Characterization, kinetics and mechanism of thermal decomposition of photosubstituted ethylenediamine complexes of molybdate(IV) and tungstate(IV) with chromium(III)

• Published in: Thermochimica acta Vol. 317; no. 2; pp. 183 - 192
• Main Authors: Ali, S.I., Majid, Kowsar
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 09.07.1998; Elsevier Science
• Subjects: Chemistry; Coordination compounds; Cr(III) complexes; Exact sciences and technology; General and physical chemistry; Inorganic chemistry and origins of life; Octacyanomolybdate (IV); Octacyanotungstate (IV); Photochemistry; Physical chemistry of induced reactions (with radiations, particles and ultrasonics); Preparations and properties; Thermal decomposition; Thermal kinetics; Cr(III) complexes; Octacyanotungstate (IV); Octacyanomolybdate (IV); Thermal decomposition; Thermal kinetics; Organic ligand; Transition metal Complexes; Photochemical reaction; Cyano complex; Oxo complex; Molybdenum IV Complexes; Ultraviolet radiation; Hydroxo complex; Tungsten IV Complexes; Chromium III Complexes; Complexes Mixed; Heteronuclear complex; Dinuclear complex; Thermal analysis; Kinetic parameter; Chemical synthesis; Activation energy; Hydrates
• ISSN: 0040-6031; 1872-762X
• DOI: 10.1016/S0040-6031(98)00379-7

Photoinitiated substitution complexes of [M(CN) 8] 4− (where M= Mo(IV) or W(IV)) and ethylenediamine with chromium(III) have been synthesized and characterized. On the basis of elemental analysis, the complexes have been assigned formulas as folows: Cr[Mo(CN)(C 2H 8N 2)(OH) 6]·2H 2O I for Mo(IV); and Cr[W(C 2H 8N 2)(O 2)(OH) 3]·H 2O II for W(IV) The characteristic IR absorption peaks for different entities present support the assigned formulas. Complex I shows the absorption peaks due to ν(CN) stretching bond, NH asymmetric deformation, NH symmetric deformation and NH 3 rocking mode showing the presence of cyanide and ethylenediamine. The loss of the absorption peak due to ν(CN) stretching in the spectra of complex II confirms the substitution of all the cyanide ligands. The thermal degradation of the complexes has been studied by TG and DSC techniques. Both the complexes have a similar thermal decomposition behavior: involving expulsion of water molecules in the first step followed by the expulsion of other ligands. Kinetics and a thermal decomposition mechanism have been proposed for each complex. Thermodynamic parameters such as activation energy ( E a), pre-exponential factor ( A) and entropy of activation (Δ S #) have been calculated for each step, employing different integral methods of Doyle, Coats and Redfern, and Arrhenius. The reaction enthalpy is obtained from DSC data