Octahedral substitution mechanisms and reactive intermediates

The paper reviews and discusses some aspects of substitution of octahedral complexes in aqueous solution. The areas considered primarily are anation, aquation and substitution in labile and kinetically robust systems. The evidence for the existence of intermediates of reduced coordination number, the characteristics and properties of such intermediates and the implications of these properties in the aforementioned processes are considered. A discussion of some primary aspects of base hydrolysis in octahedral complexes is included. The intermediates derived from these processes and details concerning their lifetime and structure are discussed. Finally, the use of such intermediates for synthesis of labile and thermodynamically unstable products is exemplified. The dissociative character of all this chemistry is offset against the comparative absence of nucleophilic characteristics. The point is made that the absence of nucleophilic paths for electronically rich systems should lead more commonly to the observation of electropFiilic reactions and some of the evidence for these is