Palladium(II) and Platinum(II) Complexes Bearing ONS-Type Pincer Ligands: Synthesis, Characterization and Catalytic Investigations.

This work describes the synthesis of eight new Pd(II) and Pt(II) complexes with the general formula [M(TSC)Cl], where TSC represents the 4N-monosubstituted thiosemicarbazone derived from 2-acetylpyridine N-oxide with the substituents CH 3 (H4MLO), C 2 H 5 (H4ELO), phenyl (H4PLO) and (CH 3 ) 2 (H4DMLO). These complexes have been characterized by elemental analysis, molar conductivity, IR spectroscopy, 1 H, 13 C, 195 Pt and ESI-MS. The complexes exhibit a square planar geometry around the metallic center coordinated by a thiosemicarbazone molecule acting as a donor ONS-type pincer ligand and by a chloride, as confirmed by the molecular structures of the complexes, [Pd(4ELO)Cl] ( 3 ) and [Pd(4PLO)Cl] ( 5 ), determined by single-crystal X-ray diffraction. The 195 Pt NMR spectra of the complexes of formulae [Pt(4PLO)Cl] ( 6 ) and [Pt(4DMLO)Cl] ( 8 ) in DMSO show a single signal at -2420.4 ppm, confirming the absence of solvolysis products. Complexes 3 and 5 have been tested as catalysts in the Suzuki-Miyaura cross-coupling reactions of aryl bromides with phenylboronic acid, with yields of between 50 and 90.