23523-33-3

The invention discloses a preparation method of bis(triphenyl phosphine)palladium bromide. The preparation method comprises following steps: 1, palladium bromide is dissolved with a hydrochloric acidsolution, and sodium bromide is added for stirring react

Noble metals are valued, critical elements whose chemical activation or recycling is challenging, and traditionally requires high temperatures, strong acids or bases, or aggressive complexation agents. By using elementary palladium and gold, demonstrated here is the use of mechanochemistry for noble-metal activation and recycling by mild, clean, solvent-free, and room-temperature chemistry. The process leads to direct, efficient, one-pot conversion of the metals, including spent catalysts, into either simple water-soluble salts or metal–organic catalysts.

Reported herein is a novel visible-light photoredox system with Pd(PPh3)4 as the sole catalyst for the realization of the first direct cross-coupling of C(sp3)?H bonds in N-aryl tetrahydroisoquinolines with unactivated alkyl bromides. Moreover, intra- and intermolecular alkylations of heteroarenes were also developed under mild reaction conditions. A variety of tertiary, secondary, and primary alkyl bromides undergo reaction to generate C(sp3)?C(sp3) and C(sp2)?C(sp3) bonds in moderate to excellent yields. These redox-neutral reactions feature broad substrate scope (>60 examples), good functional-group tolerance, and facile generation of quaternary centers. Mechanistic studies indicate that the simple palladium complex acts as the visible-light photocatalyst and radicals are involved in the process.

Experimental and computational efforts are reported which illuminate the mechanism of a novel boron version of the widespread Negishi coupling reaction that offers a new protocol for the formation of aryl/acyl C?B bonds using a bulky boryl fragment. The role of nucleophilic borylzinc reagents in the reduction of the PdII pre-catalysts to Pd0 active species has been demonstrated. The non-innocent behavior of the PPh3 ligands of the [Pd(PPh3)2Cl2] pre-catalyst under activation conditions has been probed both experimentally and computationally, revealing the formation of a trimetallic Pd species bearing bridging phosphide (PPh2?) ligands. Our studies also reveal the monoligated formulation of the Pd0 active species, which led us to synthesize related (η3-indenyl)Pd-monophosphine catalysts which show improved catalytic performances under mild conditions. A complete mechanistic proposal to aid future catalyst developments is provided.

The invention discloses an improved synthesis method of a palladium complex (X in a general formula is equal to Br or I) and belongs to the field of organic chemistry. The improved synthesis method is characterized by including: using PdCl2(PPh3)2 and sodium iodide or sodium bromide as raw materials, wherein a feeding molar ratio is 1:10; using dichloromethane and water as solvents according to a volume ratio of 1:1, reacting to obtain a product, and subjecting the product to extracting, washing and filtering to obtain high-quality PdX2(PPh3) palladium complex. The palladium complex is high in yield, the method is simpler, the raw materials are cheaper, and the method has good industrial application prospect.

The three-component reaction of a-halomethyl oxime ethers, boronic acids and carbon monoxide at atmospheric pressure catalyzed by tetrakis- (triphenylphosphine)palladium(0) gives efficiently unsymmetrical b-alkoxyimino carbonyl compounds with total control of the regioselectivity, in high yield and atomic economy. Simple commercially available starting materials are used in this synthetic procedure. The three components assembly takes place preferentially versus the competing direct coupling or other possible side reactions. The mechanism of the transformation was investigated by NMR and intermediate palladium(II) complexes were detected.

The catalytic system trans-[PdBr2(PPh3) 2]/NEt3/PPh3/LiBr is highly active and selective in the oxidative carbonylation of iPrOH to the corresponding oxalate using benzoquinone (BQ) as a stoichiometric oxidant. The oxalate is formed together with minor amounts of carbonate and acetone. The influence of each component in the catalytic system is discussed together with the influence of the concentration of BQ, reaction time, temperature and CO pressure. NEt3 neutralizes the acid released in the catalytic cycle, thus favouring the formation of a dicarboalkoxy intermediate. Added PPh 3 reacts with benzoquinone giving betaine, which is a base that contributes to a further enhancement of the catalytic activity. The Br - anion might coordinate the Pd(0) which is formed in the product forming step thus stabilizing it against decomposition and making its reoxidation easier and reentering into the catalytic cycle. The catalytic activity depends slightly only on the concentration of BQ, suggesting that either uncoordinated BQ is not involved in the slow step of the catalytic cycle or that BQ is strongly coordinated in these species. The catalytic activity toward oxalate increases upon increasing the concentrations of NEt3 and PPh3, whereas the selectivity toward carbonate and the formation of acetone remains practically constant. The increase of the pressure of CO has a similar effect, except that the formation of acetone is suppressed. It is suggested that at relatively high pressure of CO, a pentacoordinated species may be formed so that there is no place for any interaction between palladium and the C-H bond before the β-H elimination. Instead there is a nucleophilic intrasphere attack of the alkoxy ligand onto a CO ligand. After catalysis the precursor trans-[PdBr2(PPh3)2] has been detected, together with trans-[PdBr(COOiPr)(PPh3) 2] and [Pd(BQ)(PPh3)2]. PPh3 remains coordinated to the palladium centre during catalysis. A BQ- and halides-assisted catalytic cycle is proposed. In this cycle, the reoxidation occurs through the release of a proton from an ammonium salt or a phosphonium salt, which are formed during the catalysis, with reformation of the catalyst precursor.

