Activated platinum in gallium-based room-temperature liquid metals for enhanced reduction reactions

Room-temperature gallium-based liquid metals (LMs) have recently attracted significant attention worldwide for application in catalysis because of their unique combination of fluidic and catalytic properties. Platinum loading in LMs is expected to enhance the catalytic performance of various reaction systems. However, Pt-loaded methods for Ga-based LMs have not yet been sufficiently developed to improve the catalytic performance and Pt utilization efficiency. In this study, a novel method for the fabrication of Pt-incorporated LMs using Pt sputter deposition (Pt(dep)-LMs) was developed. The Pt(dep)-LMs contained well-dispersed Pt flakes with diameters of 0.89 ± 0.6 μm. The catalytic activity of the Pt(dep)-LM with a Pt loading of ∼0.7 wt% was investigated using model reactions such as methylene blue (MB) reduction and hydrogen production in an acidic aqueous solution. The Pt(dep)-LMs showed a higher MB reduction rate (three times) and hydrogen production (three times) than the LM loaded with conventional Pt black (∼0.7 wt%). In contrast to the Pt(dep)-LMs, solid-based Ga with a Pt loading of ∼0.7 wt% did not catalyze the reactions. These results demonstrate that Pt activation occurred in the Pt(dep)-LMs fabricated by Pt sputtering, and that the fluidic properties of the LMs enhanced the catalytic reduction reactions. Thus, these findings highlight the superior performance of the Pt deposition method and the advantages of using Pt-LM-based catalysts.

Highly efficient hydrogenation reduction of aromatic nitro compounds using MOF derivative Co–N/C catalyst

 A unique MOF derivative core–shell Co–N/C catalyst exhibits porous structure with high specific area, high cobalt content (23%) and high nitrogen content (3%), resulting in the excellent hydrogenation reduction of nitro compounds.

Water-soluble NHC-stabilized platinum nanoparticles as recoverable catalysts for hydrogenation in water

Aromatic compounds have been hydrogenated in water using recoverable catalysts based on water-soluble platinum nanoparticles capped with NHC ligands.

Enhanced Catalytic Performance for Hydrogenation of Substituted Nitroaromatics over Ir-Based Bimetallic Nanocatalysts

IrM (M = Fe, Co, and Ni) alloy nanoparticles (NPs) were synthesized in a solution by employing butyllithium as a reduction agent and oleylamine as a stabilizing agent, and the alumina-supported IrM bimetallic nanoparticles were tested for selective hydrogenation of various substituted nitroaromatics. The relevant characterizations including X-ray diffraction, X-ray photoelectron spectra, transmission electron microscopy, and diffuse reflectance fourier transform infrared with CO probes confirm that IrM NPs are uniform alloys. The obtained IrM/Al₂O₃ catalysts show significantly enhanced catalytic activity as well as selectivity relative to individual monometallic Ir catalysts, indicating a unique catalytic property of bimetallic alloy nanostructures. Among these bimetallic catalysts, IrNi/Al₂O₃ illustrate the highest activity and selectivity for hydrogenation of various substituted nitroaromatics. Calculations by density functional theory suggest that bimetallic structures of IrNi facilitate the reactant adsorption and product desorption, resulting in enhanced catalytic performance.

A carboxylic acid functionalized SBA-15 supported Pd nanocatalyst: an efficient catalyst for hydrogenation of nitrobenzene to aniline in water

The catalytic performance of a PdNPs/SBA-COOH has been investigated for the first time in the selective hydrogenation of nitrobenzene with hydrous hydrazine at RT in water medium.

Synthesis of [Pt12(CO)20(dppm)2]2- and [Pt18(CO)30(dppm)3]2- Heteroleptic Chini-type Platinum Clusters by the Oxidative Oligomerization of [Pt6(CO)12(dppm)]2

