Transition-state volumes in solvent exchange. Water exchange on the aqueous aquapentaammineruthenium(III) ion

Hideo Doine, Koji Ishihara, H. Roy Krouse, Thomas W. Swaddle

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The rate of water exchange on Ru(NH3)5OH2 3+ in aqueous CF3SO3H (0.01 mol L-1) is characterized by k298.2 = 2.30 × 10-4 s-1, ΔH* = 91.5 kJ mol-1, ΔS* = -7.7 J K-1 mol-1, and ΔV* = -4.0 cm3 mol-1. The order of lability of M(NH3)5OH2 3+ 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)5OH2 3+, 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.

Original languageEnglish
Pages (from-to)3240-3242
Number of pages3
JournalInorganic Chemistry
Issue number20
Publication statusPublished - 1987
Externally publishedYes


ASJC Scopus subject areas

  • Inorganic Chemistry

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