Hydrogenation Of Acetophenone Research Articles

Application of phthalocyanine complexes of Cu(II), Co(II), Ni(II), and Zn(II) as catalysts in the transfer hydrogenation of acetophenone and its derivatives

In this study, tetra substituted metallophthalocyanines (M: Ni, Zn, Co, and Cu) containing imine and azo groups were synthesized using microwave irradiation. The structures of all complexes have been totally characterized via 1HNMR , 13CNMR , TGA/DTA, LC-MS/MS, elemental analysis, UV–Vis, FT-IR spectroscopy. The comparison of the catalytic features of phthalocyanine based on metals is also discussed briefly. These phthalocyanine-complexes were also used in the transfer hydrogenation (TH) of acetophenone derivatives in the existence of KOH, utilizing isoPrOH as a hydrogen source. Acetophenone compounds determined a TH of up to 99 % conversion. Copper phthalocyanines were first used as catalysts in transfer hydrogenation reactions. The Cu(II) complexes showed higher catalytic activity, converting up to 97 % at 1.0 mol% catalyst loading. Furthermore, we have discovered that the catalytic characteristics of this class of molecules are significantly influenced by both steric and electronic variables.

Cyclometalated and NNN Terpyridine Ruthenium Photocatalysts and Their Cytotoxic Activity.

The cyclometalated terpyridine complexes [Ru(η2-OAc)(NC-tpy)(PP)] (PP = dppb 1, (R,R)-Skewphos 4, (S,S)-Skewphos 5) are easily obtained from the acetate derivatives [Ru(η2-OAc)2(PP)] (PP = dppb, (R,R)-Skewphos 2, (S,S)-Skewphos 3) and tpy in methanol by elimination of AcOH. The precursors 2, 3 are prepared from [Ru(η2-OAc)2(PPh3)2] and Skewphos in cyclohexane. Conversely, the NNN complexes [Ru(η1-OAc)(NNN-tpy)(PP)]OAc (PP = (R,R)-Skewphos 6, (S,S)-Skewphos 7) are synthesized in a one pot reaction from [Ru(η2-OAc)2(PPh3)2], PP and tpy in methanol. The neutral NC-tpy 1, 4, 5 and cationic NNN-tpy 6, 7 complexes catalyze the transfer hydrogenation of acetophenone (S/C = 1000) in 2-propanol with NaOiPr under light irradiation at 30 °C. Formation of (S)-1-phenylethanol has been observed with 4, 6 in a MeOH/iPrOH mixture, whereas the R-enantiomer is obtained with 5, 7 (50-52% ee). The tpy complexes show cytotoxic activity against the anaplastic thyroid cancer 8505C and SW1736 cell lines (ED50 = 0.31-8.53 µM), with the cationic 7 displaying an ED50 of 0.31 µM, four times lower compared to the enantiomer 6.

Mechanistic Insights of the Ir‐bipyridonate Catalyzed Aqueous Methanol Dehydrogenation and Transfer Dehydrogenation to Acetophenone: Experimental and DFT Study

AbstractThe mechanisms of the Cp*IrIII(bpyOO)‐catalyzed (bpyOO=bidentate (NN) doubly deprotonated 2,2′‐bipyridine‐6,6′‐diol) acceptorless methanol dehydrogenation and acetophenone transfer hydrogenation by methanol under basic conditions have been explored by the combination of 1H NMR, kinetics, and DFT computational studies. During dehydrogenation of methanol and of its dehydrogenated derivatives, the presence of two iridium hydride species (anionic [Cp*Ir(bpyOO)H]−, C* and neutral [Cp*Ir(bpyOOH)H], D*), which interconvert depending on pH, was detected. The DFT studies on a Cp model system highlighted three interrelated catalytic cycles of methanol, formaldehyde and formic acid dehydrogenation, all leading to the same hydride intermediates C and D. The dehydrogenation of methanol prefers a direct β‐hydride transfer pathway from the methoxide ion to Ir, rather than the classical β‐hydride elimination pathway from a coordinated methoxide ligand, but an alternative bifunctional H+/H− transfer with involvement of a ligand O atom may become competitive at lower pH. The transfer hydrogenation of acetophenone using methanol as hydrogen source features species C* as resting state, with the acetophenone reduction being rate‐determining and following the reverse pathway of methanol oxidation, with a first‐order acetophenone decay and a kinetic isotope effect of 2.36±0.09.

Promoting Catalytic Performance Involving Hydrogen Spillover by Ion Exchange of Pt@A Catalysts to Regulate Reactant Adsorption.