The reactions of [Pt₆(CO)₁₂]^2- with CH(PPh₂)₂ (dppm), CH₂═C(PPh₂)₂ (P^P), and Fe(C₅H₄PPh₂)₂ (dppf) proceed via nonredox substitution and result in the heteroleptic Chini-type clusters [Pt₆(CO)₁₀(dppm)]^2-, [Pt₆(CO)₁₀(P^P)]^2-, and [Pt₆(CO)₁₀(dppf)]^2-, respectively. Conversely, the reactions of [Pt₆(CO)₁₂]^2- with Ph₂P(CH₂)₄PPh₂ (dppb) and Ph₂PC≡CPPh₂ (dppa) can be described as redox fragmentation that afford the neutral complexes Pt(dppb)₂, Pt₂(CO)₂(dppa)₃, and Pt₈(CO)₆(PPh₂)₂(C≡CPPh₂)₂(dppa)₂. The oxidation of [Pt₆(CO)₁₀(dppm)]^2- results in its oligomerization to yield the larger heteroleptic Chini-type clusters [Pt₁₂(CO)₂₀(dppm)₂]^2-, [Pt₁₈(CO)₃₀(dppm)₃]^2-, and [Pt₂₄(CO)₄₀(dppm)₄]^2- (for the latter there is only IR spectroscopic evidence). All the clusters were characterized by means of IR and ³¹P NMR spectroscopies and electrospray ionization mass spectrometry. Moreover, the crystal structures of [NEt₄]₂[Pt₆(CO)₁₀(dppm)]·CH₃CN, [NEt₄]₂[Pt₁₂(CO)₂₀(dppm)₂]·2CH₃CN·2dmf, [NEt₄]₂[Pt₁₂(CO)₂₀(dppm)₂]·4dmf, [NEt₄]₂[Pt₆(CO)₁₀(dppf)]·2CH₃CN, Pt₂(CO)₂(dppa)₃·0.5CH₃CN, Pt₈(CO)₆(PPh₂)₂(C≡CPPh₂)₂(dppa)₂·2thf, and Pt(dppb)₂ were determined by single-crystal diffraction (dmf = dimethylformamide; thf = tetrahydrofuran).

Water soluble derivatives of platinum carbonyl Chini clusters: synthesis, molecular structures and cytotoxicity of [Pt12(CO)20(PTA)4]2- and [Pt15(CO)25(PTA)5]2-

The reactions of [Pt3n(CO)6n]2- (n = 2-5) homoleptic Chini-type clusters with increasing amounts of 1,3,5-triaza-7-phosphaadamantane (PTA) result in the stepwise substitution of one terminal CO ligand per Pt3 triangular unit up to the formation of [Pt3n(CO)5n(PTA)n]2- (n = 2-5). Competition between the nonredox substitution with retention of the nuclearity and the redox fragmentation to afford lower nuclearity heteroleptic Chini-type clusters is observed as a function of the amount of PTA and the nuclearity of the starting cluster. Because of this, [Pt12(CO)20(PTA)4]2- and [Pt15(CO)25(PTA)5]2- are more conveniently obtained via the oxidation of [Pt9(CO)15(PTA)3]2-. All the new species were spectroscopically characterized, and the structures of [Pt12(CO)20(PTA)4]2- and [Pt15(CO)25(PTA)5]2- were determined by single-crystal X-ray diffraction. These clusters may be viewed as heteroleptic Chini-type clusters composed of stacks of four and five Pt3(μ-CO)3(CO)2(PTA) units, respectively. The solubility in water of [Pt12(CO)20(PTA)4]2- and [Pt15(CO)25(PTA)5]2- has been determined and their cytotoxicity towards human ovarian (A2780) cancer cells and their cisplatin-resistant strain (A2780cisR) has been evaluated.

Monolayer Growth Front of Precious Metals through Insulating Mesoporous Membranes

Monolayers of precious metals are deposited within the pores of insulating mesoporous anodized aluminum oxide (AAO) membranes via a new electrochemical underpotential Cu deposition growth front mechanism, followed by spontaneous galvanic replacement of copper by platinum or iridium as demonstrated by XPS, ICP-OES, conductivity, and current analysis. Applications include fuel cells, hydrogen storage, flow batteries, and electrocatalytic conversions.

