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Journal of the Korean Chemical Society (JKCS)

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

Oxygen Ring Formation Reaction of Mono-Oxo-Bridged Binuclear Molybdenum(Ⅴ) Complex (Ⅱ). Reaction of [Mo2O3(Phen)2(NCS)4] with Solvent Water in Water + Co-Solvent Mixtures

한개의 산소다리를 가진 몰리브덴(Ⅴ) 착물의 산소고리화 반응 (Ⅱ). 2성분 혼합용매에서 용매물과 [Mo2O3(Phen)2(NCS)4]의 반응
Sang-Oh Oh, Huee-Young Seok

오상오, 석휘영
물-아세톤, 물-아세토니트릴 및 물-디메틸포름아미드의 2성분 혼합용매중에서 한개의 산소다리로 된 이핵몰리브텐(Ⅴ)착물, [Mo2O3(Phen)2(NCS)4]은 두개의 산소다리로 된 이핵 몰리브텐(Ⅴ)착물, [Mo2O4(Phen)2(NCS)2]을 생성한다. [Mo2O3(Phen)2(NCS)4]가 [Mo2O4(Phen)2(NCS)2]로 바뀌는 속도는 분광광도법으로 측정하였다. 이 때 온도는 10℃에서 40℃, 압력은 1bar에서 1500bar로 변화시켰다. 속도상수는 물의 농도 증가에 따라 증가하였다. 수소이온농도의 증가에 따라서는 감소하였다. 여러가지 공용매에서 산소고리화 반응속도는 유전상수(ε/εo)의 증가와 같이 ACT < AN < DMF의 순으로 증가하였다. 관찰된 음의 활성화엔트로피(ΔS≠), 활성화부피(ΔV≠) 및 활성화 압축율(Δβ≠) 값은 착물이 전이상태에서 용매 물분자를 강하게 당기는 회합성메카니즘임을 알게 한다.

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.

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