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1.
Cationic Pd-complexes modified by dicyclohexyl{(R)-1-[(S)-2-(diphenylphosphino)ferrocenyl]ethyl}phosphine ( 1a ) give very active catalytic systems for the regioregular isotactic specific copolymerization of propene with CO. Other alk-1-enes also give stereoregular and regioregular copolymers, even if with lower productivity. The copolymers are isolated as poly(4-alkyl-tetrahydrofuran-2,2,5,5-tetrayl-2-oxy-2-methylenes) B in the solid state and give the isomeric poly(2-alkyl-1-oxopropane-1,3-diyls) A by dissolution in (CF3)2CHOH. Solid polymer A (R = Et) is formed back at least partially when the dissolved material is reprecipitated from MeOH. The use of the related (ferrocenyl)diphosphine ligands 1b ? e and 2 as the catalyst modifier shows that the presence of both elements of chirality and of large substituents on the P-atoms of the ligand is necessary to achieve good stereocontrol, and that the large difference in basicity between the two P-atoms is probably the reason for the good catalytic activity.  相似文献   

2.
Earlier studies on the [(1,2-bis(diphenylphosphino)ethane)rhodium]p+-catalyzed hydrogenation of 1-hexene and methyl-(Z)-α-acetamidocinnamate have been extended to catalysts containing larger chelating diphosphine ligands, i.e., Ph2P(CH2)nPPh2, where n = 3, 4 and 5. Comparisons include measurements of equilibrium constants for the binding of the olefinic substrates to the catalysts and of the catalytic hydrogenenation rates. Some related measurements also are reported for the corresponding catalyst systems containing the chiral ligand, 4R,5R-bis(diphenylphosphinomethyl)-2,2,-dimethyldioxalane (DIOP) and non-chelating PPh3 ligands.  相似文献   

3.
Copper diphosphine complexes have been found to be highly active and selective homogeneous catalysts for the hydrosilylation of CO2. The structure of the phosphine ligands strongly affects their catalytic activity. Turnover number (TON) reaches 70 000 after 24 hours with 1,2‐bis(diisopropylphosphino)benzene as a ligand under 1 atmosphere of CO2. 1H and 13C NMR spectra, carried out under the reaction conditions, showed the reaction mechanism through insertion of CO2 into Cu? H to afford Cu/formate species.  相似文献   

4.
The catalytic performances of Co‐Rh/Fe3O4 catalysts modified with phosphine ligands (PPh3) and its analogues on dicyclopentadiene hydroformylation were evaluated. Among these catalysts, Co‐Rh/Fe3O4 modified with tris(p‐trifluoromethylphenyl)phosphine was determined to be effective for monoformyltricyclodecanes production, whereas Co‐Rh/Fe3O4 modified with PPh3 or tri‐p‐tolylphosphine was effective for the diformyltricyclodecanes production. To investigate the ligand effects, the complex catalyst system (Co‐Rh/Fe3O4 and phosphine ligand) was subjected to pretreatment with syngas and then characterized by thermogravimetry and differential thermal analysis (TG‐DTA). It was determined that the threshold decomposition temperature reflected the corresponding Rh‐phosphine interaction strength, affecting the catalytic selectivity toward different products. A weak Rh‐phosphine interaction was desirable to produce monoformyltricyclodecanes with fast reaction kinetics, whereas a strong Rh‐phosphine complex was required for the synthesis of diformyltricyclodecanes. In addition to the selectivity rule shown in the PPh3 series, experiments with other ligands also demonstrated similar selectivity trends.  相似文献   

