ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 32, Number 3
JKCSEZ 32(3)
June 20, 1988 

Mono-oxo-bridged binuclear molybdenum(Ⅴ) complex, [Mo2O3(Phen)2(NCS)4] produces di-oxo-bridged binuclear molybdenum(Ⅴ) complex, [Mo2O4(Phen)2(NCS)2] in water + co-solvent, where the co-solvent are acetone, acetonitrile and N,N-dimethylformamide. The rate of conversion of [Mo2O3(Phen)2(NCS)4] into [Mo2O4(Phen)2(NCS)2] has been measured by spectrophotometric method. Temperature was 10℃ to 40℃ and pressure was varied up to 1500 bar. The rate constants are increased with increasing water mole fraction and decreased with increasing concentration of hydrogen ion. The order of oxygen ring formation reaction rate in various cosolvent is as follows, ACT > AN > DMF which is agreed with solvent dielectric constants. The observed negative activation entropy (ΔS≠), activation volume(ΔV≠) and activation compressibility coefficient(Δβ≠) values show that the solvent water molecule is strongly attracted to the complex at transition state. From these results, the oxygen ring formation reaction of [Mo2O3(Phen)2(NCS)4] is believed association mechanism.