Oxidation of Hypophosphorous Acid by a Ruthenium(VI) Nitrido Complex in Aqueous Acidic Solution. Evidence for a Proton-Coupled N-Atom Transfer Mechanism

Ji Rui Li; Li Ping Xu; Hui Mei Jiang; Feng Qin Wang; Jianhui Xie; Wai Lun Man; Qian Wang; Shuping Zhuo; Tai Chu Lau

doi:10.1021/acs.inorgchem.2c01627

Oxidation of Hypophosphorous Acid by a Ruthenium(VI) Nitrido Complex in Aqueous Acidic Solution. Evidence for a Proton-Coupled N-Atom Transfer Mechanism

Ji Rui Li, Li Ping Xu, Hui Mei Jiang, Feng Qin Wang, Jianhui Xie, Wai Lun Man, Qian Wang^*, Shuping Zhuo^*, Tai Chu Lau^*

^*Corresponding author for this work

Department of Chemistry

Research output: Contribution to journal › Journal article › peer-review

Abstract

The oxidation of hypophosphorous acid (H₃PO₂) by a ruthenium(VI) nitrido complex, [(L)Ru^VI(N)(OH₂)]+ (Ru^VIN; 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)Ru^VI(N)(OH₂)]⁺ + 3H₃PO₂ + H₂O → 2[(L)Ru^III(NH₂P(OH)₂)(OH₂)]+ + H₃PO₃. The pseudo-first-order rate constant, k_obs, 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 K_a 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 K_a = (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 Ru^VIN via a proton-coupled N-atom transfer pathway.

Original language	English
Pages (from-to)	10567–10574
Number of pages	8
Journal	Inorganic Chemistry
Volume	61
Issue number	27
Early online date	24 Jun 2022
DOIs	https://doi.org/10.1021/acs.inorgchem.2c01627
Publication status	Published - 11 Jul 2022

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Inorganic Chemistry
Physical and Theoretical Chemistry

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@article{ebef4cac082a4eceb16aa6049d510039,

title = "Oxidation of Hypophosphorous Acid by a Ruthenium(VI) Nitrido Complex in Aqueous Acidic Solution. Evidence for a Proton-Coupled N-Atom Transfer Mechanism",

abstract = "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.",

author = "Li, {Ji Rui} and Xu, {Li Ping} and Jiang, {Hui Mei} and Wang, {Feng Qin} and Jianhui Xie and Man, {Wai Lun} and Qian Wang and Shuping Zhuo and Lau, {Tai Chu}",

note = "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: {\textcopyright} 2022 American Chemical Society.",

year = "2022",

month = jul,

day = "11",

doi = "10.1021/acs.inorgchem.2c01627",

language = "English",

volume = "61",

pages = "10567–10574",

journal = "Inorganic Chemistry",

issn = "0020-1669",

publisher = "American Chemical Society",

number = "27",

}

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.

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U2 - 10.1021/acs.inorgchem.2c01627

DO - 10.1021/acs.inorgchem.2c01627

M3 - Journal article

SN - 0020-1669

VL - 61

SP - 10567

EP - 10574

JO - Inorganic Chemistry

JF - Inorganic Chemistry

IS - 27

ER -

Oxidation of Hypophosphorous Acid by a Ruthenium(VI) Nitrido Complex in Aqueous Acidic Solution. Evidence for a Proton-Coupled N-Atom Transfer Mechanism

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