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

The characteristic feature of majority d-transition series metals is t heir ability to possess several oxidation states. Some of these oxidat ion 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 stat e can be considered as unusualness of the oxidation state. This paper deals with such oxidation states and with the problem of their stabili zation by complex formation.