Compounds with Chelating 3-Dimethylamino-1-propyl Ligands as Chemical Vapor Deposition Precursors. Synthesis and Characterization of M[(CH2)3NMe2]2 Complexes of Nickel(II), Palladium(II), and Platinum(II)

Abstract

We describe the synthesis and characterization of three new square-planar compounds of stoichiometry M[(CH₂)₃NMe₂]₂, where M = Ni, Pd, or Pt, each of which contains two chelating 3-dimethylamino-1-propyl ligands. The nickel(II) and palladium(II) compounds decompose above −78 and 0 °C, respectively, but the platinum(II) compound has a thermolysis onset temperature of 130 °C. The Pd and Pt complexes are dynamic in solution: they undergo ring inversion with small free energies of activation of ΔG^⧧ = 7.9 ± 0.1 and 8.3 ± 0.1 kcal mol^–1, respectively, at 298 K. The Pt complex sublimes at 40 °C and 5 mTorr. In benzene solution, the Pt compound thermolyzes primarily through β-hydrogen elimination; 80 ± 10% of the hydrogen atoms and 75 ± 5% of the carbon atoms from the precursor can be accounted for in the byproducts. The thermolysis of the Pt complex in C₆D₆ follows first-order kinetics, with an activation free energy ΔG^⧧ of 29.9 ± 0.1 kcal mol^–1 at 110 °C. Under CVD conditions, thin films grown of the Pt complex at 200 °C contain nanocrystalline Pt; analysis of the film growth byproducts suggest that the main decomposition pathway involves β-hydrogen elimination and reductive elimination steps, as seen in solution.