Microwave-activated Ni/carbon catalysts for highly selective hydrogenation of nitrobenzene to cyclohexylamine

Biocarbon supported Ni catalysts have been prepared by facile impregnation of Ni species by microwave-heating and used for selective hydrogenation of nitrobenzene to cyclohexylamine. These catalysts were characterized by X-ray diffraction, Raman spectra, N2 sorption measurement, X-ray photoelectron spectroscopy, temperature programmed reduction of H2 and H2 temperature-programmed desorption. The morphology and particle size of catalysts were imaged by scanning electron microscope and transmission electron microscope. For the hydrogenation of nitrobenzene to cyclohexylamine, 10%Ni/CSC-II(b) exhibits the best catalytic activity to achieve 100 mol% conversion of nitrobenzene and 96.7% selectivity of cyclohexylamine under reaction conditions of 2.0 MPa H2 and 200 °C, ascribed to high dispersion of Ni species and formation of nanosized Ni particles on the support aided by microwave-heating. Thus-prepared Ni/CSC catalyst is greatly activated, in which the addition of precious metal like Rh is totally avoided.

Reactions of Platinum Carbonyl Chini Clusters with Ag(NHC)Cl Complexes: Formation of Acid-Base Lewis Adducts and Heteroleptic Clusters

The reactions of anionic platinum carbonyl Chini clusters [Pt_3n(CO)_6n]^2- [n = 2 (1), 3 (2), 4 (3)] with Ag(IPr)Cl [IPr = C₃N₂H₂(C₆H₃ⁱPr₂)₂] afford the neutral acid-base Lewis adducts [Pt₉(CO)₁₈(AgIPr)₂] (4) and [Pt₆(CO)₁₂(AgIPr)₂] (5). These are thermally transformed into the homometallic heteroleptic neutral cluster [Pt₃(CO)₄(IPr)₂] (6). Alternatively, 6 can be obtained from the reactions of 1-3 with an excess of the free IPr carbene ligand. The formation of 6 is sometimes accompanied by trace amounts of [Pt₄(CO)₄(IPr)₃] (7). The reaction of 6 with free IPr affords the closely related [Pt₃(CO)₃(IPr)₃] (8) heteroleptic cluster by substitution of the unique terminal CO ligand with a third IPr ligand. The reactions of 1-3 with Ag(IMes)Cl [IMes = C₃N₂H₂(C₆H₂Me₃)₂] proceed differently from those involving Ag(IPr)Cl. Indeed, the only product isolated after workup is the bimetallic tetranuclear cluster [Pt₃(CO)₃(IMes)₃(AgCl)] (9). 9 slowly reacts under a CO atmosphere, resulting in the pentanuclear [Pt₅(CO)₇(IMes)₃] (10) complex. All of the new clusters 4-10 have been spectroscopically characterized and their molecular structures determined by X-ray crystallography. 4 and 5 retain the original trigonal-prismatic structures of the parent anionic Chini clusters, which are capped by two [Ag(IPr)]⁺ moieties. Conversely, 6-9 are based on a Pt₃ triangular core decorated by CO and N-heterocyclic carbene ligands as well as Pt(CO) (in the case of 7) and AgCl (9) moieties. 10 displays an edge-bridged tetrahedral geometry.

Heteroleptic Chini-Type Platinum Clusters: Synthesis and Characterization of Bis-Phospine Derivatives of [Pt3n(CO)6n]2- (n = 2-4)

The reactions of [Pt_3n(CO)_6n]^2- (n = 2-4) homoleptic Chini-type clusters with stoichiometric amounts of Ph₂PCH₂CH₂PPh₂ (dppe) result in the heteroleptic Chini-type clusters [Pt₆(CO)₁₀(dppe)]^2-, [Pt₉(CO)₁₆(dppe)]^2-, and [Pt₁₂(CO)₂₀(dppe)₂]^2-. Their formation is accompanied by slight amounts of neutral species such as Pt₄(CO)₄(dppe)₂, Pt₆(CO)₆(dppe)₃, and Pt(dppe)₂. A similar behavior was observed with the chiral ligand R-Ph₂PCH(Me)CH₂PPh₂ (R-dppp), and two isomers of [Pt₉(CO)₁₆(R-dppp)]^2- were identified. All the new species were spectroscopically characterized by means of IR and ³¹P NMR, and their structures were determined by single-crystal X-ray diffraction. The results obtained are compared to those previously reported for monodentate phosphines, that is, PPh₃, as well as more rigid bidentate ligands, that is, CH₂═C(PPh₂)₂ (P^P), CH₂(PPh₂)₂ (dppm), and o-C₆H₄(PPh₂)₂ (dppb). From a structural point of view, functionalization of anionic platinum Chini clusters preserves their triangular Pt₃ units, whereas the overall trigonal prismatic structures present in the homoleptic clusters are readily deformed and transformed upon functionalization. Such transformations may be just local deformations, as found in [Pt₉(CO)₁₆(dppe)]^2-, [Pt₉(CO)₁₆(R-dppp)]^2-, [Pt₁₂(CO)₂₂(PPh₃)₂]^2-, and [Pt₉(CO)₁₆(PPh₃)₂]^2-; an inversion of the cage from trigonal prismatic to octahedral, as observed in [Pt₆(CO)₁₀(dppe)]^2- and [Pt₆(CO)₁₀(PPh₃)₂]^2-; the reciprocal rotation of two trigonal prismatic units with the loss of a Pt-Pt contact as found in [Pt₁₂(CO)₂₀(dppe)₂]^2-.