5.
The methylene spacers and an uncoordinated diphenylphosphine moiety in the scaffold of the CH3Si(CH2)n(PPh2)3 and Si(CH2PPh2)4-type silylated diphosphine Ni(II) complex systems have a marked impact on their catalytic performance in selective ethylene dimerization. Ni(II)-based precatalyst 1 , bearing two methylene spacers in its framework, exhibited the highest catalytic activity of 1.29 × 108 g (molNi)-1 h-1, while precatalyst 3 , with three methylene spacers, affords the highest product selectivity (88%) toward the C4 fraction. Crystallographic investigations revealed that the precatalyst 3 adopts the mononuclear bidentate binding mode and the steric constraints of its uncoordinated diphenylphosphine moiety may successfully tailor the catalytic environment of the catalyst. The precatalyst 4 may form a dinuclear complex and exhibits high catalytic activity by changing the ligand/Ni molar ratio. The high C4 selectivity of precatalyst 3 has been rationalized by density functional theory (DFT) calculations and found to be consistent with the experimental results. The study also revealed that designing new systems of Ni(II)-based complexes and their systematic modifications may further provide potential and industrially viable catalyst systems for selective ethylene oligomerization.  相似文献   

6.
Zinc complexes of chelating monoanionic N-donors and neutral diphosphine ligands were synthesized by reaction of diethylzinc with 1,3-diketimine, diazabutadiene, and diphosphine ligand precursors. These complexes were reacted with primary phosphines in an attempt to solicit phosphine dehydrocoupling reactivity. In most cases, insoluble zinc-containing precipitates were formed and ligands were liberated. For the most sterically encumbered complex, (DippL)ZnEt (3, DippL = [(2,6-iPrC6H3)NC(CH3)]2CH?), a product assigned as the zinc-phosphide (DippL)ZnPHPh (6) was observed but could not be isolated as a pure compound. A new, less bulky β-diketiminate complex (TolL)ZnEt (2, TolL = [(p-CH3C6H4)NC(CH3)]2CH?) was reacted with primary phosphines to give a precipitate and the bis(β-diketiminate)zinc complex (TolL)2Zn (5), an apparent product of comproportionation. (MesAI)ZnEt (1, MesAI = MesNC(Me)(Et)C(Me) = NMes) and 2 were structurally characterized.  相似文献   

7.
Novel phosphine oxides, (((3-methylpyridin-2-yl)amino)methyl)diphenylphosphine oxide (1) and diphenyl((pyrazin-2-ylamino)methyl)phosphine oxide (2), were synthesized and characterized. Phosphines ligands (3 and 4) were obtained by the reduction of 1 and 2 with AlH3, monitored by 31P NMR spectroscopy. Pd(II) complexes of 3 and 4 were synthesized and characterized (5 and 6). The catalytic activity of 5 and 6 was tested on the reaction of styrene with both activated and deactivated aryl bromides in air. The results of the catalytic experiments were discussed through DFT calculations.  相似文献   

8.
The new clusters [H4Ru4(CO)10(μ‐1,2‐P‐P)], [H4Ru4(CO)10(1,1‐P‐P)] and [H4Ru4(CO)11(P‐P)] (P‐P=chiral diphosphine of the ferrocene‐based Josiphos or Walphos ligand families) have been synthesised and characterised. The crystal and molecular structures of eleven clusters reveal that the coordination modes of the diphosphine in the [H4Ru4(CO)10(μ‐1,2‐P‐P)] clusters are different for the Josiphos and the Walphos ligands. The Josiphos ligands bridge a metal–metal bond of the ruthenium tetrahedron in the “conventional” manner, that is, with both phosphine moieties coordinated in equatorial positions relative to a triangular face of the tetrahedron, whereas the phosphine moieties of the Walphos ligands coordinate in one axial and one equatorial position. The differences in the ligand size and the coordination mode between the two types of ligands appear to be reflected in a relative propensity for isomerisation; in solution, the [H4Ru4(CO)10(1,1‐Walphos)] clusters isomerise to the corresponding [H4Ru4(CO)10(μ‐1,2‐Walphos)] clusters, whereas the Josiphos‐containing clusters show no tendency to isomerisation in solution. The clusters have been tested as catalysts for asymmetric hydrogenation of four prochiral α‐unsaturated carboxylic acids and the prochiral methyl ester (E)‐methyl 2‐methylbut‐2‐enoate. High conversion rates (>94 %) and selectivities of product formation were observed for almost all catalysts/catalyst precursors. The observed enantioselectivities were low or nonexistent for the Josiphos‐containing clusters and catalyst (cluster) recovery was low, suggesting that cluster fragmentation takes place. On the other hand, excellent conversion rates (99–100 %), product selectivities (99–100 % in most cases) and good enantioselectivities, reaching 90 % enantiomeric excess (ee) in certain cases, were observed for the Walphos‐containing clusters, and the clusters could be recovered in good yield after completed catalysis. Results from high‐pressure NMR and IR studies, catalyst poisoning tests and comparison of catalytic properties of two [H4Ru4(CO)10(μ‐1,2‐P‐P)] clusters (P‐P=Walphos ligands) with the analogous mononuclear catalysts [Ru(P‐P)(carboxylato)2] suggest that these clusters may be the active catalytic species, or direct precursors of an active catalytic cluster species.  相似文献   

