Chromium complexes water exchange reactions

The formation of malonate and oxalate complexes from [Cr(OH2)6] + involves rate-determining chromium-water bond breaking in an ion-pair in each case. Activation parameters for these two reactions, for formation of the monoglycine complex, and for water exchange at chromium(iii) are all rather similar. The formation of edta complexes of chromium(iii) is more complicated, involving several water displacement and chelation steps. Rates and activation parameters are reported for the tridentate to quinquedentate conversion ... 

The literature available from the end of the last report (December 1989) to September 1991 is covered in this chapter. A complete revision of the International Union of Pure and Applied Chemistry (lUPAC) " Nomenclature for Inorganic Chemistry has appeared and lUPAC-recommended ligand abbreviations will be used wherever possible. Research activity in chromium chemistry continues at about the same level as in the past, but there are odd surges as new techniques " or complexes become available. As in previous years, the general chemistry of chromium has been reviewed. l Other, more specialist reviews include the spectroscopy of Cr(VI), organochromium(III) chemistry,and macrocyclic complexes of chromium in various oxidation states.Closer to the mechanistic area is a review of the photophysics of chromium(III) complexes and, more specifically, the photochemical water-exchange process in chromium(III) complexes. A summary of new insights into the mechanism of spontaneous and base-catalyzed substitution reactions of inert-metal amine complexes has also appeared. ... 

Ligand field irradiation of chromium(III) complexes leads primarily to substitution reactions/ The most common reaction in aqueous solution is photosubstitution of a ligand by water. One of the earliest studies of photoaquation reactions was the light-induced exchange of water between Cr(H20) and the solvent. The reaction is followed by using isotopically labeled H2O as the solvent, where sequential photosubstitution of the H2O molecules leads to the formation of Cr(H20 )6 (Ref.3) ... 

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