six-, and 0·05–0·1 for the five-co-ordinate ions). The lack of 59Co hyperfine splitting in the spectra of the five-co-ordinate ions in solutions may be due to a rapid change from square pyramidal-trigonal bipyramidal geometry. The spectra of the tetrakis(isonitrile) cobalt(II) dihalides show that the contributions from ζσπ dominate the g values, in agreement with an electron being in the |0〉 orbital. Electron delocalisation on the halogen increases as Cl < Br < I.Keywords
This publication has 0 references indexed in Scilit: