TY - JOUR
T1 - Oxidation of Hypophosphorous Acid by a Ruthenium(VI) Nitrido Complex in Aqueous Acidic Solution. Evidence for a Proton-Coupled N-Atom Transfer Mechanism
AU - Li, Ji-Rui
AU - Xu, Li-Ping
AU - Jiang, Hui-Mei
AU - Wang, Feng-Qin
AU - Xie, Jianhui
AU - Man, Wai-Lun
AU - Wang, Qian
AU - Zhuo, Shuping
AU - Lau, Tai-Chu
N1 - Funding Information:
This work was supported by Natural Science Foundation of China (21801155, 21702126) and the Research Grants Council of Hong Kong (CityU 11301618).
Publisher Copyright:
© 2022 American Chemical Society.
PY - 2022/7/11
Y1 - 2022/7/11
N2 - The oxidation of hypophosphorous acid (H3PO2) by a ruthenium(VI) nitrido complex, [(L)RuVI(N)(OH2)]+ (RuVIN; L = N,N′-bis(salicylidene)-o-cyclohexyldiamine dianion), has been studied in aqueous acidic solutions at pH 0–2.50. The reaction has the following stoichiometry: 2[(L)RuVI(N)(OH2)]+ + 3H3PO2 + H2O → 2[(L)RuIII(NH2P(OH)2)(OH2)]+ + H3PO3. The pseudo-first-order rate constant, kobs, depends linearly on [H3PO2], and the second-order rate constant k2 depends on [H+] according to the relationship k2 = k[H+]/([H+] + Ka), where k is the rate constant for the oxidation of H3PO2 molecule and Ka is the dissociation constant of H3PO2. At 298.0 K and I = 1.0 M, k = (2.04 ± 0.19) × 10–2 M–1 s–1 and Ka = (6.38 ± 0.63) × 10–2 M. A kinetic isotope effect (KIE) of 2.9 ± 0.1 was obtained when kinetic studies were carried out with D3PO2 at pH 1.16, suggesting P–H bond cleavage in the rate-determining step. On the other hand, when the kinetics were determined in D2O, an inverse KIE of 0.21 ± 0.03 (H3PO2 in H2O vs H3PO2 in D2O) was found. On the basis of experimental results and DFT calculations, the proposed mechanism involves an acid-catalyzed tautomerization of H2P(O)(OH) to HP(OH)2; the latter molecule is the reacting species which reacts with RuVIN via a proton-coupled N-atom transfer pathway.
AB - The oxidation of hypophosphorous acid (H3PO2) by a ruthenium(VI) nitrido complex, [(L)RuVI(N)(OH2)]+ (RuVIN; L = N,N′-bis(salicylidene)-o-cyclohexyldiamine dianion), has been studied in aqueous acidic solutions at pH 0–2.50. The reaction has the following stoichiometry: 2[(L)RuVI(N)(OH2)]+ + 3H3PO2 + H2O → 2[(L)RuIII(NH2P(OH)2)(OH2)]+ + H3PO3. The pseudo-first-order rate constant, kobs, depends linearly on [H3PO2], and the second-order rate constant k2 depends on [H+] according to the relationship k2 = k[H+]/([H+] + Ka), where k is the rate constant for the oxidation of H3PO2 molecule and Ka is the dissociation constant of H3PO2. At 298.0 K and I = 1.0 M, k = (2.04 ± 0.19) × 10–2 M–1 s–1 and Ka = (6.38 ± 0.63) × 10–2 M. A kinetic isotope effect (KIE) of 2.9 ± 0.1 was obtained when kinetic studies were carried out with D3PO2 at pH 1.16, suggesting P–H bond cleavage in the rate-determining step. On the other hand, when the kinetics were determined in D2O, an inverse KIE of 0.21 ± 0.03 (H3PO2 in H2O vs H3PO2 in D2O) was found. On the basis of experimental results and DFT calculations, the proposed mechanism involves an acid-catalyzed tautomerization of H2P(O)(OH) to HP(OH)2; the latter molecule is the reacting species which reacts with RuVIN via a proton-coupled N-atom transfer pathway.
UR - http://www.scopus.com/inward/record.url?scp=85134426463&partnerID=8YFLogxK
U2 - 10.1021/acs.inorgchem.2c01627
DO - 10.1021/acs.inorgchem.2c01627
M3 - Article
VL - 61
SP - 10567
EP - 10574
JO - Inorganic Chemistry
JF - Inorganic Chemistry
SN - 0020-1669
IS - 27
ER -