- Cycloneophylplatinum Chemistry: A New Route to Platinum(II) Complexes and the Mechanism and Selectivity of Protonolysis of Platinum-Carbon Bonds
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A new route to cycloneophylplatinum(II) complexes is reported and the selectivity of protonolysis of the platinum-aryl and -alkyl bonds has been determined. Reaction of [PtCl2(SMe2)2] with neophylmagnesium chloride gives the binuclear cycloneophylplatinum(II) complex [Pt2(CH2CMe2C6H4)2(μ-SMe2)2], 1, which is shown to exist as a mixture of syn and anti isomers. Complex 1 reacts reversibly with SMe2 to give [Pt(CH2CMe2C6H4)(SMe2)2], 2, and irreversibly with bidentate ligands NN = 3,4,7,8-tetramethyl-1,10-phenanthroline (phen?) or 4,4′-di-t-butyl-2,2'bipyridine (bubipy) to give the corresponding complexes [Pt(CH2CMe2C6H4)(phen?)], 3, and [Pt(CH2CMe2C6H4)(bubipy)], 4, respectively. Complex 2 reacts with HCl initially by cleavage of the aryl-platinum bond to give mostly trans-[PtCl(CH2CMe2Ph)(SMe2)2], which then rearranges to an equilibrium mixture with trans-[PtCl(C6H4-2-t-Bu)(SMe2)2], while 3 and 4 react to give [PtCl(CH2CMe2Ph)(phen?)] and [PtCl(CH2CMe2Ph)(bubipy)], which do not undergo the isomerization reaction. The protonolysis reactions occur by way of a platinum(IV) hydride complex in each case, and the unusual reactivity of complex 2 is attributed to the ease of dissociation of the Me2S ligands.
- Fard, Mahmood Azizpoor,Behnia, Ava,Puddephatt, Richard J.
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p. 3368 - 3377
(2018/10/02)
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- User-Friendly precatalyst for the methylation of polyfluoroaryl imines
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A readily accessible, user-friendly Pt(II) complex Cl 2Pt(SMe2)2,2) shows good reactivity for selective, catalytic methylation of polyfluoroarylimines.
- Buckley, Heather L.,Sun, Alex D.,Love, Jennifer A.
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p. 6622 - 6624
(2010/04/01)
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- NOVEL IRIDIUM-PLATINUM COMPLEX AND METHOD FOR PRODUCING SAME
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An iridium-platinum complex of the following formula: wherein Cp* is a pentamethylcyclopentadienyl ligand or the like, X is a hydrogen atom, or a substituent group such as a bromine atom or an organic group disposed at a position ortho, meta or para to the phenyl group, or at a combination of the positions, and Y is a methyl group or the like.
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Page/Page column 7
(2009/01/20)
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- Ligand binding energies in cationic platinum(II) complexes: A quantitative study in the gas phase
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Quantitative energy-resolved reactive cross-section measurements and DFT calculations are used to investigate the binding energies of various ligands to the metal center in cationic Pt(II) diimine complexes involved in C-H activation reactions. Independent synthesis of isomeric ions establishes the structure of the adducts formed in gas-phase reactions. The order and relative magnitude of a series of ligand binding energies extracted from experimental cross-sections reproduce the trends seen in solution-phase experiments only when the proper transition state model is employed in the deconvolution of the experimental crosssections. The choice of transition state model can be rationalized by qualitative structural arguments as well as quantum chemical calculations of the reaction coordinate for the dissociation of the range of possible ligands.
