TG/DTA-based techniques for the determination of equilibrium vapour pressures of N,N - propylenebis(2,4-pentanedion-iminoato)nickel(II) for CVD applications

The Schiff’s base complexes of nickel(II) prepared by condensing 1,2-diaminopropane (pn), 1,3-diaminopropane (trien), 1,4-diaminobutane (tren) or 1,2-diaminobenzene (opdn) with 2,4-pentanedione (acac) in a 1:2 mole ratio followed by chelation with nickel(II) were examined for their volatility/decomposition behaviour for CVD applications. Among the complexes screened, only one complex namely N,N -propylenebis (2,4-pentanedioniminoato) nickel(II) (designated as [Ni(acac)2pn], Ni ) exhibited a single stepped volatilisation commencing from above its melting point (To) of 431.9 K and ending up with nil residue at about 570 K. Fast Atom Bombardment Mass Spectrometry was employed to determine the molecular mass of the vapour species to be 295 in accordance with the molecular mass for the monomeric Ni(C13H20O2N2). The equilibrium vapour pressure (pe) of Ni over the range of 434–498 K was determined to be log pe/Pa = 13.771 (±0.574)–4925.4 (±258.2) K/T by employing a TG-based transpiration technique, which yielded a value of 94.3±5.0 kJ mol−1 for its standard enthalpy of vapourisation ( Ho vap). The DTA-based melting point depression (To–T) studies were carried out on four mixtures of Ni (as a volatile solvent) with bis(2,4-pentanedionato)nickel(II) (designated as Ni(acac)2 or Ni ) as the non-volatile solute. The dependence of log XNi against 1/T(K) for the four mixtures with the solvent mole fraction XNi = 0.910, 0.897, 0.881 or 0.849 exhibited near constant slope leading to an average value of 19.4±1.6 kJ mol−1 for the standard enthalpy of fusion( Ho fus). Combining Ho vap and Ho fus, a value of 113.7 ± 6.6 kJ mol−1 for standard enthalpy of sublimation( Ho sub) was derived to facilitate the estimation of vapour pressures for solid/vapour equilibrium below the melting point. C 2006 Springer Science + Business Media, Inc