Electron spin resonance -active transition metal ions

The chapter Electron Spin Resonance in Catalysis by Lunsford was prompted by the extensive activity in this field since the publication of an article on a similar subject in Volume 12 of this serial publication. This chapter is limited to paramagnetic species that are reasonably well defined by means of their spectra. It contains applications of ESR technique to the study of adsorbed atoms and molecules, and also to the evaluation of surface effects. The application of ESR to the determination of the state of transition metal ions in catalytic reactions is also discussed. 

In the reduction of acetylene with molybdothiol and molybdoselenol complex catalysts, the effects of structural variation in ligands, variety of coordination-donor atom, kind of transition-metal ion, and other factors have been surveyed systematically. These factors have profound effects on the catalytic activity. The Mo complexes of cysteamine (or selenocysteamine), its N,N-dimethyl derivative, and its /3-dimethyl derivative give ethylene, ethane, and 1,3-butadiene, respectively, as the major product. The Co (I I) complexes of cysteine and cysteamine show higher catalytic activity than do the corresponding Mo complexes, and the order of the activity in the donor atom, namely S >Se 0 in the Co(II) complexes is consistent with that in the Mo complex systems. On the basis of electron spin resonance (ESR) features of these Mo complex catalysts, a relationship between their ESR characteristics and catalytic activities is discussed. 

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