Oxidative Addition Oxad Reactions

An oxidative addition reaction occurs when there is an increase in oxidation state of a metal that is accompanied by a simultaneous increase in its coordination number. Numerous examples of oxidative addition (sometimes referred to as oxad) reactions have already been presented for nonmetallic elements including the following  

Each of these reactions involves an increase in the oxidation state of the central atom and the formation of additional bonds to that atom. In this chapter, the discussion of such oxad reactions will be limited to those involving transition metals in complexes. An interesting reaction of this type involving hydrogen is the following  

In this reaction, Ir is oxidized from the +1 oxidation state to +3 during the addition of a hydrogen molecule. When coordinated to the metal, hydrogen is considered to be coordinated as hydride ions, FT. Thus, hydrogen has been added by increasing the coordination number of Ir to 6, and the metal has been oxidized to +3. A general oxad reaction can be represented as 

The addition of oxygen in the following oxad reaction is slightly different because when an oxygen molecule adds to the complex, the atoms do not become separated  

In this complex, the oxygen molecule behaves as if it is bonded to the metal in cis positions 

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Oxidation-addition (oxad) reactions of this type also occur with other compounds as shown in the following examples ... 

This type of reaction involves both oxidation and addition of groups, so it is known as an oxad reaction. Alkyl derivatives of PC13 can be prepared by the reactions with Grignard reagents and metal alkyls illustrated in the following equations ... 

Oxidative addition is a process by which an atom is simultaneously oxidized and the number of bonds to it is increased as groups are added. The term oxad is used to denote this type of reaction. This type of process is not limited to coordination compounds, and it is easy to find numerous examples in other areas of chemistry. The following examples and many others can be found in earlier chapters of this book ... 

A reaction in which an atom is oxidized at the same time that it adds groups is often referred to as an oxidization-addition reaction (abbreviated oxad). A reaction of this type is... 

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