Novel Air-Stable and Volatile Bis(pyridylalkenolato)palladium(II) and -platinum(II) Derivatives

Six novel homoleptic palladium(11) and platinum(II) complexes of donor-substituted alkenol ligands [PyCHC(R)OH; Py = pyridine, R = CH3, CF3, C2F5, C3F7] of the general formula M[PyCHC(R)O](2) (M = Pd, Pt) were synthesized by reacting the deprotonated ligands with PdCl2 and K2PtCl4, respectively. Molecular structures, revealed by single-crystal X-ray diffraction analyses, showed a square-planar arrangement of ligands around palladium and platinum centers, with the pyridine-ring nitrogen atoms situated in a mutually trans position. The monomeric nature of the compounds in the solution state was confirmed by multinudear (H-1, C-13, and F-19) NMR spectroscopy. Thermal decomposition profiles recorded under a nitrogen atmosphere suggested their potential as volatile precursors to palladium and platinum materials. The volatility was increased upon elongation of the perfluoroalkyl chain, which suppressed the intermolecular interactions, as is evident in crystal packings. The volatility of these compounds was attributed to bidentate chelation of the alkenol units and cooperativity among the electron-back-donating nitrogen atom and interplay of electron-withdrawing CxFy groups, resulting in an effective steric shielding of the metal atoms.