- Moret, Marc-Etienne,Chen, Peter
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p. 1523 - 1530
(2008/10/09)
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- Reactivity studies of trans-[PtClMe(SMe2)2] towards anionic and neutral ligand substitution processes
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Reaction of trans-[PtClMe(SMe2)2] with the mono anionic ligands azide, bromide, cyanide, iodide and thiocyanate result in substitution of the chloro ligand as the first step. In contrast the neutral ligands pyridine, 4-Me-pyridine and thiourea substitute a SMe2 ligand in the first step as confirmed by 1H NMR spectroscopy and the kinetic data. Detailed kinetic studies were performed in methanol as solvent by use of conventional stopped-flow spectrophotometry. All processes follow the usual two-term rate law for square-planar substitutions, kobs = k1 + k2[Y] (where k1 = kMeOH[MeOH]), with k1 = 0.088 ± 0.004 s-1 and k2 = 1.18 ± 0.13, 3.8 ± 0.3, 17.8 ± 1.3, 34.9 ± 1.4, 75.3 ± 1.1 mol-1 dm3 s-1 for Y- = N3, Br, CN, I and SCN respectively at 298 K. The reactions with the neutral ligands proceed without an appreciable intercept with k2 = 5.1 ± 0.3, 15.3 ± 1.8 and 195 ± 3 mol-1 dm3 s-1 for Y = pyridine, 4-Me-pyridine and thiourea, respectively, at 298 K. Activation parameters for MeOH, N3-, Br-, CN-, I-, SCN-, and Tu are ΔH≠ = 47.1 ± 1.6, 49.8 ± 0.6, 39 ± 3, 32 ± 8, 39 ± 5, 34 ± 4 and 31 ± 3 kJ mol-1 and ΔS≠ = -107 ± 5, -77 ± 2, -104 ± 9,-113 ± 28, -85 ± 18, -94 ± 14 and -97 ± 10 J K-1 mol-1, respectively. Recalculation of k1 to second-order units gives the following sequence of nucleophilicity: MeOH 3- - ~ py - - - 2)2] and SCN- follows the same rate law as stated above with k2 = 75.3 ± 1.1, 236 ± 4 and 442 ± 5 mol-1 dm3 s-1 for X- = Cl, I and N3, respectively, at 298 K. The corresponding activation parameters were determined as ΔH≠ = 34 ± 4, 32 ± 2 and 39.3 ± 1.7 kJ mol-1 and ΔS≠ = -94 ± 14, -86 ± 8 and -68 ± 6 J K-1 mol-1. All the kinetic measurements indicate the usual associate mode of activation for square planar substitution reactions as supported by large negative entropies of activation, a significant dependence of the reaction rate on different entering nucleophiles and a linear free energy relationship.
- Otto, Stefanus,Roodt, Andreas
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p. 4626 - 4632
(2007/10/03)
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- CHIRAL LIGANDS FOR ASYMMETRIC CATALYSIS
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The present invention provides transition metal complexes of enantiomerically enriched compounds for use as catalysts in asymmetric transformations.
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Page/Page column 40-41
(2010/02/15)
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- Bonding in cis- and trans-dichlorobis(dimethylsulfide)platinum(II) studied by vibrational (micro)spectroscopy and force field calculations
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The vibrational spectra of the square-planar complexes cis- and trans-dichlorobis(dimethylsulfide)platinum(II) have been investigated using Raman and synchrotron infrared microscopy of small samples, and mid- to far-infrared spectroscopy of macroscopic sa
- Glerup,Sorensen,Beichert,Johnson
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p. 129 - 139
(2007/10/03)
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- Reduction of (imine)Pt(IV) to (imine)Pt(II) complexes with carbonyl-stabilized phosphorus ylides
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A novel method is reported for generation of the difficult-to-obtain (imine)Pt(II) compounds that involves reduction of the corresponding readily available Pt(IV)-based imines by carbonyl-stabilized phosphorus ylides, Ph3P= CHCO2R, in nonaqueous media. The reaction between neutral (imino)Pt(IV) compounds [PtCl4{NH=C(Me)-ON=CR1R2}2] [R1R2 = Me2, (CH2)4, (CH2)5, (Me)C(Me)=NOH], [PtCl4{NH=C(Me)ONR2}2] (R = Me, Et, CH2Ph), [PtCl4{N=C(Me)O-N(R3)-C(R1) (R2)}2] (R1 = H; R2 = Ph or C6H4Me; R3 = Me) as well as anionic-type platinum(IV) complexes (Ph3PCH2Ph)[PtCl5{NH=C(Me) ON=CR2}] [R2 = Me2, (CH2)4, (CH2)5] and 1 equiv of Ph3P=CHCO2R (R = Me, Et) proceeds under mild conditions (ca. 4 h, room temperature) to give selectively the platinum(II) products (in good to excellent isolated yields) without further reduction of the platinum center. All thus prepared compounds (excluding previously described Δ4-1,2,4-oxadiazoline complexes) were characterized by elemental analyses, FAB mass spectrometry, IR and 1H, 13C{1H}, 31P(1H} and 195Pt NMR spectroscopies, and X-ray single-crystal diffractometry, the latter for [PtCl2{NH=C(Me)ON=CMe2}2] [crystal system tetragonal, space group P42/n (No. 86), a = b = 10.5050(10) A, c = 15.916(3) A] and (Ph3PCH2CO2-Me)[PtCl3(NCMe)] [crystal system orthorhombic, space group Pna21 (No. 33), a = 19.661(7) A, b = 12.486(4) A, c = 10.149(3) A]. The reaction is also extended to a variety of other Pt(II)/Pt(IV) couples, and the ylides Ph3P=CHCO2R are introduced as mild and selective reducing agents of wide applicability for the conversion of Pt(IV) to Pt(II) species in nonaqueous media, a route that is especially useful in the case of compounds that cannot be prepared directly from Pt(II) precursors, and for the generation of systematic series of Pt(II)/Pt(IV) complexes for biological studies.
- Wagner,Pakhomova,Bokach,Frausto da Silva,Vicente,Pombeiro,Kukushkin
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p. 1683 - 1689
(2008/10/08)
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- A New Procedure for Deoxygenation of Dimethyl Sulfoxide both Free and inPlatinum Complexes
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Under the action of N2H4*2HCl, the [Pt(Me2SO)2Cl4] complex is first reduced to [Pt(Me2SO)2Cl2], and than deoxygenation of inner-sphere Me2SO occurs to give the [Pt(Me2S)2Cl2] complex. The reaction of N2H4*2HCl with [H(Me2SO)]2[PtCl6] also results in formation of [Pt(Me2SO)Cl2]. Free Me2SO is converted to Me2S by the action of hydrazine chloride with a high yield. This reaction can be recommended for preparation of Me2S from Me2SO.
- Kukushkin, Yu. N.,Khromenkova, Z. A.,Esaulova, V. A.
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p. 1639 - 1641
(2008/10/08)
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- Stabilization of high oxidation states by rigid bidentate nitrogen ligands: Synthesis and characterization of diorgano- and triorganopalladium(IV) and cationic triorganoplatinum(IV) complexes
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Dimethylpalladium(II) and (di)methylplatinum(II) complexes containing the rigid bidentate nitrogen ligands bis(p-tolylimino)acenaphthene (pTol-BIAN) and bis(phenylimino)camphane (Ph-BIC) readily undergo oxidative addition of a variety of (organic) halides, to give the corresponding octahedral diorgano- and triorganopalladium(IV) and -platinum(IV) complexes. The palladium complexes PdMe2(R)X(NN) (RX = MeI, PhCH2Br; NN = pTol-BIAN, Ph-BIC) were synthesized and isolated at 20°C and were fully characterized. Reductive elimination from these complexes in chloroform obeyed first order kinetics and was slower than for other reported triorganopalladium(IV) complexes. The new diorganopalladium(IV) complexes PdMe2I2(NN), synthesized via oxidative addition of diiodine to PdMe2(NN) are much less stable than the triorganopalladium(IV) complexes studied. PtMe2(R)X(pTol-BIAN) (RX = MeI, PhCH2Br, EtI, PhCH(Me)Br, MeC(O)Cl, I2) and Pt(Me)I(R)X(pTol-BIAN) (RX = MeI, PhCH2Br, I2) were obtained via oxidative addition to PtMe2(pTol-BIAN) and Pt(Me)I(pTol-BIAN), respectively. Reaction of PtMe2(R)X(pTol-BIAN) with AgSO3CF3 led to the formation of remarkably stable five-coordinate [PtMe2(R)pTol-BIAN)]SO3CF3 complexes (R = Me, CH2-Ph, C(O)Me), which were fully characterized and can be isolated and kept at 20°C. The complexes are very stable toward reductive elimination, e.g. in CDCl3 and CD3CN [PtMe2(CH2-Ph)(pTol-BIAN)]SO3CF3 was stable for at least 7 days at 20°C or 40 h at 50°C. The analogous complex [PtMe2(CH2Ph)(phen)]SO3CF3 was also stable at 50°C in CD3CN for at least 40 h, whereas [PtMe2(CH2Ph)(pTol-DAB)]SO3CF3 gave 30-35% reductive elimination under these conditions. From the observed order of reductive elimination from Pd(IV) and Pt(IV) complexes the rigidity of the pTol-BIAN and Ph-BIC ligands appears to be the major factor in determining the stability of these complexes.