9.
吴思忠  陆世维 《中国化学》2003,21(4):372-376
The catalytic performance of Ni(η^5-Ind)2 complex in the dimerization of propylene was studied in combimation with an organoaluminum co-catalyst,eventually in the presence of a phosphine ligand.The effects of the type of aluminum co-catalyst and its relative amount,the nature of phosphine ligand and P/Ni ratio as well as the reaction temperature were examined.The results indicated that the nickel precatalyst exhibited high productivity for the propylene dimerization together with organoaluminum.It was likely to strongly modify the reactivity in the catalytic sytem when using phosphine ligand as additives,especially at the reaction temperature below 0℃.The catalytic system based on Ni(η^5-Ind)2 complex displaed an extremely high productivity(TOF up to 16900h^-1)and a good regioselectivity to 2,3-dimethylbutenes (2,3-DMB) in dimers(66.4%)under proper reaction parameters.  相似文献   

10.
Me3NO activation of the methylidyne-bridged cluster HRu3(CO)10(μ-COMe) (1) in the presence of the unsaturated diphosphine ligand 2,3-bis(diphenylphosphino)maleic anhydride (bma) furnishes the bma-substituted cluster HRu3(CO)8(bma)(μ-COMe) (2) and the diphenylphosphine-substituted cluster HRu3(CO)8(Ph2PH)[μ-PPh2C=CC(O)OC(O)] (3) as the major and minor products, respectively. The 1H and 31P NMR data indicate that the bma ligand in cluster 2 is chelated to one of the ruthenium atoms that is bridged by the hydride and methylidyne ligands. Cluster 3 has been fully characterized in solution by IR and NMR spectroscopies, and the solid-state structure determined by X-ray crystallography. 3 crystallizes in the monoclinic space P21, a?=?12.1467(7)?Å, b?=?19.284(1)?Å, c?=?16.867(1)?Å, β?=?109.639(6)°, V?=?3721.0(4)?Å3, Z?=?4, and dcalcd?=?1.774?g?cm?3; R?=?0.0325, R w?=?0.0383 for 3518 reflections with I?>?3σ(I). The X-ray data confirm that one of the P–C(maleic anhydride) bonds of the bma ligand has been cleaved and that cluster 3 contains Ph2PH and μ-PPh2C=CC(O)OC(O) ligands, the latter which functions as a face-capping ligand to all three ruthenium atoms. Control experiments indicate that cluster 2 does not function as a precursor to cluster 3 under the employed reaction conditions.  相似文献   

