Condensation Reactions Induced by Coordinately Unsaturated Species

1 Condensation Reactions Induced by Coordinately Unsaturated Species 

For inducing the formation of metal-metal bonds, it is, in general, necessary for the metal atoms to exist in a rather low oxidation state. Especially suitable for the synthesis of metal clusters are therefore electron-deficient fragments in which the metal atoms have the same oxidation state than that they will have in the cluster. These fragments are normally very unstable and labile species. Electron deficiency induces a coordinative unsaturation that in absence of strong donor species will tend to form metal-metal bonds. 

Reduction of Salts of Metals in Normal Oxidation States. In many cases the formation of reactive fragments can be achieved directly from salts of the metals in their normal oxidation states. In these processes the following two steps should be distinguished  

A reduction process to obtain the metal in adequately low oxidation state, and 

The disruption of one or more bonds to produce unsaturated species. 

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