Thermodynamic properties of transition metal compounds and coordination complexes: I. The heats of hydration of divalent cations in the series Ca2+ - Zn2+

✍ Scribed by G. C. A. Schuit

• Publisher: Elsevier Science
• Year: 2010
• Tongue: English
• Weight: 346 KB
• Volume: 81
• Category: Article
• ISSN: 0165-0513
• DOI: 10.1002/recl.19620810103

✦ Synopsis

Abstract

According to the ligand‐field theory the heat of hydration of a transition‐metal ion is the sum of an electrostatic interaction and a ligand‐field stabilization.

An estimate of the latter can be deduced from the spectroscopic Δ‐value. If the experimental heats are corrected for the ligand‐field effects, a steady rise for the residual heats is observed going from Ti^2+^ to Zn^2+^ which is considered an argument for the validity of the theory.

However, in the m.o. approximation the metal d‐electrons are either in the t~2g~ state (non‐bonding in the absence of π‐interaction) or in the antibonding e~g~ state. Hence formally the transition‐metal hydrates can be considered as destabilized with respect to a hypothetical standard state which can be calculated, by making suitable corrections, with help of the spectroscopic Δ‐values. It is shown here that the values so obtained are numerically equal to those given by an empirical equation for cations with the inert gas configuration

— (ΔH~n~) = I + constant

(I is the ionization energy for the formation of divalent cations).