11.
The catalytic system Pd/C—HCl is highly active in the reduction of mandelic acid derivatives to phenylacetic acid derivatives with carbon monoxide when the aromatic ring is para-substituted with a hydroxy group. Typical reaction conditions are: 70–110 °C, 20–100 atm of carbon monoxide, benzene—ethanol as reaction medium, substrate/Pd=102–104/1, HCl/substrate=0.3–0.8/1. [Pd] = 10−2 −10−4 M. When the catalytic system is used in combination with PPh3 a slightly higher activity is observed. Comparable results are observed when using a Pd(II) catalyst precursor such as PdX2, in combination with PPh3, or PdX2(PPh3)2 (XCl, AcO). When operating at 110 °C, decomposition to metallic palladium occurs. Pd(II) complexes with diphosphine ligands, such as diphenylphosphinemethane, -ethane, -propane or -butane, do not show any catalytic activity and are recovered unchanged. These observations suggest that Pd(0) complexes play a key role in the catalytic cycle. The proposed catalytic cycle proceeds as follows: the chloride ArCHClCOOR, formed in situ upon reaction of ArCHOHCOOR with hydrochloric acid, oxidatively adds to a Pd(0) species with formation of a catalytic intermediate having a Pd—[CH(Ar)COOR] moiety, which inserts a CO molecule, yielding an acyl intermediate of the type Pd—[COCH(Ar)COOR]. The nucleophilic attack of H2O on the carbon atom of the carbonyl ligand gives back the Pd(0) complex to the catalytic cycle and yields a phenylmalonic acid derivative, which produces the final product, ArCH2COOR, upon CO2 evolution. Alternatively, protonolysis of the intermediate having a Pd—[CH(Ar)COOR] moiety yields directly the final product and a Pd(II) species, which is then reduced by CO to Pd(0). Moreover, no catalytic activity is observed when the Pd/C—HCl system is used in combination with any one of the above diphosphine ligands, probably because these ligands block the sites on the catalyst able to promote the catalytic cycle or because they prevent the reduction of Pd(II) to Pd(0). The influence of the following reaction parameters has been studied: concentration of HCl, PPh3, palladium and substrate, pressure of carbon monoxide, the temperature, reaction time and solvent. The results are compared with those obtained in the carbonylation of aromatic aldehydes to phenylacetic acid derivatives catalyzed by the same system, for which it has been proposed that the catalysis occurs via carbonylation of the aldehyde to a mandelic acid derivative as an intermediate, which is further reduced with CO to yield the final product.  相似文献   

12.
Palladium complexes bearing monodentate and bidentate phosphine ligands (1-7) were synthesised and used as catalyst precursors in the methoxycarbonylation of norbornene. The catalytic systems bearing ligands 1, 3 and 4 afforded excellent conversions (>99%) and selectivity of the ester (>99%). NMR investigations showed that using complex 1a as the precursor resulted in the protonated phosphine, 1-H(+), being formed under catalytic conditions and thus the addition of acid is not required for the activation of this system since the reaction involving the precursor with methanol under CO pressure produces 2 equivalents of HCl and leads to the formation of the active species. The protonation of ligand 4 under methoxycarbonylation conditions was also observed and the diprotonated diphosphine was isolated and characterised. This compound was tested as a ligand and acid source in a catalysis and provided excellent conversion and high selectivity to the ester.  相似文献   

13.
New aluminum alkyl complexes, supported by o‐phenylene‐derived phosphido diphosphine pro‐ligands [Ph‐PPP]‐H and [iPr‐PPP]‐H ([Ph‐PPP]‐H = bis(2‐diphenylphosphinophenyl)phosphine; [iPr‐PPP]‐H = bis(2‐diisopropylphosphinophenyl)phosphine) are reported. Compounds [Ph‐PPP]AlMe2 ( 1 ), [iPr‐PPP]AlMe2 ( 2 ), and [Ph‐PPP]AliBu2 ( 3 ) have been synthesized by reaction of the pro‐ligand with the appropriate trialkyl aluminum precursor and have been characterized by 1H, 13C and 31P NMR spectroscopy. The solution NMR data and theoretical calculations suggest for all complexes trigonal bipyramidal structures with C2v symmetry in which the phosphido diphosphine ligand acts as a κ3 coordinated ligand. All complexes promote the ring‐opening polymerization of ε‐caprolactone, L‐ and rac‐lactide. Polyesters with controlled molecular parameters (Mn, end groups) and low polydispersities are obtained. Upon addition of isopropanol, efficient binary catalytic systems for the immortal ring‐opening polymerization of the cyclic esters are produced. Preliminary investigations show the ability of these complexes to promote copolymerization of l ‐lactide and ?‐caprolactone to achieve copolymers whose microstructures are depending on the structure of the catalyst. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 49–60  相似文献   

