Reactivity trends of hydroxide ion attack on high spin Fe(II) complexes including bromosalicylidene amino acid ligands in some mixed aqueous solvents: Gibb’s Free Energy of Transfer and initial-transition state analysis

Abstract

The kinetics of hydroxide ion attack on bis(bromosalicylidene alanate)iron (II) (bsali), bis(bromosalicylidene phenylalanate)iron(II) (bsphali), bis(bromosalicylidene aspartate)iron(II) (bsasi), (bromosalicylidene histidinate)iron(II) (bshi), bis(bromosalicylidene arginate)iron(II) (bsari) have been reported in different binary aqueous solvent mixtures at 298 K. The observed reactivity trends are discussed in terms of the hydrophilic and hydrophobic forms of the complexes investigated, as well as the transfer chemical potentials of hydroxide ion and the complex. Both the solvent–solute and solvent–solvent interactions have been considered. The hydrophobic character of the complexes studied was manifested by decreasing in reactivity. Solvent effect on reactivity trends of the investigated complexes has been analyzed into initial and transition state components by using the transfer chemical potentials of the reactants and the kinetic data of the studied compounds. The decrease in the observed rate constant values (kobs) of the base hydrolysis of the investigated complexes with increasing of solvent % is dominated by the initial state (IS).

Keywords

• Base hydrolysis
• Kinetics
• Solvolysis
• Chelate
• Gibb’s Free Energy of Transfer
• Initial state-transition state