New Insights into Mechanism of Molybdenum(VI)–Dioxo Complex Catalyzed Hydrosilylation of Carbonyls: An Alternative Model for Activating Si–H Bond

Recently, a series of oxo/nitrido-Re^V/Mo^VI/Ru^VI/Mn^V complexes were demonstrated to be efficient catalysts in activating silanes and catalyzing hydrosilylations of unsaturated organic substrates. In the present study, the high-valent molybdenum­(VI)–dioxo complex MoO₂Cl₂ catalyzed hydrosilylations of carbonyls was reinvestigated using density functional theory method. Previous experimental and theoretical investigations suggested a [2 + 2] addition pathway for MoO₂Cl₂ catalyzed hydrosilylations of ketones. In the present study, we propose an ionic outer-sphere mechanistic pathway to be the most favorable pathway. The key step in the ionic outer-sphere pathway is oxygen atom of CO bonds nucleophilically attacking the silicon atom in an η¹-silane molybdenum adduct. The Si–H bond is then cleaved heterolytically. This process features a novel S_N2@Si transition state, which then generates a loosely bound ion pair: anionic molybdenum hydride paired with silylcarbenium ion ([MoO₂Cl₂H]⁻ [SiR₃(OCR′R″)]⁺) in solvent. The last step is silylcarbenium ion abstracting the hydride on molybdenum hydride to yield silyl ether. The calculated activation free energy barrier of the rate-determing step was 24.1 kcal/mol for diphenylketone (PhCOPh) and silane of PhMe₂SiH. Furthermore, the ionic outer-sphere pathway is calculated to be ∼10.0 kcal/mol lower than the previously proposed [2 + 2] addition pathway for a variety of silanes and aldehyde/ketone substrates. This preference arises from stronger electrophilicity of the high-valent molybdenum­(VI) metal center toward a hydride. Here, we emphasize MoO₂Cl₂ behaves similar to Lewis acidic trispentafluorophenyl borane B­(C₆F₅)₃ in activating Si–H bond

New Insights into Hydrosilylation of Unsaturated Carbon–Heteroatom (CO, CN) Bonds by Rhenium(V)–Dioxo Complexes

The hydrosilylation of unsaturated carbon–heteroatom (CO, CN) bonds catalyzed by high-valent rhenium­(V)–dioxo complex ReO₂I­(PPh₃)₂ (<b>1</b>) were studied computationally to determine the underlying mechanism. Our calculations revealed that the ionic outer-sphere pathway in which the organic substrate attacks the Si center in an η¹-silane rhenium adduct to prompt the heterolytic cleavage of the Si–H bond is the most energetically favorable process for rhenium­(V)–dioxo complex <b>1</b> catalyzed hydrosilylation of imines. The activation energy of the turnover-limiting step was calculated to be 22.8 kcal/mol with phenylmethanimine. This value is energetically more favorable than the [2 + 2] addition pathway by as much as 10.0 kcal/mol. Moreover, the ionic outer-sphere pathway competes with the [2 + 2] addition mechanism for rhenium­(V)–dioxo complex <b>1</b> catalyzing the hydrosilylation of carbonyl compounds. Furthermore, the electron-donating group on the organic substrates would induce a better activity favoring the ionic outer-sphere mechanistic pathway. These findings highlight the unique features of high-valent transition-metal complexes as Lewis acids in activating the Si–H bond and catalyzing the reduction reactions

Mechanistic Investigation Into Catalytic Hydrosilylation with a High-Valent Ruthenium(VI)–Nitrido Complex: A DFT Study

Density functional theory calculations with the B3LYP-D function have been performed to investigate the mechanism of carbonyl hydrosilylation reactions catalyzed by the high-valent nitridoruthenium­(VI) complex [RuN­(saldach)­(CH₃OH)]⁺[ClO₄]⁻ (<b>1</b>; saldach is the dianion of racemic <i>N</i>,<i>N</i>′-cyclohexanediylbis­(salicylideneimine)). Our computational results indicate a favored ionic outer-sphere mechanistic pathway. This pathway initiates with a silane addition to the Ru^VI center, which proceeds through a S_N2-Si transition state corresponding to the nucleophilic attack of the carbonyl on the silicon center. This attack then prompts the heterolytic cleavage of Si–H bond. The rate-determining energy of the S_N2-Si transition state is calculated to be 22.9 kcal/mol with benzaldehyde. In contrast, our calculations indicate that the initial silane addition to the nitrido ligand does not represent an intermediate of the catalytic process leading to the silyl ether products, since it involves high-energy transition states (29.2 and 37.8 kcal/mol) in the reduction of carbonyls. Moreover, the computational results show that the Ru^III–saldach species afforded by N–N coupling (with an activation barrier of 24.2 kcal/mol) of the nitridoruthenium­(VI) complex provides a competitive hydrosilylation reaction by favoring the ionic outer-sphere mechanistic pathway, associated with a significantly small activation barrier (3.7 kcal/mol). This study provides theoretical insight into the novel properties of the high-valent transition-metal Ru^VI–nitrido catalyst in catalytic reduction reactions

Theoretical Study of POCOP-Pincer Iridium(III)/Iron(II) Hydride Catalyzed Hydrosilylation of Carbonyl Compounds: Hydride Not Involved in the Iridium(III) System but Involved in the Iron(II) System

The catalytic hydrosilylation of carbonyl compounds by two POCOP-pincer transition-metal hydrides, (POCOP)­Ir­(H)­(acetone)⁺ (<b>1A-acetone</b>) and (POCOP)­Fe­(H)­(PMe₃)₂ (<b>1B</b>) (POCOP = 2,6-bis­(dibutyl-/diisopropylphosphinito)­phenyl), was theoretically investigated to determine the underlying reaction mechanism. Several plausible mechanisms were analyzed using density functional theory calculations. The <b>1A-acetone</b>-catalyzed hydrosilylation of carbonyl compounds proceeds via the ionic hydrosilylation pathway, which is initiated by the nucleophilic attack of the η¹-silane metal adduct by carbonyl substrate. This attack results in the heterolytic cleavage of the Si–H bond and the generation of a siloxy carbenium ion paired with a neutral iridium dihydride, [(POCOP)­Ir­(H)₂]­[R₃SiOCHR′]⁺, followed by transfer of hydride from the metal center to the siloxy carbenium ion to yield the silyl ether product. The activation energy of the turnover-limiting step was calculated as ∼15.2 kcal/mol. This value is energetically more favorable than those of other pathways by as much as 22.6 kcal/mol. The most energetically favorable process for the hydrosilylation of carbonyl compound catalyzed by POCOP-pincer iron hydride <b>1B</b> was determined as the carbonyl precoordination pathway, which involves the initial coordination of the carbonyl substrate to the metal center and subsequent migratory insertion into the M–H bond to give the alkoxide intermediate. This intermediate then undergoes M–O/Si–H σ-bond metathesis to yield the silyl ether product. The ionic hydrosilylation pathway requires an activation energy that is ∼30.0 kcal/mol higher than that of the carbonyl precoordination pathway. Our calculation results indicate that the hydride moiety is not involved in the POCOP-pincer iridium­(III) hydride <b>1A-acetone</b>-catalyzed hydrosilylation of carbonyl compounds but is involved in the POCOP-pincer iron­(II) hydride <b>1B-</b>catalyzed process

Hydrosilylation of Carbonyls Catalyzed by the Rhenium(V) Oxo Complex [Re(O)(hoz)₂]⁺A Non-Hydride Pathway

Catalytic conversion of silane and carbonyls by the cationic rhenium oxo complex [Re­(O)­(hoz)₂]⁺ (<b>1</b>; hoz = 2-(2′-hydroxyphenyl)-2-oxazoline(1−)) was examined using density functional theory. It is shown that complex <b>1</b> catalyzed the carbonyl hydrosilylation via a non-hydride pathwaythe ionic hydrogenation mechanism. The complete catalytic cycle is proposed to involve three steps: the formation of <i>cis</i> η¹-silane Re­(V) adduct, the heterolytic cleavage of a Si–H bond through <i>anti</i> attack of carbonyls at the <i>cis</i> η¹-silane Re­(V) adduct, and transfers between the rhenium and activated silylcarbonium ion to produce the silyl ether product and regenerate catalyst <b>1.</b> The σ-bond metathesis like transition state suggested by Abu-Omar, although not located, can be inferred from the ionic hydrogenation transition states (<b>TS_3</b><i><b>syn</b></i> and <b>TS_5</b><i><b>syn</b></i>, in which the carbonyls <i>syn</i> attack the η¹-silane Re­(V) adduct) associated with the higher energy barrier

Hydrosilylation of Carbonyls Catalyzed by the Rhenium(V) Oxo Complex [Re(O)(hoz)₂]⁺A Non-Hydride Pathway

Catalytic conversion of silane and carbonyls by the cationic rhenium oxo complex [Re­(O)­(hoz)₂]⁺ (<b>1</b>; hoz = 2-(2′-hydroxyphenyl)-2-oxazoline(1−)) was examined using density functional theory. It is shown that complex <b>1</b> catalyzed the carbonyl hydrosilylation via a non-hydride pathwaythe ionic hydrogenation mechanism. The complete catalytic cycle is proposed to involve three steps: the formation of <i>cis</i> η¹-silane Re­(V) adduct, the heterolytic cleavage of a Si–H bond through <i>anti</i> attack of carbonyls at the <i>cis</i> η¹-silane Re­(V) adduct, and transfers between the rhenium and activated silylcarbonium ion to produce the silyl ether product and regenerate catalyst <b>1.</b> The σ-bond metathesis like transition state suggested by Abu-Omar, although not located, can be inferred from the ionic hydrogenation transition states (<b>TS_3</b><i><b>syn</b></i> and <b>TS_5</b><i><b>syn</b></i>, in which the carbonyls <i>syn</i> attack the η¹-silane Re­(V) adduct) associated with the higher energy barrier

A novel state-of-charge estimation method of lithium-ion batteries combining the Grey model and Genetic Algorithms

In order to guarantee safe and reliable operation of battery in electric vehicles and utilizing capacity at the greatest extent, it is indispensable to estimate the state-of-charge (SoC) of battery. This study aimed to develop such a novel estimation approach based on the Grey model and Genetic Algorithms method without the need of a high computation cost and high-fidelity battery model. A SoC analytical model was established using the Grey System theory based on a limited amount of incomplete data compared to conventional methods. The model was further improved by applying the sliding window mechanism to adjust the model parameters according to the evolving operating status and conditions. In addition, the Genetic Algorithms were introduced to achieve an optimal adjustment coefficient, $\lambda$ , in the traditional Grey model (1, 1) model to further improve the source estimation accuracy. For experimental verification, two types of Lithium-ion batteries were used as the device-under-test, and the accuracy and repeatability of the proposed modeling method were verified under a range of battery discharging conditions. The results indicate that the proposed modeling approach features a higher accuracy for such systems compared to the benchmarking GM method that is illustrated using typical passenger car driving cycles

Point-of-Use SERS Approach for Efficient Determination and Removal of Phthalic Acid Esters Based on a Metal–Organic Framework-Coated Melamine Sponge

Phthalic acid esters (PAEs) are ubiquitous environmental contaminants, and their real-time monitoring and removal remain challenging. Herein, a point-of-use (POU) device integrating adsorption, surface-enhanced Raman spectroscopy (SERS), and removal strategy was developed and realized ultrafast on-site determination of PAEs and cleanup of them from water. A piece of flexible melamine sponge (MS) was coated with gold nanostars (AuNSs) and metal–organic frameworks (MOFs), thus obtaining SERS activity and adsorption capacity. Based on this multifunctional AuNSs@MOFs/MS composite, clear trends were observed between SERS signal intensity and concentration of di(2-ethylhexyl)phthalate (DEHP) and dibutyl phthalate (DBP). The method detection limits of DEHP and DBP were calculated to be 0.75 × 10–7 and 0.67 × 10–7 M in water, respectively, proving good sensitivity. Furthermore, this POU device exhibited satisfactory adsorption capacity (∼82.3 g/g for DBP and ∼90.0 g/g for DEHP), high adsorption efficiency (equilibrium in 100 s), and good regeneration capability (removal efficiency >70% after 5 cycles). The applicability of this device was verified by its good determination and removal performance in real environmental water matrices. The whole process could be completed within 5 min. This approach provides a new POU alternative for real-time monitoring and removal of PAEs in water

Data & Scripts for Chu et al. (2016) Nature Communications

This data file includes data and R scripts used to fit the vital rates models and to run simulations (IBM and IPM) for Chu et al. (2016) Nature Communications

Clinical Efficacy of Therapy with Recombinant Human Interferon α1b in Hand, Foot, and Mouth Disease with Enterovirus 71 Infection

<div><p>A rapid expansion of HFMD with enterovirus 71 infection outbreaks has occurred and caused deaths in recent years in China, but no vaccine or antiviral drug is currently available for EV71 infection. This study aims to provide treatment programs for HFMD patients. We conducted a randomized, double-blind, controlled trial and evaluated clinical efficacy of therapy with rHuIFN-α1b in HFMD patients with EV71 infection. There were statistical differences in outcomes including the fever clearance time, healing time of typical skin or oral mucosa lesions, and EV71 viral load of the HFMD patients among ultrasonic aerosol inhalation group, intramuscular injection group and control group. rHuIFN-α1b therapy reduced the fever clearance time, healing time of typical skin or oral mucosa lesions, and EV71 viral load in children with HFMD.</p><p><b><i>Trial Registration</i>:</b> Chinese Clinical Trial Registry <a href="http://www.chictr.org.cn/showprojen.aspx?proj=4422" target="_blank">ChiCTR-TRC-14005153</a></p></div