- General route to halide-bridged organopalladium A-frame complexes and studies of reductive elimination from these bimetallic systems
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Reactions of [Pd2Cl2(μ-dppm)2] with RMgX (R = Me, Et, Bu, Ph, C6H4Me-4) at low temperature, followed by addition of CBr4 and excess NH4PF6 or 1 equiv of TIPF6, provided halide-bridged organopalladium A-frame complexes of the form [Pd2R2(μ-X)(μ-dppm)2]PF6. Mixed metal complexes were obtained similarly starting from [PdCtCl2(μ-dppm)2]. Unsymmetrical A-frames of the type [Pd2(C6H2Me3-2,4,6)R(μ-Cl)(μ-d ppm)2]+ were generated reaction of [Pd(C6H2Me3-2,4,6) (dppm)2]+ (obtained by treatment of [PdCl2 (cod)] w mesitylmagnesium bromide at low temperature, followed by 2 equiv of dppm) with [Pd2R2(μ-Cl)2 (AsPh3)2]. The organopalladium A-frames did not react readily with CO, but the corresponding acyl derivatives [Pd2(COR)2(μ-Cl)(μ-dppm)2]PF6 were produced by carbonylation of [Pd2R2(μ-Cl)2(AsPh3)2] followed by addition of dppm (R = Me, Et, Bn). Thermal decomposition of [Pd2(CH2Ph)2(μ-Cl)(μ-dppm)2]Cl was found to be first order in A-frame and resulted in quantitative formation of [Pd2Cl2(μ-dppm)2] and 1,2-diphenylethane. The methyl and aryl complexes underwent both reductive elimination and hydrogen abstraction reactions. [Pd2Et2(μ-Br)(μ-ddpm)2]PF6 decomposed by β-hydride elimination and subsequent reductive elimination to yield ethene and ethane, whereas the butyl derivative gave both 1- and 2-butene. Acetic acid was formed when [Pd2(COMe)2(μ-Cl)(μ-dppm)2]PF6 was heated in dmso-d6 solution, but decarbonylation was the predominant process in dioxane. The molecular structures of [Pd2(CH2Ph)2(μ-Br)(μ-dppm)2] PF6·H2O, 2C6H6 and [Pd2Cl2(μ-Cl)(μ-dppm)2]OH· 0.5(CH3)2CO are also described.
- Stockland Jr., Robert A.,Janka, Mesfin,Hoel, Gretchen R.,Rath, Nigam P.,Anderson, Gordon K.
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p. 5212 - 5219
(2008/10/08)
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- Synthesis and electrospray mass spectrometry of palladium(II) diphosphine complexes from oxidative addition of 2-bromopyridine to Pd0
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Oxidative addition reactions of palladium(0) phosphine complexes with 2-bromopyridine gave rise to a series of structurally distinctive complexes, namely trans-(N,P)-[Pd2Br2(PPh3) 2(μ-C5H4N-C2,N)2] 1, [Pd2(μ-C5H4N-C2,N) 2-(μ-dppm)2]Br2 2, [Pd2(η1-dppp)2-(μ-C5H 4N-C2,N)2(μ-dppp)]Br2 3, trans-[{PdBr(η1-C5H4N-C 2)(μ-dppb)}n] 4, trans-(N,P)-[Pd2Br2(μ-C5H 4N-C2,N)2(μ-dppb)] 5 and cis-[PdBr(η1-C5H4NH-C 2)(η2-dppf)]Br 6 [Ph2P(CH2)nPPh2, n = 1(dppm), 3(dppp) or 4(dppb); dppf= Fe(Ph2PC5H4)2]. Similarly, trans-(N,P)-[Pd2Cl2(μ-C9H 6N-C2,N)2(μ-dppb)] 7 has been obtained from 2-chloroquinoline and [Pd(dppb)2]. An array of structural possibilities is envisaged based on the different co-ordination modes of the pyridine (C or/and N bonded; terminal or bridging; pyridyl, pyridine or pyridinium), phosphine (terminal, bridging or chelating) bromide (terminal or ionised) ligands. Complexes 2 and 3, but not the others, can be obtained from phosphine exchange reactions of 1. Complexes 5 and 6 were analysed by X-ray single-crystal crystallographic methods. The former reveals a dinuclear structure with a dppb ligand bridging diagonally two metals that are juxtaposed by two syn-bridging pyridyl groups. It represents an unusual dinuclear core stabilised by two types of bridging ligands of contrasting steric and geometric demands. The latter shows a cationic and mononuclear square planar palladium(II) complex containing a chelating dppf, terminal bromide and an unusual C-bonded pyridyl group with the N-site protonated. The fragmentation of these complexes was investigated by electrospray mass spectrometry under different cone voltages. Breakdown of the dinuclear framework is facilitated by addition of H-Br to the N-Pd bonds of the bridging pyridyl group.
