STANDARD MOLAR ENTHALPIES OF FORMATION AND SUBLIMATION OF SOME CRYSTALLINE BIS(8-HYDROXY-2-METHYLQUINOLINATE) METAL-COMPLEXES

The standard molar enthalpies of formation at T = 298.15 K of some cry stalline bis(8-hydroxy-2-methylquinolinate) metal complexes were deter mined from solution-reaction calorimetric measurements. 8-Hydroxy-2-me thylquinoline; or 2-methyloxine, is written as Hmeox. The values of De lta(f)H(m)(0) (M(meox)(2), cr)/(kJ.mol(-1)) are: Mg(meox)(2), -609.0 /- 4.5; Ca(meox)(2), -707.8 +/- 4.5; Sr(meox)(2), -700.0 +/- 4.8; Cu(m eox)(2), -176.6 +/- 4.4; Zn(meox)(2) -369.6 +/- 4.5; Cd(meox)(2), -298 .0 +/- 4.5; Pb(meox)(2), -239.9 +/- 4.6; Mn(meox)(2), -418.1 +/- 4.3; Co(meox)(2), -257.8 +/- 4.7; Ni(meox)(2), -243.0 +/- 6.6. Where feasib le, the standard molar enthalpies of sublimation at T = 298.15 K were determined by an effusion method. The Delta(cr)(g)H(m)(0) (M(meox)(2)) /(kJ.mol(-1)) values are: Mg(meox)(2), 224.3 +/- 6.5; Cu(meox)(2), 172 .1 +/- 3.4; Zn(meox)(2), 179.4 +/- 5.0; Cd(meox)(2), 203.3 +/- 7.3; Pb (meox)(2), 188.6 +/- 5.9; Mn(meox)(2), 211.2 +/- 7.2; Co(meox)(2), 204 .4 +/- 5.9; Ni(meox)(2), 180.9 +/- 3.7. From the standard molar enthal pies of formation in the gaseous state, the mean metal-ligand dissocia tion enthalpies were derived and compared with values for other comple xes of these metals. (C) 1998 Academic Press Limited.