UNUSUAL OXIDATION-STATES OF D-TRANSITION METALS IN COORDINATION-COMPOUNDS

The characteristic feature of majority d-transition series metals is their ability to possess several oxidation states. Some of these oxidation states are quite unstable and these unstable oxidation states are interesting for inorganic and especially coordination chemistry. As a criterion of the stability of the given oxidation state we can choose the existence of aqua-ions of the d-metal in the given oxidation state. The non-existence of the d-metal aqua-ions in a given oxidation state can be considered as unusualness of the oxidation state. This paper deals with such oxidation states and with the problem of their stabilization by complex formation.