- Combining organometallic and Werner-type coordination sites in highly preorganized heterobimetallic systems
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A first example of a novel class of preorganized bimetallic complexes is reported, in which both an organometallic CpMn(CO)2 fragment and a classical Werner-type coordination site are arranged in close proximity by means of a bridging pyrazolat
- R?der, Jens C,Meyer, Franc,Winter, Rainer F,Kaifer, Elisabeth
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- Novel heterobimetallic compounds with metal-metal bonds: The use of quinolyl-substituted metallocenes as tridentate ligands
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1,1′-Bis(quinolyl)ferrocene (1) and 1,1′-bis(quinolyl)ruthenocene (2) were prepared by palladium-catalyzed cross-coupling of zincated metallocenes ((C6H4ZnCl)2M; M = Fe, Ru) with 8-bromoquinoline. Both complexes can serve as tridentate ligands toward d10 metal ions. Their reactions with anhydrous zinc chloride or with tetrakis(acetonitrile)copper(I) tetrafluoroborate lead to the bimetallic complexes 3-6, in which the zinc or copper ion is coordinated in a tridentate manner by the metallocene derivative 1 or 2, respectively. Two different coordination modes of the ligands 1 and 2 were observed, both with a metal-metal bond as proved by X-ray analysis. The bond distances Fe - Zn in 3 and Ru - Zn in 4 are practically identical (2.56 A); the Ru - Cu bond in 6 is somewhat longer (2.63 ?). Whereas the zinc adducts 3 and 4 contain the metallocene ligand in a Cs-symmetric arrangement with a 4-fold-coordinated Zn atom, the Ru-Cu compound 6 has a C2 symmetry with a 3-fold-coordinated Cu atom. The heterobimetallic compounds 3 and 4 are the first structurally characterized ferrocene and ruthenocene derivatives containing a metal to zinc bond. The complexes 5 and 6 are, to the best of our knowledge, the first examples of adducts of ferrocene and ruthenocene derivatives with copper.
- Enders, Markus,Kohl, Gerald,Pritzkow, Hans
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- New donor-functionalized Cp ligands: Synthesis and complexation behaviour of quinoxalyl and benzothiadiazolyl systems
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Sodium cyclopentadienide reacts as nucleophile with 4,7-dibromo-2,1,3- benzothiadiazole (BTZ) and leads to the new donorfunctionalized ligand Cp BTZ. Related quinoxalyl Cp systems have been prepared using Pd-catalyzed coupling with zincated Cp-
- Schuhen, Katrin,Sieb, David,Wadepohl, Hubert,Enders, Markus
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- Synthesis and coordination behaviour of the new (8-quinolyl)cyclopentadienyl ligand
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8-Bromoquinoline reacts with zincated cyclopentadienyl derivatives of Fe, Mn, and Re in the presence of bis(triphenylphosphine)palladium(0) to yield the corresponding 8-quinolylcyclopentadienyl metal complexes. Tricarbonyl[η5-(8-quinolyl)cyclop
- Enders, Markus,Kohl, Gerald,Pritzkow, Hans
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- Diaryltriazenido Palladium(II) complexes derived from 1-(2-bromo-4-ethoxycarbonylphenyl)-3-phenyltriazenes
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1-(2-Bromo-4-ethoxycarbonylphenyl)-3-phenyltriazene (1) can easily be deprotonated yielding the corresponding triazenides of lithium, silver, or triethylammonium. The equimolar metathesis reaction of [(Ph3P)2PdCl2] with th
- Preusser, Silvio,Sch?nherr, Paul R.W.,G?rls, Helmar,Imhof, Wolfgang,Krieck, Sven,Westerhausen, Matthias
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- A Combined Experimental/Computational Study of the Mechanism of a Palladium-Catalyzed Bora-Negishi Reaction
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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.
