Borate Esters as Alternative Acid Promoters in the Palladium-Catalyzed Methoxycarbonylation of Ethylene

Ethylene Methoxycarbonylation over Heterogeneous Pt1/MoS2 Single-Atom Catalyst: Metal-Support Concerted Catalysis

Ethylene methoxycarbonylation (EMC) to methyl propanoate (MP) is an industrially important reaction and commercially uses a homogeneous Pd-phosphine organometallic complex as the catalyst and corrosive strong acid as the promoter. In this work, we develop a Pt1/MoS2 heterogeneous single-atom catalyst (SAC) which exhibits high activity, selectivity, and good recyclability for EMC reaction without need of any liquid acid. The production rate of MP achieves 0.35 gMP gcat-1 h-1 with MP selectivity of 91.1% at 1 MPa CO, 1 MPa C2H4, and 160 °C, which can be doubled at 2 MPa CO and corresponds to 320.1 molMP molPt-1 h-1, at least 1 order of magnitude higher than the earlier reported heterogeneous catalyst and even comparable to some of homogeneous catalyst. Advanced characterizations and DFT calculations reveal that all the Pt single atoms are located at the Mo vacancies along the Mo edge of the MoS2 nanosheets, forming pocket-like Mo-S-Pt1-S-Mo ensembles with uniform and well-defined structure. Methanol is first adsorbed and dissociated on Mo sites, and the produced H spillovers to the adjacent Pt site forming Pt-H species which then activate ethylene, forming Pt-ethyl species. Meanwhile, CO adsorbed on the other Mo site reacts with the Pt-ethyl species, yielding propionyl species, and this carbonylation is the rate-determining step. The final methoxylation step proceeds via the nucleophilic attack of propionyl species by -OCH3 affording the final product MP. Such a metal-support concerted catalysis enabled by the Mo-S-Pt1-S-Mo multisite ensemble opens a new avenue for SACs to promote the multimolecular reactions that prevail in homogeneous catalysis.

Ligand-Controlled Regiodivergent Thiocarbonylation of Alkynes toward Linear and Branched α,β-Unsaturated Thioesters

Thiocarbonylation of alkynes offers an ideal procedure for the synthesis of unsaturated thioesters. A robust ligand-controlled regioselective thiocarbonylation of alkynes is developed. Utilizing boronic acid and 5-chlorosalicylic acid as the acid additive to in situ form 5-chloroborosalicylic acid (5-Cl-BSA), and bis(2-diphenylphosphinophenyl)ether (DPEphos) as the ligand, linear α,β-unsaturated thioesters were produced in a straightforward manner. Switching the ligand to tri(2-furyl)phosphine can turn the reaction selectivity to give branched products. Remarkably, this approach also represents the first example on thiocarbonylation of internal alkynes.

Crystal structure of dichlorido(N-o-tolyl-1,1-di-p-tolylphosphanamine–κ1 P)-(methoxydi-p-tolylphosphane-κ1 P)palladium(II), C36H39Cl2NOP2Pd

C36H39Cl2NOP2Pd, orthorhombic, Pbca (no. 61), a = 19.209(13) Å, b = 15.144(11) Å, c = 24.011(19) Å, V = 6985(9) Å3, Z = 8, R gt(F) = 0.0292, wR ref(F 2) = 0.0867, T = 100 K.

Crystal structure of N,N-bis(diphenylphosphanyl)cyclohexylamine, C30H31NP2

C30H31NP2, monoclinic, P21/n, a = 15.8251(19) Å, b = 10.3667(12) Å, c = 15.900(2) Å, β = 107.225(3)°, V = 2491.5(5) Å3, Z = 4, R gt (F) = 0.0390, wR ref (F 2 ) = 0.0935, T = 163 K.

Ethylene tri- and tetramerization: a steric parameter selectivity switch from X-ray crystallography and computational analysis

A steric parameter (θN-sub) is introduced to describe the steric bulk at the nitrogen atom on a range of PNP ligands used in ethylene tri- and tetramerization. This parameter was calculated for the free ligands and different metal complexes thereof and compared to catalytic data. A specific tendency is observed for the value of θN-sub and 1-hexene selectivity, and a slight increase in 1-octene selectivity is found with increased bulkiness of the substituents on the nitrogen atom.

Tetra-kis(5,7-dimethyl-quinolin-8-olato-κ(2)N,O)zirconium(IV) dimethyl-form-amide disolvate

In the title compound, [Zr(C₁₁H₁₀NO)₄]·2C₃H₇NO, the Zr^IV ion is coordinated by four bidentate 5,7-dimethylquinolin-8-olate ligands in a slightly distorted square-anti­prismatic coordination environment. The asymmetric unit also contains two N,N′-dimethyl­formamide (DMF) solvent mol­ecules. In the crystal, a weak C—H⋯O hydrogen bond links the complex mol­ecule to a solvent mol­ecule and weak π–π stacking inter­actions [centroid–centroid distance = 3.671 (3) Å] also occur. One of the DMF solvent mol­ecules was refined as disordered over three sets of sites, with refined occupancies in the ratio of 0.391 (9):0.342 (10):0.267 (7).

Tricarbonylbis(triphenylphosphane-κP)iridium(I) hexafluoridophosphate methanol monosolvate

In the title compound, [Ir(C₁₈H₁₅P)₂(CO)₃]PF₆·CH₃OH, the Ir^I atom is coordinated by two triphenyl­phosphine ligands in axial sites and three carbonyl ligands in the equatorial plane of a fairly regular trigonal bipyramid: the equatorial C—Ir—C angles range from 115.45 (9) to 126.42 (10)°. The small deviations from the ideal tetra­hedral geometry around the P atoms are illustrated by C—P—C angles ranging from 104.08 (9) to 106.46 (9)°. In the crystal, the mol­ecules are linked by weak C—H⋯F, C—H⋯O and C—H⋯π inter­actions.