A solid complex, Er(C5H8NS2)(3)(C12H8N2), has been obtained from the reaction of hydrous erbium chloride, ammonium pyrrolidinedithiocarbamate (APDC), and 1,10-phenanthroline (o-phen-H2O) in absolute ethanol. The enthalpy change of the reaction of complex formation from a solution of the reagents, Delta(r) H-m(theta)(sol), and the molar heat capacity of the complex, c., were determined at 298.15 K by using an RD-496 111 heat conduction microcalorimeter. The enthalpy change of complex formation from the reaction of reagents in the solid phase, Delta(r)H(m)(theta) (s), was calculated on the basis of an appropriate thermochemical cycle and other auxiliary thermodynamic data. The thermodynamics of the reaction of formation of the complex was investigated via the reaction in solution. Fundamental parameters such as the activation enthalpy, the activation entropy, the activation free energy, the apparent reaction rate constant, the apparent activation energy, the preexponential constant, and the reaction order were obtained by combining the thermochemical data of the reaction and kinetic equations with the data of thermokinetic experiments. The constant-volume combustion energy of the complex, A,U, was determined by an RBCII-type rotating-bomb calorimeter at 298.15 K. Its standard enthalpy of combustion, Delta(c)H(m)(theta), and standard enthalpy of formation, Delta(f)H(m)(theta), were calculated.