- Campos, Jesús,Nova, Ainara,Kolychev, Eugene L.,Aldridge, Simon
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p. 12655 - 12667
(2017/09/18)
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- Pd(η3-1-PhC3H4)(η5- C5H5), an unusually effective catalyst precursor for heck-mizoroki and sonogashira cross-coupling reactions catalyzed by bis-phosphine palladium(0) compounds
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The compound Pd(η3-1-PhC3H4) (η5-C5H5) reacts essentially quantitatively with a variety of phosphines L to form cross-coupling catalysts of the type PdL2 and has recently been shown to be a much more effective catalyst precursor for Suzuki-Miyaura cross-coupling reactions in comparison to more commonly utilized precursors such as Pd(PPh3)4, Pd 2(dba)3, and Pd(OAc)2, which do not effectively generate two-coordinate species PdL2. This advantage is expected to apply also to e.g. Heck-Mizoroki and Sonogashira cross-coupling reactions, both of which are generally believed to be catalyzed by species of the type PdL 2. Therefore, comparisons of the efficacies of catalyst systems based on Pd(η3-1-PhC3H4)(η5- C5H5), Pd(PPh3)4, Pd 2(dba)3, and Pd(OAc)2 are made utilizing the conventional coupling reactions of aryl halides with methyl acrylate and styrene for Heck-Mizoroki coupling and with phenylacetylene for Sonogashira coupling. As anticipated, catalyst systems based on Pd(η3-1-PhC 3H4)(η5-C5H5) are found to be significantly more active.
- Fraser, Andrew W.,Jaksic, Bryan E.,Batcup, Rhys,Sarsons, Christopher D.,Woolman, Michael,Baird, Michael C.
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supporting information
p. 9 - 11
(2013/03/13)
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- Activation and transformation of white phosphorus by palladium(ii) complexes
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A reaction of bis(triphenylphosphine)palladium dibromide with white phosphorus in the presence of NaBPh4 selectively gives phosphorous acid H3PO3. The mechanism of the formation involves coordination of a white phosphorus molecule, ligand exchange, and hydrolysis of the coordinated P4 molecule in the coordination sphere of palladium.
- Kagirov,Voloshin,Rizvanov, I. Kh.,Sinyashin,Yakhvarov
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p. 1116 - 1118
(2011/02/16)
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- Reactivity of 2-Silyl- and 2-stannyl-substituted phosphirenes
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Two methodologies have been tested for the functionalization of phosphirenes. In the first one, the C-Si bond of a 2-silylphosphirene is activated by a substoichiometric quantity of fluoride ion (TBAF) in THF at -78 °C. Using this technique, it is possible to perform a protodesilylation or a functionalization by benzaldehyde. However, at room temperature with a stoichiometry of fluoride, a nucleophilic attack takes place at P, leading to a ring-opened fluorophosphine. Stille cross-coupling with a 2-stannylphosphirene in the presence of [PdL2] as a catalyst leads to an alkynylphosphine by [1,3] migration of tin from C to P.
