Thermochemistry On The Complexes Of Hydrated Ianthanide Chloride With Diethylammonium Diethyldithiocarbamate

Thermochemistry on the complexes of hydrated lanthanide chloride with diethylammonium diethyldithiocarbamateThe complexes of hydrated lanthanide chloride with diethylammonium diethyldithiocarbamate (D-DDC) were synthesized in absolute alcohol and their thermochemical characteristics were discussed in this paper. A new monocrystalline of Et2NH2[Nd(S2CNEt2)4] was prepared as well.13 complexes were identified as Et2NH2[Ln(S2CNEt2)4](Ln = La, Pr, Nd, Sm~Lu) by chemical and elemental analyses.From the monocrystal structure of Et2NH2[Nd(S2CNEt2)4], the crystal system of the complex was determined as monoclinic system , space group P2(l)/n, a = 1.37517 (14) nm, b= 2.1146(2)nm,c= 1.44641(15) nm, a= 90.000, B= 102.028(2), Y= 90.000, V= 4.1137(7) nm3, Z= 4, F(000)= 1760, Mr=852.45, Dc= 4.1376 g.cm-3, u= 1.694 mm.Its geometry showed that Nd3+ was coordinated with eight sulfur atoms from four ligands. The coordination polyhedron can be described as a distorted dodecahedron. It can be presumed that the structures of other complexes were similar to that of Et2NH2[Nd(S2CNEt2)4] by IR, UV and X-ray power diffraction .The decompositions of the complexes were studied by TG-DTG and DSC techniques. The results showed that the complexes were more stable than ligand. The decomposition mechanisms of the complexes of Et2NH2[Ln(S2CNEt2) 4] ( Ln = La, Pr, Nd ) were speculated from these curves: at the first stage, a small amount of complexes were dissociated; then the final products of rare earth sulfide were obtained by completely decomposed. The first stage decomposition processes of these complexes were calculated by non-isothermal kinetics methods, and the probable mechanisms were 13, 5, 15 functions, respectively. The apparent activation energy(E/ kJ.mol-1) and pre-exponential constant (A) were: La: 88.31, 5.33×107; Pr: 97.55, 2.69×108; Nd: 107.33, 5.24×109. The kinetics equations of these processes were: (1)Et2NH2[La(S2CNEt2)4]: da/dT=(1.0669×108/β).exp(-88.31×103/RT).(1-a)]1/2[-ln( 1 - a)]1/2 =(5.3345×107/βJ0Texp(-88.31 ×103/RT)dT (2)Et2NH2[Pr(S2CNEt2)4]: da/dT=( 1.6131×109/p) exp(-97.55×103/RT)-( 1 - a )[1 -(1 - a )1/3]1/2[1-(1- a )1/3]1/2 = (2.688×108/β) 0Texp(-97.55×103/RT)dT (3)Et2NH2[Nd(S2CNEt2)4]: da/dT>(6.9845×109/β).exp(-107.33×103/RT).(1-a)[-ln(1-a)]1/4[-ln(1-a)]1/4=(5.2384×109/β) 0Texp(-107.33×103/RT)dTThe constant volume combustion energies, cU , of the complexes were determined by an RBC- II precise rotating-bomb calorimeter, the standard molar enthalpies of combustion, cH and standard molar enthalpies of formation, fHm were calculated, respectively. The results are (kJ.mol-1) :cU:-19490.07 ±8.23 (La); - 19391.14 ± 10.72 (Pr); - 19208.32 ± 8.99 (Nd); -18439.79±7.77 (Sm); - 17130.37± 8.92 (Eu); - 18081.35±9.04 (Gd);- 18629.26 ± 9.00 (Tb); - 18945.52± 10.56 (Dy); - 17022.86 ± 8.67 (Ho); -18344.93± 8.95 (Er); - 18674.59± 9.11 (Tm); - 18896.14± 10.07 (Yb); -19079.22± 8.59 (Lu).cHm: -19517.96 ±8.23 (La); - 19419.03 ±10.72 (Pr); - 19236.21 ± 8.99 (Nd); -18467.68 ± 7.77 (Sm): - 17158.26± 8.92 (Eu); - 18109.24 ± 9.04 (Gd);- 18656.15 ±9.00 (Tb); -18973.41± 10.56 (Dy); - 17050.75± 8.67 (Ho) -18372.82 ±8.95 (Er); - 18702.48 ± 9.11 (Tm); - 18924.03 ± 10.07 (Yb); -19107.12 ± 8.59 (Lu).fHm: -628.91 ±8.88 (La); - 742.97 ± 11.71 (Pr); -918.15±9.59 (Nd);-1690.32±8.50(Sm); - 2923.54±9.55 (Eu); - 2048.86±9.79 (Gd);-1507.95±9.64(Tb); - 1209.58 ±11.24 (Dy); -3140.01 ± 9.59 (Ho)-1826.39±9.59(Er); - 1492.15 ±10.13 (Tm); - 1233.53 ±10.66 (Yb);-1090.44±9.95(Lu).The specific heat capacities, c(Jmol-1K-1), of 13 complexes were determined by a RD496-III microcalorimeter. The results were : 109.932 ±1.102(La); 94.949±0.511 (Pr); 92.416±2.026 (Nd); 71.979±0.891 (Sm); 62.178±1.919 (Eu); 69.112±1.907(Gd); 73.957±2.183 (Tb); 78.434±1.605 (Dy); 65.409±2.912 (Ho); 79.626±1.568 (Er); 86.234±2.685 (Tm); 92.665±1.121 (Yb); 98.856±0.651 (Lu). In addition, the enthalpies change of liquid-phase were determined and those of solid-phase reaction of for...