Zeolite-encapsulated metal nanoparticle systems have exhibited interesting catalytic performances via the hydrogen spillover process, yet how to further utilize the function of zeolite supports to promote catalytic properties in such a process is still challenging and has rarely been investigated. Herein, to address this issue, the strategy to strengthen the adsorption energy of reactant onto the zeolite surface via a simple ion exchange method has been implemented. Ion-exchanged linde type A (LTA) zeolite-encapsulated platinum nanoclusters (Pt@NaA, Pt@HA, Pt@KA, and Pt@CaA) were prepared to study the influence of ion exchange on the catalytic performance in the model reaction of hydrogenation of acetophenone to 1-phenylethanol. The reaction results showed that the Pt@CaA catalyst exhibited the best catalytic activity in the series of encapsulated catalysts, and the selectivity of 1-phenylethanol approached 100%. As revealed by density functional theory (DFT) calculations and acetophenone temperature-programmed desorption (acetophenone-TPD) experiments, in comparison with introduced cations of Na+, H+, and K+, ion-exchanged Ca2+ on the zeolite maximumly enhanced the adsorption of carbonyl groups in acetophenone, playing a critical role in achieving the highest activity and excellent catalytic selectivity among the Pt@A catalysts.

Influence of Charge Delocalization on Manganese Catalyzed Transfer Hydrogenation

AbstractHydrogen transfer reactions promoted by Mn(I)‐based catalysts are a recently emerged field of research. Herein, we demonstrate the crucial effect of charge delocalization on the catalytic activity in transfer hydrogenation. Therefore, we synthesized pyridyl‐pyrazole ligands and a pyridyl‐pyridazinone ligand which exhibit resonance structures upon deprotonation with varying capability to transfer charge to the manganese center. The corresponding Mn(I) complexes were characterized and their activity as catalyst in transfer hydrogenation of acetophenone was determined using in‐situ IR techniques. Kinetic data and DFT calculations reveal that the ligands are deprotonated throughout the catalytic cycle and that the catalysts in which resonance structures point towards more negative charge at the metal center are also the more active ones. Thus, we deliver ample evidence that for effective hydrogen transfer the manganese catalyst requires a ligand with a deprotonable moiety allowing efficient delocalization to the metal while geometrical access of the acidic proton to the substrate is not essential. Our findings highlight the importance of an anionic hydrido intermediate, where mesomerism allows an effective charge transfer to the metal. This may support the ongoing development of new manganese‐based catalysts.

Biological assays, electrochemical behavior, and theoretical DFT calculations of Ru(II) complexes of chiral phosphinite based based on β-amino alcohols: Transfer hyrogenation of ketones using a HCOOH/Et3N mixture

Synthesis of two phosphinite ligands based on β-amino alcohols, in high yields has been demonstrated. When we treated [Ru(arene)(μ-Cl)Cl]2 {arene:p-cymene,benzene} with chelating phosphinite ligands, we obtained neutral Ru(II)-complexes possessing the general formula [Ru(arene)phosphiniteCl2]. The structure of the ligands and complexes was confirmed using analytical and spectroscopic techniques. The quantum chemical calculations were carried out for the ruthenium complexes at the DFT/CAM-B3LYP level of theory in gas phase. The phosphinite complexes were subjected to cyclic voltammetry studies in order to determine the energies of HOMO and LUMO levels and to estimate their electrochemical and some electronic properties. Organic complex-based memory substrates were immobilized using TiO2-modified ITO electrodes, and the memory functions of phosphinite-based organic complexes were verified by chronoamperometry (CA) and open-circuit potential amperometry (OCPA). In the present study, the antioxidant potentials of ruthenium-based p-cymene and benzene complexes through DPPH radical scavenging, metal chelating, and reducing power activities were also determined. In addition, DNA binding abilities and antimicrobial activities of these complexes against pathogenic bacteria were studied. Finally, the ruthenium complex, (2S)-1-{[(2S)-2-[(diphenylphosphanyl)oxy]propyl][(1R)-1-phenylethyl]amino}propan-2-yldiphenyl phosphinitobis[dichloro(η6-benzene)ruthenium(II)] also catalyzed asymmetric transfer hydrogenation of acetophenone with high conversion (up to 99%) and good enantioselectivity (ee up to 89 %), in the existence of formic acid and triethylamine in dichloromethane medium under air atmosphere.

Photocatalytic hydrogenation of acetophenone over Pd–TiO2 using saccharides as hydrogen sources

Acetophenone was converted to 1-phenylethanol over a Pd–TiO2 photocatalyst using various saccharides without the use of hydrogen gas, indicating that various saccharides can be used instead of hydrogen gas in this photocatalytic hydrogenation system.