- Panichakul, Duanghathai,Lim, Yi Wee,Mathey, Francois
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p. 1985 - 1987
(2010/06/18)
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- Influence of the dba substitution on the reactivity of palladium(0) complexes generated from Pd02(dba-n,n′ -Z) 3 or Pd0(dba-n,n′-Z)2 and PPha 3 in oxidative addition with iodobenzene
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The reactivity of Pd(0) complexes generated by addition of PPh3 (PPh3/Pd = 2, 4) to either Pd02(dban,n′- Z)3 (n,n′-Z = 4,4′-F, 4,4′-H, 4,4′-MeO, 3,3′,4,4′,5,5′-OMe) or Pd0(dba-n,n′-Z) 2 (n,n′-Z = 4,4′-Br, 4,4′-Cl, 4,4′-H, 4,4′-CH3, 3,3′,5,5′-OMe) in DMF is affected by the electron-donating or -accepting properties of the groups Z substituted on the aromatic rings of dba. Whatever the nature of Z, the unreactive major complexes Pd0(η2-dba-n,n′-Z)(PPh3)2 are formed, which are in equilibrium with the common reactive complex Pd 0(PPh3)2 and dba-n,n′-Z. The latter controls the concentration of the reactive Pd0(PPh3) 2 and, consequently, also controls the rate of the overall oxidative addition with phenyl iodide. The more electron donating the Z group, the lower the affinity of dba-4,4′-Z for Pd0(PPh3) 2. As a result, the overall rate of the oxidative addition with Phi is faster when Z is an electron-donating group. For a given Z, the overall oxidative addition is faster when using Pd02(dba-n,n′-Z) 3 instead of Pd0(dba-n,n′-Z)2. Therefore, the rate of the oxidative addition can be modulated by changing the electronic properties of the dba ligands determined by substituents on its phenyl groups and by changing the structure of the precursors: P02 (dba-n,n′-Z)3 versus Pd0(dba-n,n′-Z) 2.
- Mace, Yohan,Kapdi, Anant R.,Fairlamb, Ian J. S.,Jutand, Anny
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p. 1795 - 1800
(2008/10/09)
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- Ferrocene-bridged Pd-NCN pincer complexes
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The meta-diaminoaryl ferrocene Fe[η5-C5 H4(NCNH)]2 [NCNH=1-C6H3 (CH2NMe2)2-3,5] (3) can be synthesised by the reaction of Fe[η5-C5H4(ZnCl)] 2 (1) with I-C6H3(CH2 NMe2)2-3,5 (2) in a 1:2 molar ratio in the presence of catalytic amounts of [Pd(PPh3)2]. The two meta-dimaminoaryl NCNH pincer units in 3 can be used to assemble multimetallic complexes. Thus, 3 produces on reaction with t BuLi and (Me2S)2PdCl2 trimetallic Fe[η5-C5H4(NCN-4-PdCl)]2 {NCN=1-C6H2(CH2NMe2) 2-3,5} (6) along with heterobimetallic Fe[η5 -C5H4(NCNH)][η5-C5 H4(NCN-4-PdCl)] (5). Complex 6 contains two bis-ortho-chelated pincer NCN-PdCl units, whereas 5 possesses one bis- ortho -chelated NCN pincer entity and one non-metallated NCNH moiety. Complex 6 is the first example in organometallic chemistry in which two bis-ortho-chelated diaminoaryl palladium units are bridged via the respective para C-atoms spanned by a redox-active ferrocenyl building block.
- K?cher, Stefan,van Klink, Gerard P.M.,van Koten, Gerard,Lang, Heinrich
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p. 230 - 234
(2007/10/03)
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- Mechanism of the Stille reaction catalyzed by palladium ligated to arsine ligand: PhPdl(AsPh3)(DMF) is the species reacting with vinylstannane in DMF
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The kinetics of the reaction of PhPdI(AsPh3)2 (formed via the fast oxidative addition of Phl with Pd0(AsPh3)2) with a vinyl stannane CH2=CH-Sn(n-Bu)3 has been investigated in DMF. This reaction (usually called transmetalation step) is the prototype of the rate determining second step of the catalytic cycle of Stille reactions. It is established here that the transmetalation proceeds through PhPdI(AsPh3)(DMF), generated by the dissociation of one ligand AsPh3 from PhPdI(AsPh3)2. PhPdI(AsPh3)(DMF) is the reactive species, which leads to styrene through its reaction with CH2=CH-SnBu3. Consequently, in DMF, the overall nucleophilic attack mainly proceeds via a mechanism involving PhPdI(AsPh3)(DMF) as the central reactive complex and not PhPdI(AsPh3)2. The dimer [Ph2Pd2(μ2-I)2 (AsPh3)2] has been independently synthesized and characterized by its X-ray structure. In DMF, this dimer dissociates quantitatively into PhPdI(AsPh3)(DMF), which reacts with CH2=CH-SnBu3. The rate constant for the reaction of PhPdI-(AsPh3)(DMF) with CH2=CH-SnBu3 has been determined in DMF for each situation and was found to be comparable.
