Kinetics of base hydrolysis of tris‐(1,10‐phenanthroline)iron(II) and of solvolysis of cis‐dichlorobis(1,2‐ethanediamine)cobalt(III) in water + diol mixtures

Abstract

Rate constants for base hydrolysis of the trzs-( 1,lO-phenanthroline)iron(II) cation and for solvolysis of the cis-dichlorobis(l,2-ethanediamine)cobalt(III~ cation have been measured in binary aqueous mixtures containing l,a-ethanediol, 1,2-or 1,4-butanediol, 1,2-or 1,6-hexanediol, 1-propanol, or t-butyl alcohol, at 298.2 K. Kinetics of base hydrolysis of the cobalt(II1) complex have also been monitored in methanol-water and ethanol-water mixtures, again at 298.2 K. The observed reactivity trends are discussed in terms of the hydrophilic and hydrophobic properties of the respective diols. The dominant factor determining reactivity is hydration of the attacking hydroxide or leaving chloride, as is evidenced by the close correspondence between rate constants and transfer chemical potentials for these anions. The role of hydration has also been probed through the determination of activation volumes for these two reactions in 60% 1,4-butanediol.