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Oxidation of Hypophosphorous Acid by a Ruthenium(VI) Nitrido Complex in Aqueous Acidic Solution. Evidence for a Proton-Coupled N-Atom Transfer Mechanism
Inorganic Chemistry ( IF 4.6 ) Pub Date : 2022-06-24 , DOI: 10.1021/acs.inorgchem.2c01627
Ji-Rui Li 1 , Li-Ping Xu 1 , Hui-Mei Jiang 1 , Feng-Qin Wang 1 , Jianhui Xie 2 , Wai-Lun Man 3 , Qian Wang 1 , Shuping Zhuo 1 , Tai-Chu Lau 4
Affiliation  

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.

中文翻译:

在酸性水溶液中通过氮化钌 (VI) 络合物氧化次磷酸。质子耦合 N 原子转移机制的证据

次磷酸 (H 3 PO 2 ) 被氮化钌 (VI) 络合物 [(L)Ru VI (N)(OH 2 )] + ( Ru VI N ; L = N , N '-bis(salicylidene ) 氧化)- o -cyclohexyldiamine dianion),已在 pH 0–2.50 的酸性水溶液中进行了研究。该反应具有以下化学计量: 2[(L)Ru VI (N)(OH 2 )] + + 3H 3 PO 2 + H 2 O → 2[(L)Ru III (NH 2 P(OH) 2 )(哦2)] + + H 3 PO 3。根据关系k 2 = k [H + ]/ ,伪一级速率常数k obs线性依赖于 [H 3 PO 2 ],二级速率常数k 2依赖于 [H + ]/ ([H + ] + K a ),其中k是 H 3 PO 2分子氧化的速率常数,K a是 H 3 PO的解离常数2 . 在 298.0 K 和I = 1.0 M 时,k = (2.04 ± 0.19) × 10 –2 M –1 s –1和Ka = (6.38 ± 0.63) × 10 –2 M。动力学同位素效应 (KIE) 为2.9当在 pH 1.16 下用 D 3 PO 2进行动力学研究时获得 ± 0.1 ,这表明在速率决定步骤中 P-H 键断裂。另一方面,当在 D 2 O 中测定动力学时,逆 KIE 为 0.21 ± 0.03(H 2 O 中的H 3 PO 2D 2中的 H 3 PO 2O) 被发现。基于实验结果和 DFT 计算,所提出的机理涉及 H 2 P(O)(OH) 到 HP(OH) 2的酸催化互变异构化;后一种分子是通过质子耦合的 N 原子转移途径与Ru VI N反应的反应物质。
更新日期:2022-06-24
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