Original scientific paper

The Kinetics of Aquation of Amminepentaaquachromium(III) Ion. A Comparison with Unsaturated Amine Ligands

A. Bakač ; Institute »Ruder Boskovic«, Zagreb, Croatia, Yugoslavia
V. Butković ; Institute »Ruder Boskovic«, Zagreb, Croatia, Yugoslavia
M. Orhanović ; Institute »Ruder Boskovic«, Zagreb, Croatia, Yugoslavia

Abstract

The aquation of amminepentaaquachromtwn(III) ion was
studied as a function of acidity and temperature at ~t = 1.0 M
(HCl04 + NaCl04). The rate law is of the form - dln [Cr(H20)s
(NH3) 3+]/dt = k0 + k_1/[W]. The entha1py (kcal mol-1) and entropy
(cal mo1-1 K-1) of activation for the acid-independent path are
27.8 and - 5.3, and for the acid-inverse path 34.8 and 7.0. The
corresponding specific rates extrapolated to 25 °c are 1.8 x 10-9 s-1
and 7.0 X 10-12 M s-1• Cr(H20)5(NH3) 3+ aquates significantly faster
than expected on the basis of the linear correlation between
- log k 0 and pKa of the free ligands established for the analogous
complexes with a series of substituted pyridine ligands. Implications
of this observation are discussed.

Keywords

Hrčak ID:

196486

URI

https://hrcak.srce.hr/196486

Publication date:

20.2.1976.

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