The novel utility of the ligand exchange reaction between M-X and RC(O)X′ (X, X′ = halogen; R = aryl, alkyl) is described. The relative ΔGs (ΔΔGs) of the oxidative additions of acid halides RC(O)X to M(PPh3)2Ln (M = Pt, Pd) were determined using the halogen-exchange reactions between X of trans-M(X)[C(O)R](PPh3)2 and X′ of RC(O)X′. Experimental thermodynamics data are reasonably consistent with those obtained by density functional theory (DFT) calculations. Activation parameters obtained by experiments as well as a systematic DFT study supported the fact that reactions occurred through slightly distorted quadrangular pentacoordinated σ-bond metatheses, in which the Cl atom underwent a more indirect course than the Br atom. Moreover, exchange reactions were employed as the accessible prototype for the conversion of halogen ligands of nickel triad complexes into heavier halogen ligands.

New members of a novel class of metallasilatrane complexes [X-Si-(μ-mt)4-M-Y], with M=Ni, Pd, Pt, X=F, Cl, Y=Cl, Br, I, and mt=2-mercapto-1-methylimidazolide, have been synthesized and characterized structurally by X-ray diffraction and by 29Si solid-state NMR. Spin-orbit (SO) effects on the 29Si chemical shifts induced by the metal, by the sulfur atoms in the ligand, and by heavy halide ligands Y=Cl, Br, I were investigated with the help of relativistic density functional calculations. Operators used in the calculations were constructed such that SO coupling can selectively be switched off for certain atoms. The unexpectedly large SO effects on the 29Si shielding in the Ni complex with X=Y=Cl reported recently originate directly from the Ni atom, not from other moderately heavy atoms in the complex. With respect to Pd, SO effects are amplified for Ni owing to its smaller ligand-field splitting, despite the smaller nuclear charge. In the X=Cl, Y=Cl, Br, I series of complexes the Y ligand strongly modulates the 29Si shift by amplifying or suppressing the metal SO effects. The pronounced delocalization of the partially covalent M←Y bond plays an important role in modulating the 29Si shielding. We also demonstrate an influence from the X ligand on the 29Si SO shielding contributions originating at Y. The NMR spectra for [X-Si-(μ-mt) 4-M-Y] must be interpreted mainly based on electronic and relativistic effects, rather than structural differences between the complexes. The results highlight the sometimes unintuitive role of SO coupling in NMR spectra of complexes containing heavy atoms. All in a spin! The class of metallasilatrane complexes [X-Si-(μ-mt)4-M-Y] with M=Ni, Pd, and Pt, previously reported for X=Y=Cl (shown here), has been extended by new members with X=F and Y=Br and I. New synthetic routes, structural characterizations by X-ray diffraction, and 29Si solid-state NMR data are reported. Spin-orbit effects on the 29Si chemical shifts were investigated with the help of relativistic density functional calculations. Copyright

Homogeneous catalysis by palladium complexes with phosphorus(III) ligands of the carbonylation of o-xylylene dihalides in the presence of water to form 3-isochromanone has been studied. Triphenylphosphine was found to provide the most effective catalyst, and by-products and intermediates of systems containing this ligand have been investigated. 2-Indanone is one by-product but is unstable to decomposition under catalytic conditions. Excess PPh3 is necessary to prolong activity of the catalyst but is also transformed to bis-phosphonium compound [o-C6H4(CH2PPh3)2]X2 (X = Cl or Br); this quaternization has been investigated and the structure of the bromide salt determined by X-ray diffraction. An unstable oxidative addition product of Pd(PPh3)4 was detected as a probable intermediate and related to the previously reported but catalytically-inactive complex trans-Pd(o-CH2C6H4CH2Cl)Cl(PMe3)2, which has been structurally characterized by X-ray diffraction in this work.

Halide ions react with PdX2(PPh3)2 (X = Cl, Br, I) complexes in an equilibrated reaction in which the phosphane ligand is substituted by the halide X- to form anionic complexes PdX3(PPh3)s

A new synthetic method, i.e. the palladium-catalyzed diastereoselective alkynylation reaction of (E)/(Z)-1,2-dibromoethylene, 9, has been developed to conveniently prepare (E)-1-bromo-1-alken-3-ynes (12) and 1,6-di(hetero)aryl- or 1,6-dialkyl-substituted (E)-3-en-1,5-diynes (13) with very high stereoisomeric purity.Compounds 12 and 13 can be obtained selectively according to the molar ratio between the reagents.Evidence has been obtained that the diastereoselectivity of these alkynylation reactions can be attributed to a diastereoselective oxidative addition of (E)/(Z)-9 to the palladium(0) complex used as catalyst in these reactions.It has also been shown for the first time that the complexes which derive from the oxidative addition of (E)-9 or (E)-1,2-dibromo-1,2-diphenylethylene, 14, to Pd(PPh3)4 easily undergo decomposition affording both PdBr2(PPh3)2 and acetylene or diphenylacetylene, 19, respectively.Finally, it has been shown that the reaction of 14 with organozinc derivatives, in the presence of catalytic amounts of 11, affords diphenylacetylene, 19, selectively, instead of cross-coupling products.

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Crown-functionalized triarylphosphines and their palladium complexes were synthesized and characterized.The palladium complexes were found to fulfil the concerted function of the transition metal catalyst and the phase transfer catalyst in the two-phase reduction of 1-chloromethylnaphthalene with formate salts.