14.
Three new propanedithiolate-type iron–sulfur complexes containing tris(aromatic)phosphine ligands, [{(μ-SCH2)2CH2}Fe2(CO)5L] (L?=?P(PhOMe-p)3, 1; P(PhMe-p)3, 2; P(PhF-p)3, 3), have been prepared through carbonyl substitution in the presence of Me3NO. The new complexes 1–3 were characterized by elemental analysis, IR, 1H, 13C{1H}, and 31P{H} NMR spectra. The molecular structures of 1–3 were unequivocally determined by single crystal X-ray diffraction, in which the tris(aromatic)phosphine coordinated to Fe resides in an apical position of the pseudo-square-pyramidal geometry. IR spectroscopy and X-ray crystallographic analysis for 1–3 have indicated that the highly electron rich tris(aromatic)phosphine ligands (where the corresponding electron-donating abilities display the following order of P(PhOMe-p)3?>?P(PhMe-p)3?>?P(PhF-p)3) result in a considerable red shift of the CO-stretching frequencies and a clear change of the Fe–Fe bond distances in 1–3.  相似文献   

15.
New cadmium(II) complexes with phosphine telluride ligands of the type CdX2(R3PTe)n [X?=?ClO4?, n?=?4: R?=?n-Bu (1), Me2?N (2), C5H10?N (3), C4H8?N (4) or OC4H8?N (5); X?=?Cl, n?=?2: R?=?n-Bu (6), Me2?N (7), C5H10?N (8), C4H8?N (9) or OC4H8?N (10)] have been synthesized and characterized by elemental analyses, IR and multinuclear (31P, 125Te, and 113Cd) NMR spectroscopy. In particular, the solution structures of these complexes were confirmed by 113Cd NMR at low temperature, which displays a quintuplet for each of the perchlorate complexes and a triplet for each of the chloride complexes due to coupling with four and two equivalent phosphorus atoms, respectively, indicating a four-coordinate tetrahedral geometry for the metal center. These multiplet features were further accompanied by one bond Te–Cd couplings, clearly showing that the ligand is coordinated to the metal through tellurium. The results are discussed and compared with those obtained for closely related phosphine chalcogenide analogs.  相似文献   

16.
考察了不同配体对原位合成的固载Ru基催化剂上CO2加氢合成HCOOH反应活性的影响, 对于以单齿三苯基类ZPh3分子为配体的催化剂, 活性大小顺序为: PPh3>AsPh3>NPh3. 以PPh3为配体时, 其相应的原位合成催化剂上HCOOH的TOF值为656 h-1. 其次, 双齿膦配体的使用能带来比单齿膦配体更高的活性. 以dppe [1,2-双(二苯基膦基)乙烷]为配体时, 其相应的原位合成催化剂上HCOOH的TOF值为1190 h-1. 量子化学的理论计算结果表明, 具有适中的σ给予性和π接受性, 较小的空间位阻, 较好的电子离域作用的PPh3配体性能优于其它单齿三苯基类配体. 而具有较好的电子离域作用, 并且有螯合作用的双齿膦配体性能优于单齿膦配体.  相似文献   