- Amatore, Christian,Bahsoun, Ali A.,Jutand, Anny,Meyer, Gilbert,Ndedi Ntepe, Alexandre,Ricard, Louis
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p. 4212 - 4222
(2007/10/03)
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- Mechanism of the stille reaction. 2. Couplings of aryl triflates with vinyltributyltin. Observation of intermediates. A more comprehensive scheme
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The mechanism of the [PdL4]-catalyzed couplings between R-OTf (R = pentahalophenyl; L = PPh3, AsPh3) and Sn(CH = CH2)Bu3 has been studied. The addition of LiCl favors the coupling for L = AsPh3 in THF but retards it for L = PPh3. Separate experiments show that for L = AsPh3, LiCl accelerates the otherwise very slow and rate-determining oxidative addition of the aryl triflate to [PdL4], leading to trans-[PdRClL2]. Therefore, the overall process is accelerated. For L = PPh3, the rate-determining step is the transmetalation. Complex trans-[PdRXL2], with X = Cl, is formed in the presence of LiCl, whereas an equilibrium mixture mainly involving species with X = TfO, L, or S (S = solvent) is established in the absence of LiCl. Since the transmetalation is slower for X = Cl than for the other complexes, the overall process is retarded by addition of LiCl. The transmetalation in complexes trans-[PdRXL2], with X = Cl, follows the S(E)2(cyclic) mechanism proposed in Part 1 (Casado, A. L.; Espinet, P. J. Am. Chem. Soc. 1998, 120, 8978-8985), giving the coupling product R-CH=CH2'directly. For X = TfO or L, rather stable intermediates trans-[PdR(CH=CH2)L2] are detected, supporting an S(E)2(open) mechanism. The key intermediates undergoing transmetalation in the conditions and solvents most commonly used in the literature have been identified. The operation of S(E)2(cyclic) and S(E)2(open) pathways emphasizes common aspects of the Stille reaction with the Hiyama reaction where, using R2SiF3 that is chiral at the α-carbon of R2, retention or inversion at the transmetalated chiral carbon can be induced. This helps us to understand the contradictory stereochemical outcomes in the literature for Stille couplings using R2SnR3 derivatives that are chiral at the α-carbon of R2 and suggests that stereocontrol of the Stille reaction might be achieved.
- Casado,Espinet,Gallego
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p. 11771 - 11782
(2007/10/03)
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- 1,6-Diene complexes of palladium(0) and platinum(0): Highly reactive sources for the naked metals and [L-M0] fragments
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The complexes (cod)MCl2 (M = Pd, Pt; cod = cis,cis-1,5-cyclooctadiene) react with Li2(cot) (cot = cyclooctatetraene) in a 1,6-diene/diethyl ether mixture (1,6-diene = hepta-1,6-diene, diallyl ether, dvds (1,3-divinyl- 1,1,3,3-tetramethyldisiloxane)) to afford the isolated homoleptic dinuclear Pd0 and Pt0 compounds Pd2(C7H12)3 (1), Pd2(C6H10O)3·C6H10O (2'; 2: Pd2(C6H10O)3), Pd2(dvds)3 (3), and Pt2(C7H12)3 (4). When 1-4 are treated with additional 1,6-diene the equally homoleptic but mononuclear derivatives of type M(1,6-diene)2 (5-8) and with ethene the mixed alkene complexes (C2H4)M(1,6-diene) (9-12) are obtained in solution. Complexes 1-12 react with donor ligands such as phosphanes, phosphites, or (t)BuNC to give isolated complexes of types L-M(1,6-diene) (13-41), which have also been prepared by other routes. In all complexes the metal centers are TP-3 coordinated: complexes 1-4 contain chelating and bridging 1,6-diene ligands, whereas the other complexes contain a chelating 1,6-diene ligand and an η2-alkene (5-12) or η1-donor ligand (13-41). Of the studied 1,6-diene complexes the hepta-1,6-diene derivatives are most reactive, while the diallyl ether complexes are often more convenient to handle. The readily isolable dinuclear hepta-1,6-diene and diallyl ether complexes 1, 2', and 4, and their mononuclear pure olefin derivatives are among the most reactive sources for naked Pd0 and Pt0. The corresponding L-M(1,6-diene) complexes are equally reactive precursor compounds for the generation of [L-M0] fragments in solution, which for M =Pd are available otherwise only with difficulty. The results are significant for the operation of naked Pd0 and L-Pd0 catalysts in homogeneous catalysis.