- Chin, Clavius C. H.,Yeo, Jeremy S. L.,Loh,Vittal,Henderson,Hor, T. S. Andy
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p. 3777 - 3784
(2007/10/03)
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- Reactions of [PdX2(dppm)] complexes with grignard reagents
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Reactions of [PdX2(dppm)] (X = Cl, Br) with a range of Grignard reagents have been investigated. Diorganopalladium complexes of the type [PdR2(dppm)] were obtained in good yield with the bulky mesityl or trimethylsilylmethyl groups,
- Stockland Jr., Robert A.,Anderson, Gordon K.,Rath, Nigam P.
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p. 5096 - 5101
(2008/10/08)
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- Photoreactions of Palladium Phosphine Complex with Chloroalkane. Production of Ethylene with 1,2-Dichloroethane and Novel Photochromic Behavior
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Photoirradiation on 02(dppm)3> (dppm = bis(diphenylphosphino)methane) in 1,2-dichloroethane solution with visible light yields I2Cl2(dppm)2> (2) and ethylene quantitatively.Irradiation of 2 in various solutions shows interesting photochromic behavior.
- Tsubomura, Taro,Itsuki, Atsushi,Homma, Masahiko,Sakai, Ken
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p. 661 - 664
(2007/10/02)
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- Di(phosphine)-bridged complexes of palladium. Parahydrogen-induced polarization in hydrogenation reactions and structure determination of tris(μ-bis(diphenylphosphino)methane)dipalladium, Pd2(dppm)3
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Reduction of Pd2Cl2(dppm)2 (dppm = bis(diphenylphosphino)methane) with excess NaBH4 produces a dark purple solid, I, which shows a reaction chemistry consistent with the stoichiometry Pd2Hx(dppm)2. Reaction of I with excess dppm produces the known compound Pd2(dppm)3. Crystals of Pd2(dppm)3 are monoclinic in space group P21/c with cell dimensions a = 14.733 (5) ?, b = 14.760 (5) ?, c = 29.720 (6) ?, and β = 97.44 (1)°. The structure of Pd2(dppm)3 is similar to that of the structurally characterized Pt2(dppm)3 analogue with approximate C3h symmetry. A total of 1 equiv of H2 and 1 equiv of methane is evolved per 3 Pd(dppm) units when I is treated with aqueous HCl and methyl iodide, respectively. The corresponding metal-containing products are Pd2Cl2(dppm)2 and a mixture of [Pd2I(CH3)(dppm)2]I and PdI2(dppm). The latter compound is also obtained upon oxidation of I with I2. Reaction of I with CH2I2 in dichloromethane yields a mixture of Pd2I2(μ-CH2)(dppm)2 and Pd2Cl2(μ-CH2)(dppm)2, while reaction with either Me3SiCl or Me2SiCl2 produces Pd2Cl2(dppm)2. Complex I is active in the catalytic hydrogenation of alkenes and alkynes. Parahydrogen-induced polarization (PHIP) is observed in the styrene product when solutions of I and phenylacetylene in CDCl3 are stored at -196°C under 3-4 atm of H2 for >8 h prior to reaction at 60-70°C. Similar results are obtained when para-enriched H2 is used without the storage time. Complex I decomposes upon heating in CDCl3 to mixtures of Pd2Cl2(dppm)2, PdCl2(dppm), and an unidentified red palladium compound. While this mixture is also active in hydrogenation and gives rise to PHIP, Pd2Cl2(dppm)2 by itself gives weak polarization under hydrogenation conditions and PdCl2(dppm) gives no polarization.