17.
New isocyanide ligands with meta‐terphenyl backbones were synthesized. 2,6‐Bis[3,5‐bis(trimethylsilyl)phenyl]‐4‐methylphenyl isocyanide exhibited the highest rate acceleration in rhodium‐catalyzed hydrosilylation among other isocyanide and phosphine ligands tested in this study. 1H NMR spectroscopic studies on the coordination behavior of the new ligands to [Rh(cod)2]BF4 indicated that 2,6‐bis[3,5‐bis(trimethylsilyl)phenyl]‐4‐methylphenyl isocyanide exclusively forms the biscoordinated rhodium–isocyanide complex, whereas less sterically demanding isocyanide ligands predominantly form tetracoordinated rhodium–isocyanide complexes. FTIR and 13C NMR spectroscopic studies on the hydrosilylation reaction mixture with the rhodium–isocyanide catalyst showed that the major catalytic species responsible for the hydrosilylation activity is the Rh complex coordinated with the isocyanide ligand. DFT calculations of model compounds revealed the higher affinity of isocyanides for rhodium relative to phosphines. The combined effect of high ligand affinity for the rhodium atom and the bulkiness of the ligand, which facilitates the formation of a catalytically active, monoisocyanide–rhodium species, is proposed to account for the catalytic efficiency of the rhodium–bulky isocyanide system in hydrosilylation.  相似文献   

18.
Irradiation of bis(phosphine) tetracarbonyl complexes L2M(CO)4 (M = Cr, Mo, W) in the presence of donor ligands (amine, nitrile, halide ion) leads, via loss of one phosphine ligand, to neutral (LL′M(CO)4) or ionic ([LM(CO)4X]?) metal carbonyl compounds. The use of this reaction as the first step in a general synthesis of unsymmetrically disubstituted derivatives of Group VIA hexacarbonyls is discussed.  相似文献   

19.
Geminally diaurated μ2‐aryl complexes have been prepared where gold(I) centers were bridged by the semirigid diphosphine ligands bis(2‐diphenylphosphinophenyl)ether (DPEphos) and 4,6‐bis(diphenylphosphanyl)dibenzo[b,d]furan (DBFphos). Diaurated complexes were synthesized in ligand redistribution reactions of the corresponding di‐gold dichlorides with di‐gold diaryls (six of them new) and silver(I) salts. Diaurated complexes were isolated as salts of the minimally coordinating anions SbF6? and ReO4?. Efforts to prepare salts of the tetraarylborate [B(3,5‐(CF3)2C6H3)4]? led to transmetalation from boron, with crystallization of the fluorinated aryl complex. The new complexes were characterized by multinuclear NMR, absorption and emission spectroscopies, 77 K emission lifetimes, and by combustion analysis; three are crystallographically characterized. Structures of geminally diaurated aryl ligands are compared to those of mono‐aurated analogues. Both crystal structures and density‐functional theory calculations indicate slight but observable disruptions of aryl ligand aromaticity by geminal di‐gold binding. An intermolecular aurophilic interaction in one structurally authenticated complex was examined computationally.  相似文献   

20.
Two Cd(II) coordination polymers constructed from tris(p-carboxylphenyl)phosphine oxide (H3TPO), [Cd(HTPO)(1,4-bix)·3H2O]n (1) and [Cd2(HTPO)(HBPO)(H2O)2]n (2) (1,4-bix = 1,4-bis(imidazol-1-ylmethyl)benzene, H3BPO = bis(4-carboxylphenyl)phosphinic acid), were synthesized and identified by IR, elemental analysis, and single-crystal X-ray diffraction analysis. The 1,4-bix ligand leads to 1 as a ladder-like 1D chain structure. In 2, adjacent Cd2 units are bridged by HBPO2– and HTPO2– ligands to form a 3D structure. The H3BPO ligand is formed from the in situ reaction of H3TPO. It is the first example from hydrated Cd(II) salt promoting partial hydrolysis of a phosphine oxide ligand. The thermal behavior and solid-state photoluminescence properties correlated with the corresponding structural features were investigated.  相似文献   

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