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

Six novel homoleptic palladium­(II) 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 multinuclear
(1H, 13C, and 19F) 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.