Catalytic effects of metal chelate compounds.

This paper is essentially a progress report on the developments in the field of metal chelate catalysis since the first review of this subject fifteen years ago'. For the purpose of defining the scope of this field, metal chelate catalysis is considered to include any reaction that is altered or modified by metal ions through chelate ring formation, as well as reactions of metal chelates themselves. The relatively narrow definition of catalysis, in which the catalytic substance remains unaltered at the end of each reaction cycle or sequence thus constitutes oniy a part of the overall topic under discussion. The catalytic reactions which do not fit this specific definition may be considered as being "promoted" or "inhibited" by metal chelate ring formation.