Thermochemistry of the ternary complex Nd(Et_ndtc)₃(phen)

The ternary solid complex has been synthesized with sodium diethyldithiocarbamate (NaEt₂dtc·3H₂O), 1,10-phenanthroline (o-phen·H₂O) and hydrated neodymium chloride in absolute ethanol. The title complex was identified as the general formula of Nd(Et₂dtc)₃(phen) by chemical and elemental analyses. IR spectrum of the complex showed that the Nd³⁺ coordinated with six sulfur atoms of three NaEt₂dtc and two nitrogen atoms of o-phen. It was assumed that the coordination number of Nd³⁺ is eight. The enthalpy change of liquid-phase reaction of formation, Δ_rH (1), was determined as (-12.274±0.050) kJ·mol⁻¹ at 298.15 K by a microcalorimeter, the enthalpy change of the solid-phase reaction of formation, Δ_rH (s), was calculated as (149.069±0.314) kJ·mol⁻¹ on the basis of a thermochemical cycle. The thermodynamics of reaction of formation was studied by changing the temperature of liquid-phase reaction. The constant-volume combustion energy of the complex, Δ_cU, was determined as (-18674.22±8.33) kI·mol⁻¹ by a precise rotating-bomb calorimeter at 298.15 K. Its standard enthalpy of combustion, Δ_cH, and standard enthalpy of formation, Δ_fH, were calculated as (-18693.43 ± 8.33) kJ·mol⁻¹ and (-47.03 ± 9.17) kJ·mol⁻¹, respectively.