The rate of water exchange on Ru(NH3)5OH23+in aqueous CF3SO3H (0.01 mol L_I) is characterized by k298.2= 2.30 X 10-4s-1, ΔH* = 91.5 kJ mol-1, ΔS* = -7.7 J K-1mol-1, and ΔV* = -4.0 cm3mol-1. The order of lability of M(NH3)5OH23+in water exchange is (M=) Ru > Cr > Rh > Co » Ir and is governed by ΔH*. For substitution reactions of metal complexes involving “hard” leaving groups, the lability sequence first < second > third transition series may be general. For a series of related aqua complexes such as M(NH3)5OH23+, variations in ΔV* for water exchange and the molar volume of the complex as M is changed are largely compensatory, so that the molar volume of the transition state varies relatively little. This reflects reduced accessibility of the complex to associative attack as the central ion becomes smaller.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry