- Towards a catalytic hydrogenolysis of silicon-silicon bonds: Formation of Si-H bonds from disilanes and H2 at platinum
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Reactions of the disilanes Cl2MeSiSiMeCl2, ClMe 2SiSiMe2Cl and Me3SiSiMe3 led to the products of oxidative addition cis-[Pt(SiMeCl2)2(PEt 3)2] (2
- Roscher, Anja,Bockholt, Andreas,Braun, Thomas
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p. 1378 - 1382
(2009/06/06)
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- Synthetic and reactivity studies of some asymmetric dinuclear platinum(II) monohydrido-bridged cations. The neutron diffraction structure of [(PEt3)2(Ph)Pt(μ-H)PtH(PEt3)2] [BPh4]
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The complexes [(PEt3)2(Ar)Pt(μ-H)PtH(PEt3)2] [BPh4] (Ar = Ph, 2,4-Me2C6H3, 2,4,6-Me3C6H2) were prepared and characterized. Multinuclea
- Albinati, Alberto,Bracher, Gustav,Carmona, Daniel,Jans, Josef H.P.,Klooster, Wim T.,Koetzle, Thomas F.,Macchioni, Alceo,Ricci, John S.,Thouvenot, René,Venanzi, Luigi M.
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p. 255 - 265
(2008/10/08)
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- Equilibria of the thiametallacycles with tris(triethylphosphine)platinum(0) and dibenzothiophene, benzothiophene, or thiophene: The hydrodesulfurization reaction
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The thiaplatinacycles, [(PtSC12H8)(PEt3)2], 1, [(PtSC8H6)(PEt3)2], 2, and [(PtSC4H4)(PEt3)2], 3, in which Pt(PEt3)2 has inserted into one C-S bond of dibenzothiophene (DBT), benzothiophene (BT), and thiophene (T), respectively, are formed by the reversible reaction of tris(triethylphosphine)platinum(0) with the thiophene. The structure of complex [(PtSC8H6)(PEt3)2] (2) was confirmed by an X-ray determination that showed a square-planar Pt(II) bound to two cis PEt3 ligands, and to the S and the CH=, in a six-membered Pt-S-C-C-C-C ring [Pt-S(1), 2.315(5) ?; Pt-C(4), 2.035(19) ?; Pt-P(1), 2.301(5) ?, trans to S(1); and Pt-P(2), 2.386(5) ?, trans to C(4); P(1)-Pt-P(2), 97.6(2)°; S(1)-Pt-P(2), 87.0(2)°; S(1)-Pt-C(4), 88.6(6)°; P(1)-Pt-C(4), 86.8(6)°]. The adducts 1 and 3, derived from DBT and T, have been shown to have similar structures spectroscopically. The free thiophenes and Pt(PEt3)3 are regenerated on heating complexes 1-3 with Et3P; [(PtSCaHb)(PEt3)2] + Et3P ? [Pt(Et3P)3] + SCaHb. Keqm = [Pt(Et3P)3][SCaHb]/[PtSCaH b)(PEt3)2][Et3P] and is 10 for 1 (DBT) and 3 (T) and 1 for 2 (BT) at 100 °C. The complexes 1-3 undergo a variety of cleavage reactions; thus, the Pt-C bond in 1 is cleaved by HCl to give 2-phenylthiophenol and [Pt(PEt3)2Cl2], and all three complexes are degraded by hydride reagents to give the completely desulfurized hydrocarbons: biphenyl from 1, styrene and ethylbenzene from 2, and butadiene and butenes from 3. When the reactions are carried out with Et3SiH as reducer, the complex [Pt(SH)(H)(PEt3)2] is identified among the products, together with [Pt(Et3Si)(H)(PEt3)2], The former is a coproduct of the desulfurization, while the latter arises from addition of Et3SiH to [Pt(PEt3)2] (from reversal of the formation of [(PtSCaHb))(PEt3)2]) and is accompanied by the formation of the free thiophene. Under comparable conditions, the amount of desulfurization decreases in the order BT complex 2 (73%) > DBT complex 1 (50%) > T complex 3 (ca. 4%). These hydride reactions show the novel feature that the C-S bond is cleaved as well as the Pt-C bond; possible mechanisms for the platinum and for the known nickel- and hydride-promoted hydrodesulfurization (HDS) reactions are discussed.
