Kinetics and mechanisms of the oxidation of hypophosphite and phosphite with trans-[RuVI(L)(O)2]2+ (L = 1,12-dimethyl-3,4 : 9,10-dibenzo-1,12-diaza-5,8-dioxacyclopentadecane)

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)22_Publication in policy or professional journal

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Original languageEnglish
Pages (from-to)17-20
Journal / PublicationJournal of the Chemical Society, Dalton Transactions
Issue number1
Publication statusPublished - 2000

Abstract

The kinetics of the oxidation of hypophosphite and phosphite by trans-[Ru(L)(O)2]2+ (L = 1,12-dimethyl-3,4:9,10-dibenzo-1,12-diaza-5,8-dioxacyclopentadecane) have been studied in aqueous acidic solutions. The reactions have the following stoichiometry (x = 2 or 3): trans-[RuVI(L)(O)2]2+ + H2POx - + H2O → trans-[RuIV(L)(O)(OH2)]2+ + H2POx+1 -,. The two reactions have the same rate law (P = hypophosphite or phosphite): -d[RuVI]/dt = k/(1 + [H+]/K)[RuVI][P]. For hypophosphite, k = (1.3 ± 0.1).dm3 mol-1 s-1 and K= (9.7 ± 0.5) × 10-2 mol dm-3 at 298 K and I= 1.0 mol dm-3. For phosphite, k = (4.8 ± 0.4) × 10-2 dm3 mol-1 s-1 and K= (1.2 ± 0.2) × 10-2 mol dm-3 at 298 K and I = 0.2 mol dm-3. The effects of temperature were studied from 15°C to 40°C. For hypophosphite, ΔH = (60 ± 2) kJ mol-1 and ΔS = (-41 ± 4) J mol-1 K-1 at pH = 1.86 and I = 1.0 mol dm-3. For phosphite, ΔH = (59 ± 4) kJ mol-1 and ΔS = (-75 ± 13) J K-1 mol-1 at pH = 2.3 and I = 0.2 mol dm-3. Deuterium isotope effects have also been investigated. For hypophosphite, the kinetic isotope effect, k(H2PO2 -)/k(D2PO2 -) is 4.1 at pH = 1.07 and I = 1.0 mol dm-3. For phosphite, the kinetic isotopic effect, k(HDPO3 -)/k(D2PO3 -), is 4.0 at pH = 2.30 at I = 0.2 mol dm-3. A mechanism involving hydride transfer from P-H to Ru=O is proposed for these two reactions. © The Royal Society of Chemistry 2000.

Citation Format(s)

Kinetics and mechanisms of the oxidation of hypophosphite and phosphite with trans-[RuVI(L)(O)2]2+ (L = 1,12-dimethyl-3,4 : 9,10-dibenzo-1,12-diaza-5,8-dioxacyclopentadecane). / Yiu, Douglas T. Y.; Chow, Kwok-Ho; Lau, Tai-Chu.

In: Journal of the Chemical Society, Dalton Transactions, No. 1, 2000, p. 17-20.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)22_Publication in policy or professional journal