Leaving Groups on Inert Metal Complexes with Inherent or Induced Lability
1989; Elsevier BV; Linguagem: Inglês
10.1016/s0898-8838(08)60016-1
ISSN1557-8917
Autores Tópico(s)Radioactive element chemistry and processing
ResumoThe terms ‘labile’ and ‘inert’ represent the two extremes of kinetic reactivity. The solvent molecules in the vicinity of the ion differ in properties from those in the bulk solution. A series of progressively ordered and electro-stricted hydration sheaths surround the ion. This chapter focuses on traditional and simple inert metal-ion complexes, mainly octahedral, in which the rate of displacement of at least one ligand permits it to be defined as labile relative to the normal reactivity of complexes of that metal ion. This reactivity may be an inherent property of the ligand as a consequence of poor nucleophilicity. Alternatively, lability may be induced as a result of effects, such as the influence of other nonleaving donors, reactions of the ligand with reagents external to the complex ion, or solvation phenomena. It is convenient to ‘scale’ lability in terms of the rate of substitution of a ligand. A ligand-based order of lability derived for a particular d3 or d6 metal ion can be largely transposed to another, at least as regards the more reactive ligands. Studies of water-exchange reactions of aqua transition metal ions have implied that the structure of the ion in the ground state is an important factor in defining lability. Ion charge plays a role, because more highly charged ions are less likely to exchange rapidly. A great deal of information exists about pentaamine complexes with one leaving group, particularly for cobalt(III) but also for chromium(III) and other metal ions.
Referência(s)