- Garcia, Juventino J.,Mann, Brian E.,Adams, Harry,Bailey, Neil A.,Maitlis, Peter M.
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p. 2179 - 2186
(2007/10/02)
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- Stability of (Chloromethyl)platinum(II) Complexes
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The stabilities of , (cod = cycloocta-1,5-diene) and a range of phosphine-containing mono- and cis-bis-(chloromethyl)platinum(II) complexes have been investigated in deuteriochloroform at room temperature.Some of the bis(chloromethyl) derivatives appear to be indefinitely stable (cod and chelating arylphosphines), others suffer very slow decomposition to the dichlorides (non-chelating arylphosphines), and the remainder decompose relatively rapidly, and cleanly, to the dichlorides plus ethylene (alkylphosphines, non-chelating faster than chelating).Rapid decomposition of the arylphosphine complexes can be induced by adding hexafluoroisopropyl alcohol to the deuteriochloroform solutions.Attempts to generate 2> by addition of P(C6H11)3 to resulted in the formation of cis--+(C6H11)3>Cl2>; a mechanism is proposed.All cis-mono(chloromethyl) derivatives studied appear to be indefinitely stable.In contrast, the trans-mono(chloromethyl) complexes, although stable in very dry solvent, undergo decomposition in the presence of moisture to the corresponding hydrides plus formaldehyde; a mechanism is proposed.The hydrides undergo subsequent conversion into a mixture of cis and trans dichlorides.
- McCrindle, Robert,Arsenault, Gilles J.,Gupta, Anuradha,Hampden-Smith, Mark J.,Rice, Richard E.,McAlees, Alan J.
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p. 949 - 954
(2007/10/02)
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- Kinetic study of β-hydride elimination of monoalkyl complexes of platinum(II): Effects of varying the alkyl chain length or the cis group in the reaction of cis-bis(triethylphosphine)(alkyl)(halo or pseudohalo)platinum(II) complexes
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The monoalkyl complexes cis-[Pt(PEt3)2(R)Br] (R = C2H5, C2D5, n-C3H7, n-C4H9) and cis-[Pt(PEt3)2(n-C4H9)X] (X = Cl, Br, I, NO2, N3, SCN, SeCN) undergo a facile β-hydride elimination in acetone, yielding trans-[Pt(PEt3)2HX] and olefins. No alkanes are produced in these reactions that go to completion and are unaffected by the presence of an excess of halide ion in solution that serves to prevent a possible concurrent geometrical isomerization. The corresponding trans-monoalkyl species are stable under the same experimental conditions. The systems were characterized by 1H and 31P NMR. The rates of thermal decomposition were obtained by GLC, measuring the relative amounts of volatile products at various times. The ethyl complex decomposes at a rate ten times slower than that of the n-propyl and n-butyl analogues. For the complexes cis-[Pt(PEt3)2(R)Br], the activation parameters are as follows: R = C2H5, ΔH? = 101 ± 2 kJ mol-1, ΔS? = +5 ± 4 J K-1 mol-1; R = n-C3H7, ΔH? = 91 ± 4 kJ mol-1, ΔS? = -7 ± 10 J K-1 mol-1; R = n-C4H9, ΔH? = 90 ± 2 kJ mol-1, ΔS? = -4 ± 4 J K-1 mol-1; R = C2D5, ΔH? = 99 ± 2 kJ mol-1, ΔS? = -10 ± 5 J K-1 mol-1. At 298.16 K, the kinetic isotope effect (kd(C2H5)/kd(C2D 5)) is 3.1. The rates of decomposition of the complexes cis-[Pt(PEt3)2(n-C4H9)X] are strongly dependent on the nature of the X group, the overall difference of reactivity being at least 4 orders of magnitude between the first and the last members of the series. The reactivity sequence X = N3 2 1H), δ(195Pt), and 1J(PtP)) of the trans-[Pt(PEt3)2HX] hydride products. The distribution of the olefin products, 1-butene, cis-2-butene, and trans-2-butene is also dependent on the nature of X. The most probable mechanism for the thermolysis involves fast and reversible β-hydride elimination and olefin insertion in a pre-rate-determining step, followed by slow olefin loss from a 5-coordinate [PtL2(H)(olefin)X] intermediate.
