Thermal stability of Pd(1,4-bis(2-hydroxyethyl)piperazine)Cl₂ and its role in the catalysis of base hydrolysis of α-amino acid esters

Abstract

Pd(BHEP)Cl₂ was synthesized and characterized (BHEP = 1,4-bis(2-hydroxyethyl)piperazine). The complex decomposes in two steps, leaving a residue of palladium metal. Amino acid ester (L) reacts with [Pd(BHEP)(H₂O)₂]²⁺ (BHEP = 1,4-bis(2-hydroxyethyl)piperazine), giving mixed-ligand complexes, [Pd(BHEP)L]²⁺. The kinetics of hydrolysis of [Pd(BHEP)L]²⁺ have been studied by pH-stat technique, and rate constants were obtained. Rate acceleration observed for glycine methyl ester is high. The effect with methionine methyl ester is much less marked, as the mixed-ligand complexes with these ligands do not involve alkoxycarbonyl donors. Possible mechanisms for these reactions are considered.

Graphical abstract

The thermal stability of Pd(BHEP)Cl₂ complex was investigated. The role of the complex in the catalysis of amino acid esters was studied.

Keywords:

• 1,4-Bis(2-hydroxyethyl)piperazine
• Thermal stability
• Amino acid ester hydrolysis
• Pd(II)
• pH-stat technique

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

Dedicated to Prof. Rudi van Eldik on the occasion of his 70th birthday.