Selective hydrosilylation of styrene using an in situ formed platinum(1,3-dimesityl-dihydroimidazol-2-ylidene) catalyst

A highly active and selective in situ formed platinum(N-heterocyclic carbene) catalyst for the hydrosilylation of styrene with triethylsilane is described, which unlike all other known hydrosilylation catalysts, selectively yields hydrosilylation products, but (almost) no dehydrogenative silylation products.     

Hydroesterification of cyclohexene using the complex Pd(PPh3)2(TsO)2 as catalyst precursor: Effect of a hydrogen source (TsOH,H2O) on the TOF and a kinetic study (TsOH: p-toluenesulfonic acid)

The hydroesterification of cyclohexene is catalyzed by a preformed Pd(PPh₃)₂(TsO)₂ complex I in methanol as solvent. The effect of PPh₃, TsOH, and water on the TOF has been evaluated. The system I/PPh₃/TsOH=1/6/8, in the presence of 800 ppm of H₂O, at 373 K and under 2.0 MPa of CO leads to a TOF as high as 850 h⁻¹. The increase of TOF observed adding a hydride source such as TsOH and H₂O suggests that Pd-hydride species plays a key role in the first step of the catalytic cycle. The initial reaction rate increases linearly with the concentration of cyclohexene and of MeOH and passes through a maximum with increasing the pressure of CO. The rate equation r₀=k₁P_CO (1+k₂P_CO+k₃P_CO²)⁻¹ fits well the experimental data. The values of k₁, k₂, and k₃ have been evaluated at different temperatures. From the plot ln k versus 1/T, E₁=19.4 kcal/mol, E₂=20.6 kcal/mol and E₃=6.5 kcal/mol have been evaluated. On the basis of experimental evidences and of the kinetic study, a catalytic cycle mechanism has been proposed.     

Dimerization of 1,3-dienes in presence of Pd(diene)(PPh3)3 complex

Russian Chemical Bulletin -     

Crystal Structure of the Coordinatively Unsaturated 2-Pyridylphosphine Pd(0) Complex Pd(PPh2Py)3

The three-coordinate tris(2-pyridylphosphine)palladium(0) complex is the first example of a group 10 metal complex bearing pyridine substituted phosphine ligand, whose crystal structure is determined. Pd(PPh₂py)₃ crystallizes in the triclinic space group $ {\rm P}\bar 1 $, with a = 12.874(4) Å, b = 14.162(3) Å, c = 14.912(3) Å, α = 87.76(2)°, β = 66.50(2)°, γ = 63.17(2)°, Z = 2, and V = 2191(1) ų. Full-matrix least-squares refinement of 523 variables using 4911 data (F²_o > 3σF²_o) gave R = 0.033 and R_w = 0.033. The pyridine ring is disordered. Possible weak interactions among Ph rings or Py rings and Pd center are discussed. Close approach of the ortho hydrogen on phenyl rings to the Pd center may imply facile ortho metallation.     

Distinct reactivity of Pd(OTs)2: the intermolecular Pd(II)-catalyzed 1,2-carboamination of dienes

A Pd-catalyzed intermolecular 1,2-carboamination route to indolines from N-aryl ureas and 1,3-dienes that proceeds under mild conditions in relatively nonacidic media, is presented. The in situ generation, or preformation, of a palladium tosylate emerges as a key parameter in gaining the requisite reactivity for the C-H insertion/carbopalladation/nucleophilic displacement process.     

Pd(OAc)2/PPh3-Catalyzed Desulfonylative Homocoupling of Arylsulfonyl Chlorides

The Pd‐catalyzed homodimerization with respect to arylsulfonyl chlorides as an efficient method for the synthesis of biaryls has been developed. This desulfonylative reaction which was performed at reflux in 1,4‐dioxane for 4 h under air afforded the desired products in good to excellent yields.     

On the Synthesis and Characterization of Pd (CO) (PPh3)3

Pd (CO) (PPh₃)₃ could be isolated from the reaction mixture arising from cyclohexene hydrocarboxylation by PdCl₂ (PPh₃)₂ as the catalyst precursor; furthermore, it has also been prepared through direct reaction of Pd (PPh₃)₄ with CO in benzene. For this complex, ³¹P- and ¹³C-NMR. spectra suggest a rapid dissociation of PPh₃ at room temperature and a tetrahedral structure at – 70° in solution.     

Insertion of acetylenes in the PdPd bond of Pd2 (Ph2 PCH2 PPh2)2 Cl2

Dimethylacetylene dicarboxylate and hexafluoro-2-butyne add to Pd₂(dpm)₂Cl₂ (dpm = Ph₂PCH₂PPh₂) to give crystalline adducts Pd₂(dp)₂(μ-acetylene)Cl₂. An X-ray crystal structure of Pd₂(dpm)₂(μ-C₄F₆)Cl₂ reveals that the acetylene has inserted into the metalmetal bond and has been transformed into a cis-dimetallated olefin. The central CC bond length of the bridging olefin is 1.338(16) Å. The coordination about each of the two similar palladium ions is planar and involves two trans-phosphines (one from each of the bridging dpm ligands), a terminal chloride, and one carbon of the bridging olefin. Both Pd₂(dpm)₂Cl₂ and Pd₂(dpm)₂(μ-C₂{CO₂H₃}₂)Cl₂ catalyze the cyclotrimerization of dimethyl-acetylene dicarboxylate.     

Synthesen und Kristallstrukturen von [Pd9As8(PPh3)8] und [Pd9Sb6(PPh3)8]

Syntheses and Crystal Structures of [Pd₉As₈(PPh₂)₈] and [Pd₉Sb₆(PPh₃)₈] [PdCl₂(PPh₃)₂] reacts with As(SiMe₃)₃ to give the new cluster [Pd₉As₈(PPh₃)₈] ( 4 ). 4 has been characterized by X-ray crystal structure analysis. It is a molecule in which four [Pd₂(PPh₃)₂]-units are bridged by As₂-units. A further Pd atom is located in the centre of the cluster. 4 crystallizes in the space group C2/c with four formula units per unit cell. The lattice constants at 200 K are: a = 3 970.6(3), b = 1 648.90(16), c = 3 266.30(20) pm, β = 131,44(4)°. The reaction of [PdCl₂(PPh₃)₂] with Sb(SiMe₃)₃ yields [Pd₉Sb₆(PPh₃)₈] ( 5 ). 5 consists of a body centred cubic Pd₉-cluster. All of the cube faces are capped by μ₄-Sb-ligands. 5 crystallizes in the space group Pn3 with two formula units per unit cell. The lattice constants at 200 K are: a = b = c = 1 995.4(2) pm.     

Reduction of nitriles with 2-propanol in presence of RhCl(PPh3)3 and RuCl2(PPh3)3

Conclusions The complexes RhCl(PPh₃)₃ and RuCl₂(PPh₃)₃ catalyze hydrogen transfer from 2-propanol to the C N bond of benzonitrile and capronitrile. The reduction rate of the aromatic nitrile is higher than that of the aliphatic nitrile.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1894–1895, August, 1976.