A study of ruthenium-based catalysts used in homogeneous transfer hydrogenation of acetophenone

A study of ruthenium-based catalysts used in homogeneous transfer hydrogenation of acetophenone

Facet-dependent catalytic activity of shape-controllable palladium nanocrystals with clean surface in acetophenone selective hydrogenation

Shape-controlled metal nanocrystals have wide applications in catalysis. However, the capping agents playing significant roles in the shape-controlled synthesis often remain on the nanocrystal surfaces and are difficult to be removed completely, which not only causes the decrease in activity but also hinders the establishement of the correlation between various facets and intrinsic activity. In our present work, surface-clean Pd nanocrystals enclosed by different facets without capping agents were successfully synthesized by simply tuning the reduction kinetics in ascorbic acid mediated reduction of H2PdCl4 in water system. It was found that the turnover frequency (TOF) in acetophenone selective hydrogenation decreased with the decrease of the percentage of Pd{100} facet exposed in the Pd nanocrystals. The TOF value on Pd{100} facet was found 10 times higher than that on Pd{111} facet, while Pd{110} facet was found not favorable for acetophenone hydrogenation. Density functional theory (DFT) calculations reveal the more negative adsorption energy of acetophenone, the relatively shorter OPd distance between carbonyl group and the Pd surface, along with the much lower energy barrier in the acetophenone hydrogenation reaction, which leads to the Pd{100} surface exhibiting much higher TOF value than the other two surfaces. As for the Pd{110} surface, the long OPd distance, together with the large energy barrier makes it not favorable for the acetophenone hydrogenation.

Catalytic Transfer Hydrogenation Performance of Magnesium-Doped ZrO2 Solid Solutions

This is the first study to investigate the activity of a solid solution containing magnesium ions in a zirconia matrix in the catalytic transfer hydrogenation (CTH) of acetophenone with 2-pentanol. The results have shown that magnesium oxide is very highly active in CTH when physically mixed with zirconia. However, the same concentration of Mg2+ ions (Mg:Zr = 3:97) inserted into a zirconia lattice did not yield high activity in CTH. A higher concentration of Mg2+ ions (5%) was also tested in the two types of systems, i.e., a physical mixture of oxides and a solid solution. The increase in the concentration of Mg2+ ions in the physical mixture led to a pronounced increase in the activity of the system, whereas in the case of the solid solution it led to a slight decrease in activity. The impact of the zirconyl salt used in the synthesis was also examined, but showed little effect on the properties and activity of the systems. The study has also shown that the increase of the concentration of magnesium ions caused a decrease in the m-ZrO2 to t-ZrO2 ratio. Nevertheless, the rate of heating had an even bigger effect on this ratio.

Synthesis of half-sandwich ruthenium(II) and iridium(III) complexes containing imidazole-based phosphinite ligands and their use in catalytic transfer hydrogenation of acetophenone with isopropanol

Two ionic liquids (3-(3‑chloro-2-hydroxypropyl)-1-vinyl-1H-imidazol-3-ium chloride and 3-(3‑chloro-2-hydroxypropyl)-1‑butyl‑1H-imidazol-3-ium chloride) were prepared from commercially available, inexpensive 1-vinyl imidazole or 1‑butyl imidazole, respectively, in ethanol at room temperature. Then, these ionic liquids were treated with PPh2Cl to obtain ionic liquid-based phosphinite ligands and the reaction of these phosphinites with [Ru(η6-benzene)(μ-Cl)Cl]2, [Ru(η6−p-cymene)(μ-Cl)Cl]2, or [Ir(η5-C5Me5)(μ-Cl)Cl]2 gave the corresponding ruthenium and iridium complexes. Structures of the synthesized compounds were clarified by multinuclear NMR and IR spectroscopy as well as microanalysis. Furthermore, the complexes were applied as catalysts in the transfer hydrogenation of acetophenone derivatives to afford the corresponding alcohols with high conversions. Notably, [Ru(Ph2POC8H11N2Cl2)(η6-benzene)Cl2] acts as a good catalyst, giving the corresponding alcohols in 97–98% yields in 15 min at 82 °C (TOF ≤ 400 h−1) for the transfer hydrogenation reaction in comparison to analogous complexes. The catalysts are also useful for a variety of related ketone substrates with various electronic and steric regulating groups.