- Kirss, Rein U.,Eisenberg, Richard
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p. 3372 - 3378
(2008/10/08)
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- A route to trinuclear platinum-gold clusters
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New A-frame cluster complexes have been prepared by addition of electrophilic gold fragments to the Pt-Pt bond of , dppm = Ph2PCH2PPh2.For example, gave and gave NO3.The complexes reacted with to give BF4 when n = 1 or 2, but the bridged bis(A-frame) cluster complex 2CH2>(BF4)2 when n = 3.In contrast, CuCl reacted with to give .Attempts to synthesize A-frame clusters containing Pt2Ag, Pt2Cu, Pd2Au, or PdPtAu units were unsuccessful, and it is concluded that these units are considerably weaker than the analogous 3-center 2-electron bond of the Pt2Au unit.The AuCl unit is displaced from on reaction with diazomethane, with formation of .Key words: platinum, gold, cluster, copper, silver.
- Arsenault, G. J.,Puddephatt, R. J.
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p. 1800 - 1806
(2007/10/02)
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- Acid-catalysed Additions of Acetylenes to (X=Cl, Br, or I) to give Dimetallated Olefin Complexes of Type (R=H, Ph, or C6H4Me-p)
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The addition of acetylenes to (dppm=Ph2PCH2PPh2; X=Cl, Br, or I) is catalysed by traces of acid and (in some cases) methanol, giving (R=H, Ph, or C6H4Me-p) containig the dipalladated olefin ligand HC=CR.These r
- Higgins, Simon J.,Shaw, Bernard L.
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p. 457 - 460
(2007/10/02)
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- Synthesis and Reactions of Dinuclear Palladium Complexes Containing Methyls and Hydride on Adjacent Palladium Centers: Reductive Elimination and Carbonylation Reactions
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The transmetalation reaction of trimethylaluminum with the palladium chloride dimer Pd2Cl2(μ-dppm)2 (1) (dppm = bis(diphenylphosphino)methane) at -78 deg C gave an intermediate, Pd2ClMe(μ-dppm)2 (2), which disproportionated at ca. 10 deg C to yield the trans-face-to-face palladium dimer Pd2Cl2Me2(μ-dppm)2 (3) and a palladium dimer Pd2Cl2(μ-CH2)(μ-dppm)2 (5).The use of excess trimethylaluminum at -40 deg C gave the dimethyl complex, Pd2Me2(μ-dppm)2 (7).When 2 and 7 were protonated, a stable A-frame chloro-bridged dimer + (6) and a hydride-bidged dimer + (8) were obtained.Warming 6 in solution to ambient temperature caused the reductive elimination of methane; 8 lost methane and ethane at ambient temperatures.Both reductive eliminations were strictly intramolecular as determined by crossover experiments.The reaction of 6 with CO (1 atm) at -20 deg C first gave a carbonyl-bridged complex + (10) that rearranged to the acyl complex + (11) and then on warming eliminated acetaldehyde.The carbonylation of 8 (1 atm) proceeded stepwise to give first the mono- and then the diacyl complexes.The diacyl complex + (13) underwent the reductive elimination of acetaldehyde at ambient temperatures.
- Young, S. J.,Kellenberger, B.,Reibenspies, Joseph H.,Himmel, S. E.,Manning, M.,et al.
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p. 5744 - 5753
(2007/10/02)
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- The Synthesis and Reactions of Palladium-Iron Carbonyl Complexes containing Bridging Ph2PCH2PPh2 Ligands
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Treatment of tetrahydrofuran solution of FeI2 with two equivalents of Ph2PCH2PPh2 (dppm),under an atmosphere of CO, gave trans,mer-2(CO)(dppm-PP')(dppm-P)> (1b) in high yield.The bromide analogue
- Jacobsen, Grant B.,Shaw, Bernard L.
