The 2V-P,N polymer supported palladium catalyst for methoxycarbonylation of acetylene

Co/SiO2 Catalyst for Methoxycarbonylation of Acetylene: On Catalytic Performance and Active Species

Reppe carbonylation of acetylene is an atom-economic and non-petroleum approach to synthesize acrylic acid and acrylate esters, which are key intermediates in the textile, leather finishing, and polymer industries. In the present work, a noble metal-free Co@SiO2 catalyst was prepared and evaluated in the methoxycarbonylation reaction of acetylene. It was discovered that pretreatment of the catalyst by different reductants (i.e., C2H2, CO, H2, and syngas) greatly improved the catalytic activity, of which Co/SiO2-H2 demonstrated the best performance under conditions of 160 °C, 0.05 MPa C2H2, 4 MPa CO, and 1 h, affording a production rate of 4.38 gMA+MP gcat-1 h-1 for methyl acrylate (MA) and methyl propionate (MP) and 0.91 gDMS gcat-1 h-1 for dimethyl succinate (DMS), respectively. Transmission electron microscopy (TEM), X-ray diffraction (XRD), and diffuse reflectance infrared Fourier transform spectra of CO adsorption (CO-DRIFTS) measurements revealed that an H2 reduction decreased the size of the Co nanoparticles and promoted the formation of hollow architectures, leading to an increase in the metal surface area and CO adsorption on the catalyst. The hot filtration experiment confirmed that Co2(CO)8 was generated in situ during the reaction or at the pre-activation stage, which served as the genuine active species. Our work provides a facile and convenient approach to the in situ synthetization of Co2(CO)8 for a Reppe carbonylation reaction.

The Formation of P-C Bonds Utilizing Organozinc Reagents for the Synthesis of Aryl- and Heteroaryl-Dichlorophosphines

Aryl- and heteroaryl-dichlorophosphines are mildly and selectively made in a one-pot synthesis in moderate to good yields starting from the respective aryl bromides or five-membered heterocycles, following lithiation with nBuLi, transmetalation with ZnCl₂, and subsequently the reaction with PCl₃. Selected aryl- and heteroaryl-dichlorophosphines were successfully synthesized using this reaction method and could easily be purified after isolation. The intermediate formation of the organozinc species is essential, as it prevents the formation of multiple substitution products. Important are also the reaction conditions: the usage of the proper solvent for the respective aromatic precursors and removal of the remaining salts by addition of a dioxane/pentane mixture. Depending on the solvent and steric demand of the substituent, mono- and bis-substitution products can be formed but formation also prevented. Hereby, different organozinc species might play an important role.

Synthesis of α,β-unsaturated carbonyl compounds by carbonylation reactions

Carbonylation reactions represent one of the most important tool box for the synthesis of α,β-unsaturated carbonyl compounds which are key building blocks in organic chemistry. This paper summarizes the most important advances in this field.

Controlled scrambling reactions to polyphosphanes via bond metathesis reactions

Triphosphanes R'₂PP(R)PR'₂ (9a,c: R = Py; 9b R = BTz), 1,3-diphenyl-2-pyridyl-triphospholane 9d and pentaphospholanes (RP)₅ (13: R = Py; 18: R = BTz) are obtained in high yield of up to 98% from the reaction of dipyrazolylphosphanes RPpyr₂ (5: R = Py; 6: R = BTz; pyr = 1,3-dimethylpyrazolyl) and the respective secondary phosphane (R'₂PH, R' = Cy (9a,b), ^t Bu (9c); PhPH(CH₂)₂PHPh (9d)). The formation of derivatives 9a-d proceeds via a condensation reaction while the formation of 13 and 18 can only be explained by a selective scrambling reaction. We realized that the reaction outcome is strongly solvent dependent as outlined by the controlled scrambling reaction pathway towards pentaphospholane 13. In our further investigations to apply these compounds as ligands we first confined ourselves to the coordination chemistry of triphosphane 9a with respect to coinage metal salts and discussed the observation of different syn- and anti-isomeric metal complexes based on NMR and X-ray analyses as well as quantum chemical calculations. Methylation reactions of 9a with MeOTf yield triphosphan-1-ium Cy₂MePP(Py)PCy₂ ⁺ (10 ⁺) and triphosphane-1,3-diium Cy₂MePP(Py)PMeCy₂ ²⁺ (11 ²⁺) cations as triflate salts. Salt 11[OTf]₂ reacts with pentaphospholane 13 in an unprecedented chain growth reaction to give the tetraphosphane-1,4-diium triflate salt Cy₂MePP(Py)P(Py)PMeCy₂ ²⁺ (19[OTf]₂) via a P-P/P-P bond metathesis reaction. The latter salt is unstable in solution and rearranges via a rare [1,2]-migration of the Cy₂MeP-group followed by the elimination of the triphosph-2-en-1-ium cation [Cy₂MePPPMeCy₂]⁺ (20 ⁺) to yield a novel 1,4,2-diazaphospholium salt (21[OTf]).

Dual-Ionically Bound Single-Site Rhodium on Porous Ionic Polymer Rivals Commercial Methanol Carbonylation Catalysts

Novel porous polymers can serve as self-supporting solid carriers and provide abundant coordination or charged sites for single-site metals, and thus are emerging as advanced functional materials in heterogeneous catalysis for various transformations traditionally catalyzed by homogeneous systems. A brief overview of the development of this heterogenization given, including the recent advances regarding electrovalent bonds by employing charged supports represented by porous ionic polymers (PIPs), which is exemplified herein with a novel single-site Rh₁ /PIP catalyst, featuring a new active site [Rh(CO)I₃ ]^2- dual-ionically bound onto a quaternary phosphonium cationic framework polymer, different from the single-ionically bound [Rh(CO)₂ I₂ ]^- in previous studies. Such a unique metal configuration of Rh₁ /PIP leads to excellent performance in vapor-phase methanol carbonylation, outperforming commercial homo- and heterogeneous catalysts.

Galvanic Replacement-Mediated Synthesis of Ni-Supported Pd Nanoparticles with Strong Metal-Support Interaction for Methanol Electro-oxidation

Herein, well-defined Pd nanoparticles (NPs) developed on Ni substrate (Pd NPs/Ni) are synthesized via a facile galvanic replacement reaction (GRR) route performed in ethaline-based deep eutectic solvent (DES). For comparison, a Pd NPs/Ni composite is also prepared by the GRR method conducted in an aqueous solution. The Pd NPs/Ni obtained from the ethaline-DES is catalytically more active and durable for the methanol electro-oxidation reaction (MOR) than those of the counterpart derived from conventional aqueous solution and commercial Pd/C under alkaline media. Detailed kinetic analysis indicates that the unique solvent environment offered by ethaline plays vital roles in adjusting the reactivity of the active species and their mass transport properties to control over the genesis of the Pd NPs/Ni nanocomposite. The resulting Pd NPs/Ni catalyst possesses a homogeneous dispersion of Pd NPs with a strong Pd (metal)-Ni (support) interaction. This structure enhances the charge transfer between the support and the active phases, and optimizes the adsorption energy of OH^- and CO on the surface, leading to superior electrocatalytic performance. This work provides a novel GRR strategy performed in ethaline-DES to the rational design and construction of advanced metal/support catalysts with strong interaction for improving the activity and durability for MOR.

Synthesis of MCM-41 Immobilized (Phenoxy)Imine Palladium(II) Complexes as Recyclable Catalysts in the Methoxycarbonylation of 1-Hexene

The immobilization of 2-phenyl-2-((3(tryethoxysicyl)propyl)imino)ethanol (HL1) and 4-methyl-2-(((3(triethoxysilyl)propyl)imino)methyl)phenol (HL2) on MCM-41 afforded the respective ligands HL1-MCM-41 (HL3) and HL2-MCM-41 (HL4). The treatment of complexes Pd(L1)2 and Pd(L2)2 with MCM-41 afforded the immobilized complexes (Pd(L1)2)-MCM-41 (1) and (Pd(L2)2)-MCM-41 (2) respectively. Separately, the reactions of HL3 and HL4 with Pd(NCMe)2Cl2 produced the immobilized complexes Pd(HL3)Cl2 (3) and Pd(HL4)Cl2 (4) respectively. The immobilized compounds were characterized by FT-IR, Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), energy-dispersive X-ray (EDX), Thermogravimetric Analysis (TGA) and X-ray Powder Diffraction (XRD). All the complexes (1–4) formed active catalysts in the methoxycarbonylation of 1-hexene to give linear and branched esters. The catalysts were recycled four times without the loss of catalytic activity. Hot filtration experiments established the absence of leaching, and the heterogeneous nature of the active species was derived from mercury drop experiments.

Acetylene in Organic Synthesis: Recent Progress and New Uses

Recent progress in the leading synthetic applications of acetylene is discussed from the prospect of rapid development and novel opportunities. A diversity of reactions involving the acetylene molecule to carry out vinylation processes, cross-coupling reactions, synthesis of substituted alkynes, preparation of heterocycles and the construction of a number of functionalized molecules with different levels of molecular complexity were recently studied. Of particular importance is the utilization of acetylene in the synthesis of pharmaceutical substances and drugs. The increasing interest in acetylene and its involvement in organic transformations highlights a fascinating renaissance of this simplest alkyne molecule.

Sequential Electrophilic Substitution Reactions of Tungsten-Coordinated Phosphenium Ions and Phosphine Triflates

ion of chloride from [W(CO)₅{PPhCl₂}] with AgOSO₂CF₃ leads to the phosphine triflate complex [W(CO)₅{PPhCl(OSO₂CF₃)}] which undergoes electrophilic substitution reactions with N,N-diethylaniline, anisole, N,N-dimethyl-p-toluidine, toluene, biphenyl, naphthalene, 2,7,9,9-tetramethyl xanthene, and allyltrimethylsilane to form the chlorophosphine complexes [W(CO)₅{PPhClR}], where R = p-diethylanilinyl, p-anisyl, 2-(N,N-dimethyl-4-methylphenyl), p-tolyl, p-phenylphenyl, 1-naphthyl, 4-(2,7,9,9-tetramethylxanthyl), and allyl. Abstraction of the second chloride with AgOSO₂CF₃ leads, in most cases, to the respective phosphine triflates [W(CO)₅{PPhR(OSO₂CF₃)}], which react with ferrocene to form the ferrocenyl phosphine complexes [W(CO)₅{PPhR(C₁₀H₉Fe)}]. The W(CO)₅ unit can be removed via photolysis in the presence of bis(diphenylphosphino)ethane to form metal-free phosphines.

Multidentate 2-pyridyl-phosphine ligands – towards ligand tuning and chirality

The incorporation of a variety of alcohols into (amino)pyridyl-phosphine frameworks provides access to a library of multidentate (alkoxy)pyridyl-phosphines. Their coordination chemistry with Cu^I is explored.

Multifunctional Single-Site Catalysts for Alkoxycarbonylation of Terminal Alkynes

A multifunctional copolymer (PyPPh2 -SO3 H@porous organic polymers, POPs) was prepared by combining acidic groups and heterogeneous P,N ligands through the copolymerization of vinyl-functionalized 2-pyridyldiphenylphosphine (2-PyPPh2 ) and p-styrene sulfonic acid under solvothermal conditions. The morphology and chemical structure of the copolymer were evaluated using a series of characterization techniques. Compared with traditional homogeneous Pd(OAc)2 /2-PyPPh2 / p-toluenesulfonic acid catalyst, the copolymer supported palladium catalyst (Pd-PyPPh2 -SO3 H@POPs) exhibited higher activity for alkoxycarbonylation of terminal alkynes under the same conditions. This phenomenon could be attributed to the synergistic effect between the single-site Pd centers, 2-PyPPh2 ligands, and SO3 H groups, the outstanding swelling properties as well as the high enrichment of the reactant concentration by the porous catalyst. In addition, the catalyst could be reused at least 4 times without any apparent loss of activity. The excellent catalytic reactivity and good recycling properties make it an attractive catalyst for industrial applications. This work paves the way for advanced multifunctional porous organic polymers as a new type of platform for heterogeneous catalysis in the future.

A triazine-phosphite polymeric ligand bearing cage-like P,N-ligation sites: an efficient ligand in the nickel-catalyzed amination of aryl chlorides and phenols

A reusable polymeric material containing P,N-ligation sites was prepared by a facile one-step route for application in transition-metal catalysis as a reusable P,N-ligand.