Synthesis, spectroscopic characterization, crystal structure, DFT and Hirschfeld surface analysis of a manganese(I) complex ([Mn(P-NH-NH-P)(CO)2][BPh4

We report the synthesis of a new Mn—PNNP complex ([Mn(P-NH-NH-P)(CO)2][BPh4]) with an original approach for the synthesis of a previously reported PNNP ligand PPh2(o-C6H4)NHCH2CH2NH(o-C6H4)PPh2 using a new protocol in a less toxic solvent. The PNNP ligand forms a stable mononuclear Mn(I) complex in a low spin state with the additional coordination of two carbonyl groups. This new complex has been characterized by elemental analysis, 1H, 13C and 31P NMR spectroscopy, FTIR spectroscopy and HRMS studies. The molecular structure of the complex was determined by X—ray diffraction analysis, which confirmed its distorted octahedral geometry with the linear tetradentate ligand in a rare cis-α-configuration. Additionally, theoretical calculations were performed on the optimized structure of the complex using the functional-basis-set combination B3PW91/6―311++G (d, p)/SDD which showed good correlation with the experimental data. The frontier molecular orbital analysis revealed a large HOMO to LUMO gap (4.66 eV) as expected for a low spin, d6 octahedral metal complex with the HOMO concentrated on the Mn centre. The Hirschfeld surface analysis signalled the important intermolecular H…H and C…H interactions. A preliminary catalytic study of the complex on transfer hydrogenation of acetophenone was conducted.

Acetophenone hydrogenation and consecutive hydrogenolysis with Pd/CNT catalysts: Highlighting the synergy between single atoms and nanoparticles by kinetic modeling

Understanding the cooperative action of palladium nanoparticles (NPs) and palladium single atoms (SAs) supported on Nis essential for developing more efficient supported transition metal catalysts. In this work, the comparison of a series of Pd-catalysts on CNTs having the same palladium loading (∼1.4 wt%) but involving different and controlled SA/NP ratios (between 2 and 200) is described. The hydrogenation of acetophenone into 1-phenylethanol and its consecutive hydrogenolysis to ethylbenzene are the chosen test reactions. Appropriate kinetic modeling of these two consecutive reactions was performed and allowed a quantitative assessment of the activity differences between catalysts as well as the demonstration of a synergy between the two palladium species (SAs and NPs). The maximum activity was clearly dependent on the distribution of the surface palladium between SAs and NPs, and interestingly, different optima for the two reactions are evidenced. This work may offer a new perspective for the design and synthesis of supported transition metal catalysts with targeted catalytic performance.

Computational Study on a Transfer Hydrogenation Catalysed by a Ru(II) Bis‐Pyrazolyl Pyridine Complex

AbstractDensity functional calculations were performed to investigate the Ru‐catalysed transfer hydrogenation of acetophenone to 1‐phenylethanol using isopropanol as the reducing agent. The catalyst is [Ru(bpp)Cl2(PPh3)], where bpp is a tridentate bis‐pyrazolyl pyridine ligand. We studied an inner sphere monohydridic mechanism where the active Ru centre binds, in addition to bpp, one of the original ligands as a spectator, which can be either chloride or triphenylphosphine. In both cases, catalyst initiation appears to be feasible (with triphenylphosphine being the preferred spectator ligand) and the catalytic cycle is efficient with a small energetic span. For which one of the cases the calculated energetic span is smaller depends on the treatment of entropy in solution. Since pathways involving dissociation of charged ligands are not preferred, the product is formed by a fast proton transfer within the Ru coordination sphere, from a coordinated isopropanol to the product alcoholate. Subsequently, both product release and catalyst regeneration can be accomplished by the dissociation of the charge neutral product alcohol. The β‐hydride transfer from a coordinated isopropanolate anion to ruthenium is slightly different depending on whether there is a chloride or phosphine present trans to the alcoholate. In both cases, this step contains the transition state with the highest Gibbs energy.

Pt3Ti Intermetallic Alloy Formed by Strong Metal–Support Interaction over Pt/TiO2for the Selective Hydrogenation of Acetophenone

Pt₃Ti Intermetallic Alloy Formed by Strong Metal–Support Interaction over Pt/TiO₂for the Selective Hydrogenation of Acetophenone

Influence of Physicochemical Properties of Ni/Clinoptilolite Catalysts in the Hydrogenation of Acetophenone.

