Mechanochemical Access to Pd(II) and Pt(II) Square-Planar Complexes

Mechanochemistry is aligned with green chemistry, involves chemical reactions driven by mechanical forces. Organometallic mechanochemistry remains relatively underexplored and only recently key organometallic complexes have been synthesized via this method. Although Pd(II) and Pt(II) complexes are widely utilized in catalysis and medicinal chemistry, their preparation under mechanochemical conditions have been poorly investigated. In the present study, several square planar Pd(II) and Pt(II) complexes were obtained mechanochemically from commercial halogenated and halogen-like precursors and commercial ligands. The synthesized complexes have the following structures: [M(COD)X2] with 1,5-cyclooctadiene; [M(DMSO)X2] with dimethyl sulfoxide; [M(N⌒N)X2] with bidentate N-ligands; and [M(P)2X2] and [M(P⌒P)X2] featuring mono- and bidentate P-ligands. Synthesis reactions never exceed two hours of milling and they proceed with high to quantitative yields and excellent product purity, supported by favourable green chemistry metrics. In addition to the synthesis and characterization of the complexes, studies were carried out to understand the isomeric composition of the obtained products (if possible), and how milling time affects these reactions.