Decarboxylation and simultaneous reduction of silver(i) β-ketocarboxylates with three types of coordinations

Abstract

A series of silver(I) β-ketocarboxylates were prepared by reaction of β-ketocarboxylic acids with silver nitrate in the presence of diethanolamine. The silver(I) β-ketocarboxylates decomposed over a narrow temperature range to form metallic silver, CO₂, and the corresponding ketones. In addition, products derived from radical intermediates were detected by mass spectroscopic analysis for some silver(I) β-ketocarboxylates. Infrared and solid state ¹³C-NMR spectra of silver(I) β-ketocarboxylates suggested the presence of two types of structures involving a carbonyl group in addition to the dimeric eight-membered ring structure as in the structure of silver(I) stearate. The silver(I) β-ketocarboxylate model compound used was HCOCH₂COOAg and its structures were determined using density functional theory (DFT) and atoms-in-molecules (AIM) methods. Three types of coordinations around the Ag ion differing significantly in Ag–O bond strengths were found. Based on the calculated structures and experimental results, the relationships between the structures and decomposition temperatures are discussed in terms of the thermal decomposition process.