Oxidation or reduction of central atoms

The nitrosyl cation can be used to oxidize metallic palladium in the presence of acetonitrile and generate [Pd(MeCN)4]2+, a reaction described in detail in Chapter 4, Eq. 3.16  

In some cases, a metal ion exhibits different coordination numbers in different oxidation states. It may be possible, then, to take advantage of the change in coordination number to form solvento-complexes. For example, platinum(II) complexes typically exhibit a coordination number of four, whereas, the coordination number is usually six for platinum(IV) complexes. Electrochemical oxidation of [PtCl2(PR3)2] (PR3 = various phosphines) in acetonitrile was once thought to lead to the formation of 

In certain cases solvento-complexes may be prepared by reduction of the central metal atom. Thus, [VO(acacen)], a pentacoordinate compound, is transformed into the hexacoordinate solvento-complex [VCl(THF)(acacen)l by reduction of the vanadium center with [TiCl3(THF)3l in tetrahydrofuran.91 2 

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