- Krause, Jochen,Cestaric, Günter,Haack, Karl-Josef,Seevogel, Klaus,Storm, Werner,P?rschke, Klaus-Richard
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p. 9807 - 9823
(2007/10/03)
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- Exploration of the Stille coupling reaction for the syntheses of functional polymers
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The palladium-catalyzed Stille coupling reaction was used for preparing functionalized, conjugated polymers. This reaction has several advantages, two of which are that it requires mild reaction conditions and produces high yields. Several factors which affect the polymerization processes were investigated, such as the catalyst composition and concentration, different solvents and ligands, and structures of monomers. It was found that solvents that could keep the macromolecules in solution and stabilize the palladium(0) catalyst would yield polymers with high molecular weights. If a Pd(II) compound was used as the catalyst, a stoichiometric adjustment of the distannyl monomer was necessary to enhance the molecular weight of the resulting polymer. In general, it was found that a combination of an electron-rich distannyl monomer and an electron-deficient dihalide (ditriflate) monomer forms polymers with relatively high molecular weights. To further demonstrate the versatility of the Stille reaction for polycondensations, different types of conjugated polymers with different properties and applications, such as liquid crystalline conjugated polymers and conjugated photorefractive polymers, were synthesized.
- Bao, Zhenan,Chan, Wai Kin,Yu, Luping
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p. 12426 - 12435
(2007/10/03)
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- Indirect formation of carboxylic acids via anhydrides in the palladium-catalyzed hydroxycarbonylation of aromatic halides
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The carbonylation of [(Ph3P)2Pd2Ph2(μ-OH)2] (2) in the presence of PhI results in the quantitative formation of benzoic anhydride and [(Ph3P)2Pd2(PhCO)2(μ-I) 2] (3). This transformation contributes to some extent to the production of benzoic acid from haloarenes, CO, and alkali, catalyzed by [(Ph3P)2PdCl2], the latter being converted to 2 under the reaction conditions. Phenyl- and benzoylpalladium benzoates are likely key intermediates in the indirect formation of the acid, via the anhydride, by the carbonylation of 2. One such complex, [L2Pd(Ph)(PhCOO)] (5, L = Cy3P), was isolated from the carbonylation of [(Cy3P)2Pd2Ph2(μ-OH)2] (4) in hexane. The related complexes, [L2Pd2Ph2(μ-PhCOO)2] (6, L = PPh3; 7,L = PCy3), were prepared from benzoic acid and hydroxo complexes 2 and 4, respectively. Treatment of 6 and 7 with the corresponding phosphine afforded [L2Pd(Ph)(PhCOO)] (8, L = PPh3; 5,L = PCy3). When 6-8 were reacted with CO in benzene, benzoic anhydride was readily formed, whereas in the case of 5 both carbonylation and reductive elimination were sluggish. Crystallographic data for 6 (1:2 chloroform solvate): space group Pccn, a = 22.499(4) A?, b = 10.992(3) A?, c = 24.514(6) A?, V = 6062.4(23) A?3, Z = 4, R = 0.056, and Rw = 0.038.