- Alibrandi, Giuseppe,Scolaro, Luigi Monsù,Minniti, Domenico,Romeo, Raffaello
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p. 3467 - 3472
(2008/10/08)
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- Electrochemical generation and reactivity of bis(tertiary phosphine)platinum(0) complexes: A comparison of the reactivity of [Pt(PPh3)2] and [Pt(PEt3)2] equivalents
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Electrochemical reduction of cis-[PtCl2(PR3)2] (R = Ph, Et) in CH3CN/C6H6 containing NBu4ClO4 at a Hg pool electrode generates [Pt(PR3)2] equivalents in solution. Where R = Ph, the [Pt(PR3)2] equivalent may be trapped by O2, O2/CO2, HCl, MeI, C6H5COCl, and RC≡CR (R = Ph, COOMe) but not by the less reactive substrate PhCl. Where R = Et, the [Pt(PR3)2] equivalent reacts with the NBu4+ cation to ultimately generate trans-[PtH(Cl)(PEt3)2]. Prolonged electrolyses cause reduction of trans-[PtH(Cl)(PEt3)2] leading to hydride attack on the CH3CN solvent and ultimately forming trans-[PtH(CH2CN)(PEt3)2]. In the presence of bases such as NBu3, trans-[PtH(CH2CN)(PEt3)2] is isomerized in CH3CN solution producing trans-[PtCN(CH3)(PEt3)2]. The use of electroinactive trapping agents such as PhCl or PhCN as cosolvents for the reduction of cis-[PtCl2(PEt3)2] allows trapping of the [Pt(PEt3)2] equivalents as trans-[PtPh-(X)(PEt3)2] (X = Cl, CN).
- Davies, Julian A.,Eagle, Cassandra T.,Otis, Deborah E.,Venkataraman, Uma
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p. 1080 - 1088
(2008/10/08)
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- Preparation and characterization of some mixed ligand complexes of platinum(II)
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The mixed ligand complexes PtX2(ER3)L and PtXY(ER3)L (where ER3 = PR3 or AsMe3; L = phosphine, arsine; X = Cl; Y = Cl, H or Me) have been prepared and characterized. Reaction of PtMe2(ER3)L with HCl yields PtMeCl(ER3)L, in exclusively one of three possible isomeric forms. Excess tetramethyltin reacts with Pt2Cl2(μ-Cl)2(PMe2Ph)2 giving both cis and trans Pt2(μ-Cl)2(PMe2Ph)2, as identified from the NMR spectra. Cleavage of Pt2(μ-Cl)2Me2(PMe2Ph)2 with donor ligands such as AsPh3, PMe2 or pyridine, was useful as a synthetic route to the unsymmetrical methylchloro PtII derivatives. The reaction of cis-[PtMe2(PPh3)(AsPh3)] with excess dimethylacetylenedicarboxylate (DMA) yielded only one product, which was of the formula trans-[Pt{C(COOCH3)C(COOCH3)CH3}2(PPh3)(AsPh3)], with the alkenyl groups having the same geometry about the CC bond. The use of diethylacetylene-dicarboxylate (DEA) rather than DMA gave a similar product. However, when cis-[PtMe2(PEt3)(AsPh3)] was allowed to react with DMA, two products of the formula trans-[Pt{C(COOCH3)C(COOCH3)CH3}2(PEt3)(AsPh3)] were obtained, with the stereochemistry of both alkenyl groups being either cis or trans.
- Clark, Howard C.,Goel, Anil B.,Jain, Vimal K.,Tyers, Kenneth G.,Wong, Chun S.
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p. 123 - 134
(2007/10/02)
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- Photochemical generation of bis(phosphine)palladium and bis(phosphine)platinum equivalents
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Ultraviolet irradiation of oxalato bis(tertiary phosphine) complexes of platinum(II) and palladium(II), Pt(C2O4)L2 and Pd(C2O4)L2, results in the reductive elimination of the oxalate ligand
- Paonessa, Ralph S.,Prignano, Andrea L.,Trogler, William C.
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p. 647 - 657
(2008/10/08)
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- SOME CHEMISTRY OF MIXED LIGAND COMPLEXES OF PLATINUM
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Simple synthetic routes to the mixed ligand complexes PtLL'X2 and PtLL'XY (L' = PEt3; L = phosphine, arsine, etc.; X = Cl and Y = Cl, H or Me) are described; unexpectedly, these display an extensive chemistry without disproportionation, although in some c
- Clark, Howard C.,Goel, Anil B.,Wong, Chun S.
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p. C101 - C104
(2007/10/02)
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