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p. 2005 - 2008
(2007/10/02)
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- Reaction of hydrogen sulfide with dinuclear palladium(I) complexes containing bis(diphenylphosphino)methane (dpm) and conversion of bridged-sulfide derivatives to bridged-sulfoxide species. X-ray crystal structure of the dimetallic sulfoxide Pd2Cl2(μ-SO)(μ-dpm)2, containing pyramidal sulfur
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Hydrogen sulfide reacts with the complexes Pd2X2(μ-dpm)2 (1) and the mixed-ligand complex Pd2Cl2(μ-dpm)(μ-dpmMe) under ambient conditions to yield quantitatively H2 and the corresponding A-frame, bridged-sulfide complexes such as Pd2X2(μ-S)(μ-dpm)2 [X = Cl, Br, I; dpm = bis(diphenylphosphino)methane, dpmMe = 1,1-bis(diphenylphosphino)ethane]. The sulfide complexes can be oxidized by using m-chloroperbenzoic acid or H2O2 to the corresponding μ-SO2 derivatives via intermediate bridged-sulfoxide (μ-SO) species. The complex Pd2Cl2(μ-SO)(μ-dpm)2, in which SO acts as a 2-electron donor, with the bonding at S being pyramidal, crystallizes in the tetragonal space group P43 with a = b = 21.214 (1) A?, c = 14.457 (1) A?, and Z = 4; the data were refined to R = 0.069 on the basis of 2452 reflections with I ≥ 2.5σ(I). Two detected isomers of Pd2Cl2(μ-SO)(μ-dpm)(μ-dpmMe) appear to result from differing orientations of the oxygen at the pyramidal sulfur atom. The spontaneous loss of SO2 from the μ-SO2 species regenerates 1 and allows for the two-stage, catalytic process: H2S + 2"O" → H2 + SO2. Mechanistic aspects of the reaction of H2S with Pd2Cl2(μ-dpm)2 are briefly discussed. The complex PdCl2(dpm) reacts with H2S under basic conditions to give Pd2(SH)2(μ-S)(μ-dpm)2.
- Besenyei, Gabor,Lee, Chung-Li,Gulinski, Jacek,Rettig, Steven J.,James, Brian R.,Nelson, David A.,Lilga, Michael A.
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p. 3622 - 3628
(2008/10/08)
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- The Extremely Rapid Acid-catalysed Additions of Acetylenes to and the Synthesis of
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The addition of acetylenes such as HCCH, HCCPh, or MeOOCCCCOOMe to to give 'dimetallated olefins' is catalysed by traces of acid or methanol but inhibited by a base: the 'dimetallated olefin' complex makes an interesting comparison with the vinylidene complex .
- Higgins, Simon J.,Shaw, Bernard L.
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p. 1629 - 1630
(2007/10/02)
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- Synthesis and characterization of dinuclear palladium(I) and mononuclear palladium(II) complexes containing 1,1-bis(diphenylphosphino)ethane (dpmMe) and related mixed-ligand complexes containing dpmMe with either bis(diphenylphosphino)methane (dpm) or 2-(diphenylphosphino)pyridine (Ph2Ppy). X-ray crystal structures of PdCl2(dpmMe) and Pd ...