Heterogenized Bimetallic Pd-Pt-Fe3O4 Nanoflakes as Extremely Robust, Magnetically Recyclable Catalysts for Chemoselective Nitroarene Reduction

A very simple synthesis of bimetallic Pd-Pt-Fe3O4 nanoflake-shaped alloy nanoparticles (NPs) for cascade catalytic reactions such as dehydrogenation of ammonia-borane (AB) followed by the reduction of nitro compounds (R-NO2) to anilines or alkylamines (R-NH2) in methanol at ambient temperature is described. The Pd-Pt-Fe3O4 NPs were easily prepared via a solution phase hydrothermal method involving the simple one-pot coreduction of potassium tetrachloroplatinate (II) and palladium chloride (II) in polyvinylpyrrolidone with subsequent deposition on commercially available Fe3O4 NPs. The bimetallic Pd-Pt alloy NPs decorated on Fe3O4 NPs provide a unique synergistic effect for the catalysis of cascade dehydrogenation/reduction. Various nitroarene derivatives were reduced to anilines with very specific chemoselectivity in the presence of other reducible functional groups. The bimetallic Pd-Pt-Fe3O4 NPs provide a unique synergistic effect for the catalysis of cascade dehydrogenation/reduction. The nitro reduction proceeded in 5 min with nearly quantitative conversions and yields. Furthermore, the magnetically recyclable nanocatalysts were readily separated using an external magnet and reused up to 250 times without any loss of catalytic activity. A larger scale (10 mmol) reaction was also successfully performed with >99% yield. This efficient, recyclable Pd-Pt-Fe3O4 NPs system can therefore be repetitively utilized for the reduction of various nitro-containing compounds.

Continuous-flow hydrogenation of olefins and nitrobenzenes catalyzed by platinum nanoparticles dispersed in an amphiphilic polymer

Continuous-flow hydrogenation of olefins and nitrobenzenes with ARP-Pt.

Insights into the hydrogenation mechanism of nitrobenzene to aniline on Pd3/Pt(111): a density functional theory study

The hydrogenation mechanism of nitrobenzene to aniline on Pd₃/Pt(111) surface preferentially follows the direct route and fits best the Jackson reaction mechanism (mechanism B).

Orchestrated photocatalytic hydrogen generation using surface-adsorbing iridium photosensitizers

Novel Ir-PSs with formyl bipyridyl ligands in different positions demonstrate hydrogen generation with much higher turnover numbers than the non-formyl bipyridyl Ir-PS.

RhNPs/SBA-NH2: a high-performance catalyst for aqueous phase reduction of nitroarenes to aminoarenes at room temperature

A RhNPs/SBA-NH₂ catalyst with <3 nm sized nanoparticles has been synthesized and used in the chemoselective hydrogenation of nitroarenes at room temperature in aqueous medium with N₂H₄·H₂O with high TOF.

Highly chemoselective reduction of aromatic nitro compounds by copper nanoparticles/ammonium formate

A highly chemoselective reduction of aromatic nitro compounds to the corresponding amino derivatives has been achieved by a combination of copper nanoparticles and ammonium formate in ethylene glycol at 120 degrees C. The reductions are successfully carried out in presence of a wide variety of other reducible functional groups in the molecule, such as Cl, I, OCH2Ph, NHCH2Ph, COR, COOR, CN, etc. The reactions are very clean and high yielding.