- Grushin, Vladimir V.,Alper, Howard
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p. 4305 - 4315
(2007/10/02)
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- Fluoride-induced reduction of palladium(II) and platinum(II) phosphine complexes
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A novel redox reaction involving fluoride and phosphine complexes of palladium(II) is reported. The scope of this reaction has been investigated using the ligands PPh3, Ph2P(CH2)nPPh2 (n = 1-4), Ph2PCH2C(CH3)2CH2PPh 2, Ph2PCH3, and P(CH2CH2CN)3; several solvents including DMSO, pyridine, acetonitrile, and THF; and either n-Bu4NF·3H2O or KF/18-crown-6 as the fluoride source. The reduction products are palladium(0) phosphine complexes for which this reaction offers a convenient synthetic route. 31P and 19F NMR spectra permitted identification of the initial oxidation products as difluorophosphoranes (R3PF2), which subsequently hydrolyzed, forming phosphine oxides if a hydrated fluoride source is used. Results implicating a fluoride-induced redox reaction in the thermal decomposition of [(Ph3P)3PdCl]BF4 to yield [Pd3Cl(PPh2)2(PPh3) 3]BF4 are also presented. Preliminary results indicate that platinum complexes also undergo this reaction, but nickel complexes yield NiF2. The X-ray parameters for Pd(dppp)2 (dppp = 1,3-bis(diphenyphosphino)propane) are: monoclinic, space group C2/c (No. 15), a = 18.396 (2) A?, b = 13.290 (1) A?, c = 20.186 (2) A?, β = 109.383 (5)°, and Z = 4.
- Mason,Verkade
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p. 2212 - 2220
(2008/10/08)
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- Biphenyl-bridged metallocenes that are chiral, configurationally stable, and free of diastereomers
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Formation of diastereomers is precluded when biphenyl-bridged bis(cyclopentadienyls) and transition-metal halides combine to give chiral ansa-metallocenes. These cyclopentadienyls must be symmetrically substituted. Syntheses and X-ray diffraction analyses are reported for four biphenyl-bridged ansa-metallocenes: titanocene dichlorides 17 and 22, zirconocene dichloride 18, and ferrocene 13.
- Huttenloch, Monika E.,Diebold, Josef,Rief, Ursula,Brintzinger, Hans H.,Gilbert, Adam M.,Katz, Thomas J.
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p. 3600 - 3607
(2008/10/08)
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- Stabilization of bis(triphenylphosphine)palladium(0) by chloride ions. Electrochemical generation of highly reactive zerovalent palladium complexes
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"Pd0(PPh3)2" has been generated by electroreduction of Cl2Pd(PPh3)2 in the absence of PPh3.Its structure is consistent with xPd0(PPh3)2>nnx-, with values of x and/or n depending on the chloride ion
- Amatore, Christian,Azzabi, Mohamed,Jutand, Anny
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p. C41 - C54
(2007/10/02)
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- Intermediates in hydrosilylation of vinyltrichlorosilane catalyzed by palladium phosphine complexes
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Hydrosilylation of vinyltrichlorosilane by trichlorosilane in the presence of Pd(0) and Pd(II) phosphine complexes at 120°C leads to quantitative formation of 1,1-bis(trichlorosilyl)ethane (α-adduct), whereas this reaction with vinyltri(methyl, chloro)sil
- Marciniec
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- Preparation and reactions of bis(triphenylphosphine)palladium(0)
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The two-coordinate palladium complex, (Ph3P)2Pd, is succesfully prepared by the reaction of 3-allyl)Pd(PPh3)2>+ PF6- with Ph2MeSiLi.The complex has been characterized by Ir, 1H NMR, 13C NMR, 31P NMR, and UV spectroscopy
- Urata, Hisao,Suzuki, Hiroharu,Moro-oka, Yoshihiko,Ikawa, Tsuneo
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p. 235 - 244
(2007/10/02)
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