- Van Asselt, Rob,Rijnberg, Evelien,Elsevier, Cornelis J.
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p. 706 - 720
(2008/10/08)
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- PHENYLATION OF PLATINUM(II) THIOETHER COMPLEXES BY TETRAPHENYLBORATE(III) IN SOLID STATE AND NITROMETHANE SOLUTION
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Platinum(II) complexes of the type (1+) (thioether = dimethyl sulfide, thioxane) are capable of abstracting a phenyl group from the BPh4(1-) counterion with formation of trans- compounds.Thermal reactions proceed both in the solid phase and in nitromethane solution at elevated temperature and have preparative importance.Phenylation of the Pt(II) centre also occurs in reaction between and AgBPh4 in CH2Cl2 suspension.Brief X-ray crystallographic structural data for trans- and X (thioether = Me2S, tx, X=SO3CF3; thioether = Me2S, X=PF6) are reported. Key words: Platinum(II) thioether complexes; phenyl abstraction; tetraphenylborate ion; synthesis of thioether complexes; silver tetraphenylborate; X-ray structures.
- Kukushkin, Vadim Yu.,Loevqvist, Karin,Noren, Bertil,Oskarsson, Ake,Elding, Lars Ivar
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p. 253 - 256
(2007/10/02)
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- Studies of binuclear methyl and phenyl derivatives of platinum(II)
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Some reactions of the binuclear organoplatinum complexes , where R = Me or Ph are described, and a new synthetic method for the complex with R = Ph is reported.The dimethylsulphide ligands are easily displaced by other ligands, L, to give cis-.When R = Me, reaction with MeI and Ph2PCH2PPh2, dppm, gives 2(μ-dppm)>, whereas when R = Ph, reaction with MeI gives , which has been characterized as its adduct with 2,2'-bipyridine .The latter complex exists as a mixture of two isomers, though the reaction between and MeI initially gives only one isomer of , formed by trans-oxidative addition.The reaction of with hydrochloric acid yields a 1:1 mixture of and , and it is suggested that this reaction involves an intramolecular methyl group transfer between the platinum atoms of the dimer.
- Rashidi, Mehdi,Fakhroeian, Zahra,Puddephatt, Richard J.
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p. 261 - 267
(2007/10/02)
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- Kinetics of displacement of dimethyl sulfide from cis- and trans-dichlorobis(dimethyl sulfide)platinum(II) by heterocyclic amines in 1,2-dimethoxy ethane
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Second-order rate constants for the reactions cis- or trans-[Pt(Me2S)2Cl2] + am → cis- or trans-[Pt(Me2S)(am)Cl2] + Me2S (am = pyridine, 4-methylpyridine, 3,4-dimethylpyridine, 3,5-dimethylpyridine, 3-methylpyridine, 2,4-dimethylpyridine, 2-methylpyridine, 4-cyanopyridine, m-diazine, p-diazine) in 1,2-dimethoxyethane at 25°C are reported. The trans complexes are some 2.5 times more reactive than the cis isomers, but the dependence of the second-order rate constant on the amine basicity is the same in both cases: log k2 = 0.18pKa(amH+) + c. The results are compared with published data for the opening of a bis(thioether) chelate and with those for the analogous sulfoxide complexes. It is concluded that the bond breaking transition state contributes much less to the overall reactivity of the thioether complexes than it does to the reactivity of the corresponding sulfoxide species.
- Canovese, Luciano,Cattalini, Lucio,Marangoni, Giampaolo,Michelon, Gianni,Tobe, Martin L.
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p. 4166 - 4168
(2008/10/08)
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