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Full title: Synthesis and characterization of dinuclear palladium(I) and mononuclear palladium(II) complexes containing 1,1-bis(diphenylphosphino)ethane (dpmMe) and related mixed-ligand complexes containing dpmMe with either bis(diphenylphosphino)methane (dpm) or 2-(diphenylphosphino)pyridine (Ph2Ppy). X-ray crystal structures of PdCl2(dpmMe) and Pd2Cl2(μ-dpmMe)2. 1,1-Bis(diphenylphosphino) ethane (dpmMe) has been synthesized by treating 1,1-dichloroethane with 2 equiv of LiPPh2. Alkylation of bis(diphenylphosphino)methane (dpm) using n-BuLi and MeI occurs at the methylene carbon and one phosphorus atom to give the phosphonium salt [Ph2PCH(Me)P(Me)Ph2]I, which can be formed also by reaction of CH3I with dpmMe. The complex PdCl2(dpmMe) was prepared from PdCl2(PhCN)2, while Pd2X2(μ-dmMe)2 (X = Cl, Br, I, NCO), Pd2Cl2(μ-dpmMe)(μ-Ph2Ppy), and Pd2Cl2(μ-dpmMe)(μ-dpm) were prepared via ligand substitution of Pd2Cl2(μ-Ph2Ppy)2 with the appropriate bidentate ligand [Ph2Ppy = 2-(diphenylphosphino)pyridine]. The Pd2Cl2(μ-dpmMe)2 complex crystallized as the anti form in the orthorhombic space group Fdd2 with a = 22.249 (1) A?, b = 65.811 (5) A?, c = 12.833 (1) A? and Z = 16; the data were refined to R = 0.039 on the basis of 4470 reflections with I ≥ 3σ(I). A crystal of PdCl2(dpmMe) was triclinic of space group P1 with a = 14.547 (3) A?, b = 19.521 (5) A?, c = 9.788 (3) A? α = 103.60 (1)°, β = 108.34 (1)°, γ = 91.89 (2)°, and Z = 4 (two independent molecules); R = 0.026 from 7123 observed reflections with I ≥ 3σ(I). Of the dinuclear Pd2Cl2 species, only Pd2Cl2(μ-dpmMe)(μ-dpm) reacted with CO in solution to form reversibly the A-frame complex in which the gas has inserted into the metal-metal bond. The solid-state structure of Pd2Cl2(μ-dpmMe)2 shows that rotation of phenyl groups is somewhat inhibited by the presence of the methyl groups, but in solution rotation occurs, as evidenced by NMR data; lack of reactivity toward CO is attributed to a steric problem that would result from the required presence of one methyl group inside a boat ring conformation within a bridged carbonyl product.
- Lee, Chung-Li,Yang, Ye-Ping,Rettig, Steven J.,James, Brian R.,Nelson, David A.,Lilga, Michael A.
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p. 2220 - 2228
(2008/10/08)
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- Quantitative Recovery of Dihydrogen from Hydrogen Sulphide using the Complexes,
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The complexes (1) abstract sulphur from H2S under ambient conditions to form (2) and H2 quantitatively; (2) can be oxidized in stages to μ-SO and μ-SO2 derivative
- Lee, Chung-Li,Besenyei, Gabor,James, Brian R.,Nelson, David A.,Lilga, Michael A.
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p. 1175 - 1176
(2007/10/02)
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- Synthesis and Reactions of the Heterobimetallic Complex
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New methods of preparing (1b) (dppm = Ph2PCH2PPh2) are described, such as reduction of with zinc dust, formic acid, or hydrazine.Treatment of 3-allyl)2> with an excess of dppm gives pure (1b) readily, albeit in only 45 percent yield. 3-C3H5)ClPd(μ-dppm)PdCl(η3-C3H5)> is also described.The best route to (1b) is to treat and dppm with giving yields of 80-90 percent.Similar treatment of and dppm with t)2> gives (1a), often contaminated, however, with ca. 10 percent of .Treatment of dppm and with t)2> gives the previously unknown heterobimetallic complex (1c) in excellent yield (83-92 percent) and purity.The corresponding dibromide, di-iodide, and dithiocyanate were prepared from (1c) by metathesis.Complex (1c) readily reacts with some small molecules, SO2, CO, MeO2CCCCO2Me or CS2, to give 'A-frames' , , , and respectively.The addition of SO2, CO, or CS2 is reversible and SO2 promotes or catalyses the displacement of CO.Hydrogen-1, 31P-, and 195Pt n.m.r. data are given and discussed as are some i.r. data.
- Pringle, Paul G.,Shaw, Bernard L.
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p. 889 - 896
(2007/10/02)
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- Mixed Palladium-Platinum Complexes with Ph2PCH2PPh2 (dppm)
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The first mixed palladium-platinum complexes with dppm, together with their A-frame adducts with CO, SO2, and MeOOCC=-CCOOMe, are described.
- Pringle, Paul G.,Shaw, Bernard L.
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