Mechanochemical Sustainable Synthesis of Platinum(II) Complexes: Reactivity Inversion and Coordination Mode Control

Abstract

Mechanochemistry is emerging as a sustainable alternative to conventional solution-based synthesis, yet its application to platinum(II) coordination chemistry remains limited. Herein, we report a systematic investigation of the mechanochemical synthesis of Pt(II) complexes bearing S-, N-, P-donor, and diene ligands. Under solvent-free ball-milling conditions, a broad range of structurally diverse complexes was efficiently prepared from commercially available precursors, often reaching quantitative conversion within minutes and requiring minimal workup. A key finding is the reversal of precursor reactivity relative to solution-phase chemistry, with PtCl2 consistently outperforming K2[PtCl4] under mechanochemical conditions. This behavior highlights the dominant influence of solid-state effects, where local mixing and metal–ligand bond activation govern reactivity rather than solubility and ligand-exchange kinetics. Mechanochemical conditions also led to atypical coordination outcomes, including the formation of κ2-terpyridine complexes instead of the expected κ3 species. Comparison with conventional synthetic methods revealed significantly improved green metrics, including lower E-factors, EMY, and reduced solvent consumption. Preliminary catalytic studies demonstrate the potential of selected Pt(II) complexes in mechanochemically assisted oxidation reactions. Overall, this work establishes mechanochemistry as an efficient and versatile complementary approach to Pt(II) complex synthesis and provides new insights into solid-state reactivity and coordination behavior.