Unveiling the role of CO2 in the spontaneous formation of a platinum(ii)–amino acid complex

Abstract

The reaction between the designed benzoxadiazole-functionalized diamine ligand BOSA(NH₂)₂ and Pt(DMSO)₂Cl₂ under ambient atmosphere exclusively yields the carbamic acid–platinum complex BOSA(NH₂)(NHCOOH)PtCl₂, with no experimental evidence for the formation of the non-carboxylated analogue BOSA(NH₂)₂PtCl₂. High-resolution mass spectrometry (HR-MS) confirms the rapid in situ generation of the carboxylated ligand BOSA(NH₂)(NHCOOH) in solution. Density functional theory (DFT) calculations elucidate that CO₂ activation proceeds via either an intramolecular or a solvent-mediated pathway. This study demonstrates that pre-association of CO₂ with the diamine ligand can be the decisive factor in platinum complex synthesis, directly leading to amino acid-based platinum complexes like BOSA(NH₂)(NHCOOH)PtCl₂.