Three new O,N-coordinated Ni(II) complexes: Syntheses, crystal structures, and MOCVD applications

Abstract

Three new O,N-coordinated nickel (II) complexes, namely, Ni(dmpda(acac)2) (1), Ni(pda)(acac)2 (2) and Ni(pda)(tfac)2 (3) have been synthesized ((dmpda(acac)2 – N,N′-(2,2-dimethyl-1,3-diaminopropane)-bis-(2,4-pentanedioniminoato(2-), acac – 2,4-pentanedionato(−), pda – 1,3-diaminopropane, tfac – 1,1,1-trifluoroacetylacetonato(−)) and tested as new precursors for metal–organic chemical vapor deposition (MOCVD). The structures of 1–3 were determined by single-crystal X-ray diffraction (XRD) and further characterized by IR and Raman spectroscopies. All three compounds crystallize in the triclinic space group P1¯ with unit cell parameters of a = 9.0294(6), b = 9.2879(6), c = 10.4065(6) Å, α = 74.855(3), β = 68.717(3), γ = 78.708(3) for 1; a = 7.6947(2), b = 10.3087(3), c = 10.7144(3) Å, α = 101.784(1), β = 95.367 (1), γ = 106.134(1) for 2; and a = 7.8931(5), b = 10.8803(8), c = 10.9438(7) Å, α = 103.283(2), β = 97.070(3), γ = 103.050(2) for 3. The density functional theory (B3LYP) quantum chemical calculations have been used for detailed assignment of all intense bands in the vibrational spectra of the compounds studied. Thermal gravimetric analysis (TG/DTA) has shown that the species 1 and 3 sublime almost without decomposition, and 2 decomposes to some extent. MOCVD test experiments were carried out at low pressure (10 Torr) using 1 and 3 as precursors on Ta/Si substrates. The films have been characterized by X-ray powder diffraction, scanning electron microscopy, and energy dispersive spectroscopy were found to be primarily composed either of fcc-Ni or Ni3C phases. The phase composition of the films strongly depends on the MOCVD conditions.