Heterogeneous catalytic hydrogenation is an interesting alternative to conventional methods that use inorganic hydrides. The hydrogenation of acetophenone under heterogeneous conditions with the supported catalysts based on Ni is the most useful due to its redox properties and lower cost. As is well-known, catalyst support can significantly affect catalyst performance. We have investigated the influence of various physical-chemical parameters on the selective reaction of the hydrogenation of acetophenone by using different nickel catalysts on clinoptilolite supports, in four different forms: natural, previously modified with NH3 (Ni/Z+NH4 +), with HNO3 (Ni/Z+H+), and thermally treated (Ni/Z 500 °C). In particular, our work focuses on determining the influence of the mentioned physical-chemical parameters on the percentages of conversion and the selectivity of the catalysis. This study aims to identify the combination of parameters that allows for obtaining the best catalytic results. The identification of the physical-chemical parameters that determine the percentages of conversion and selectivity allows us to design optimal catalysts.

Synthesis, structures, and properties of manganese(i) complexes featuring tridentate amidine-toting protic amine ligands

Cationic Mn(CO)3 complexes having a protic amine ligand with cyclic amidine side arms were prepared and their catalytic properties of transfer hydrogenation of acetophenone and electrochemical reduction of CO2 were compared.

SYNTHESIS OF NOVEL BIS(PHOSPHINO)AMINE-RUII(ACAC)2 COMPLEXES, AND INVESTIGATION OF CATALYTIC ACTIVITY IN TRANSFER HYDROGENATION

In this study, reactions of (PPh2)2NCH2CH2N(PPh2)2 (L1) and {(PPh2)2NCH2CH2}3N (L2) with [RuII(acac)2(CH3CN)2] led to the production of new dinuclear complex [Ru(acac)2]2(L1) (1) and trinuclear complex [Ru(acac)2]3(L2) (2). Complex 1 and 2 are excellent candidates for the role of catalyst precursors in the transfer hydrogenation (TH) of acetophenone and its derivatives. Compared to complex (1), the trinuclear complex (2) is an exceptional catalyst, producing the corresponding alcohols in 98–99% yields in 20 minutes at 80 oC (TOF≤300 h-1) for the TH process. A comparison of the catalytic properties of the complexes is also briefly discussed. Complex structures have also been characterized by combining nuclear magnetic resonance (NMR), Fourier transform infrared (FT-IR), and elemental analysis.

N,S-heterocyclic carbene containing benzothiazol-2-ylidene-Ru(II) and Pd(II) new complexes functionalized with butyl linked carbazole moiety: Synthesis, characterization and their catalytic efficiency and electropolymerizations

In contrast to the large number of polymeric N-heterocyclic carbenes (NHCs) there are relatively few examples of NHCs-containing conductive polymers. However, conducting polymers (CPs) could be excellent hosts for NHC compounds, as they can easily form polymer films electrochemically, and their optical & electrical properties can be easily tuned by electrochemically or changing bonding groups in their structure. In this work, the N,S-heterocyclic carbene (NHC) ligand precursor, N-(4-butylcarbazole)benzothiazolium bromide (1) was prepared by solvent-free alkylation of benzothiazole by 9-(4-bromobutyl)carbazole with high efficiency. The air- and moisture-stable new piano-stool Ru(II)-N,S-NHC (2) and PEPPSI type Pd(II)-N,S-NHC (3) complexes, were synthesized and characterized by 1H- and 13C NMR, FT-IR, UV–vis and ESI-MS spectroscopic methods and elemental analysis. Further confirmations of structural details for benzothiazolium salt (1) and its Ru(II)-N,S-NHC complex (2) were determined by X-ray single-crystal diffraction. The catalytic performance of the complexes (2 and 3) in transfer hydrogenation (TH) of acetophenone and Suzuki–Miyaura cross-coupling reactions of aryl bromides were also investigated, respectively. All compounds (1–3) were electrochemically polymerized and conducting polymer films with pendant carbene complex moieties were obtained. The electrical and optical properties of the resulting polymers were characterized via spectroelectrochemical studies.

Tuning the catalytic performance of Pt/SiO2 catalysts by CoOx modification for selective hydrogenations of unsaturated carbonyl compounds

Tailoring the interface between active metals and promoters to improve catalytic performance is a challenging issue for bicomponent catalysts. Herein, we developed a series of silica supported Pt-CoOx hybrid nanocatalysts though in situ oxidation of supported bimetallic PtCo nanoparticles (NPs) with different Pt/Co ratios. Focusing on the hydrogenation of acetophenone to 1-phenylethanol as the model reaction, the obtained Pt-CoOx/SiO2 catalysts showed superior activity and selectivity compared to Pt/SiO2, and the sample with a Co/Pt molar ratio of 1/3 performed the best. Our research showed that the CoOx on Pt not only changed its electronic and geometric properties, but also promoted the adsorption of reactants and the dissociation of H2. A further increase of the Co/Pt ratio to 1/1, however, reduced the activity due to blockage of the Pt surface.