VAPOR-PRESSURES, ENTHALPIES OF VAPORIZATION, AND THERMAL-BEHAVIOR OF THE BIS(1,1,1,5,5,5-HEXAFLUOROPENTANE-2,4-DIONATO)BARIUM-CENTER-DOT(POLYETHER) COMPLEXES - BA(CF3COCHCOCF3)(2)CENTER-DOT(CH3O(CH2CH2O)(4)CH3) AND BA(CF3COCHCOCF3)(2)CENTER-DOT(C-(CH2CH2O)(6))

Static vapour pressures are reported for the barium beta-diketonate polyether adducts Ba(hfac)(2) .(tetraglyme) and Ba(hfac)(2) .(18-crown-6), which are important as precursors in chemical vapour deposition (hfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dionato (CF3COCHCOCCF3)(-), tetraglyme = 2,5,8,11,14-pentaoxapentadecane, CH3O(CH2CH2O)(4)CH3, 18-crown-6 = 1,4,7,10,13,16-hexaoxacyclooctadecane, c-(CH2CH2O)(6)). The thermal behaviour of the compounds was also investigated by d.s.c., elemental analysis, and visual observations. Under moderately fast heating, Ba(hfac)2 .(tetraglyme) melts without significant decomposition at the temperature T approximate to 428 K. However, the compound may melt during prolonged heating at considerably lower temperatures because of the formation of trace impurities. The molar enthalpy of fusion was measured as (34.8 +/- 0.5) kJ . mol(-1). Vapour pressures for molten Ba(hfac)(2) .(tetraglyme) in the temperature range 401 K to 447 K were fitted to the equation: Ig(p/Pa) = 13.69 - 5318(T/K)(-1), consistent with a value of (101.8 +/- 1.2) kJ . mol(-1) for the average molar enthalpy of vaporisation. Ba(hfac)(2) .(1 8-crown-6) samples melted with decomposition only at T > approximate to 533 K. This compound undergoes a solid-state phase transition, study of which is complicated by slow kinetics. Conversion of the low-temperature form to the high temperature form was demonstrated at temperatures as low as 423 K, and is accompanied by a molar enthalpy change of (16.7 +/- 0.3) kJ . mol(-1). Vapour pressures for solid Ba(hfac)(2) .(18-crown-6) in the temperature range 412 K to 468 K were fitted to the equation: Ig(p/Pa) = 12.82 - 5480(T/K)(-1), consistent with a value of (104.9 +/- 1.3) kJ . mol(-1) for the average molar enthalpy of sublimation. (C) 1995 Academic Press Limited