- Reaction of silafluorenes with (Ph3P) 2Pt(η2-C2H4): Generation and characterization of Pt-Si monomers, dimers and trimers
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The reaction of silafluorene (1; H2SiC12H 8) with (Ph3P)2Pt(η2-C 2H4) (2) at room temperature in C7D8 initially provided the mononuclear complex (Ph3P) 2Pt(H)[Si(H)C12H8] (3), followed by the appearance of the unsymmetrical dinuclear complex (Ph3P) 2(H)Pt(μ-SiC12H8)(μ-η2- HSiC12H8)Pt(PPh3) (4) and finally the novel trinuclear complex [(Ph3P)Pt(μ-SiC12H 8)]3 (5). The three complexes were characterized by multinuclear NMR spectroscopy and by X-ray crystallography (5). The molecular structure of 5 exhibits a nonplanar Pt3Si3 core. When the reaction was conducted at low temperature until the silafluorene was consumed and the mixture then warmed to room temperature, the dinuclear complex 4 could be isolated. The related substituted silafluorene system 3,7-di-tert- butylsilafluorene (6; H2SiC20H24) also reacted with 2 to provide both mono- and dinuclear complexes (7 and 8) analogous to 3 and 4. The dinuclear complex 8 was isolated and crystallographically characterized. Each of the two Pt centers in complex 8 exhibits a unique environment. In solution at low temperature 8 is best described as having one platinum center with a terminal hydride, [Pt(H)(PPh3)2], and the second platinum with a nonclassical [Si...H...Pt(PPh 3)] unit. However, in the solid state, the two hydrides may both adopt a bridging environment. Heating a sample of the unsymmetrical dimer 8 led to the formation of several products, one of which was the trimer 9, analogous to 5.
- Braddock-Wilking, Janet,Corey, Joyce Y.,Trankler, Kevin A.,Dill, Kimberly M.,French, Lisa M.,Rath, Nigam P.
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- Reactions of organotin(IV) compounds with platinum complexes. Part(III). Reactions of (R2Sn)n, (R = Me or Ph, n = 6; R = Et, n = 9) with platinum complexes
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The R2Sn moieties formed when the cyclic compounds (R2Sn)n, R = Me or Ph, n = 6; R = Et, n = 9, are exposed to light, react with the platinum(II) complexes [PtCl2L2], L = PEt3, PPr3, PBu3, PEtPh2, PPh3 to give new complexes of the general formula [PtCl(SnR2Cl)L2]. Similarly, Et2Sn from (Et2Sn)9 reacts with [PtMe(Cl)L2] to give [PtMe(SnEt2Cl)L2] and Ph2Sn from (Ph2Sn)6 reacts with [PtPh(Cl)L2] or [PtPh2L2] to give [PtPh(SnPh2Cl)L2] or [PtPh(SnPh3)L2] (L = PEt3), respectively. Reactions involving (R2Sn)n and the bridged complex [{Pt(μ-Cl)ClL}2] give a mixture of [PtCl(SnR2Cl)L2] and [PtCl(SnRCl2)L2], R = Me or Et, L = PBu3. It is suggested that these reactions initially involve insertion of R2Sn moieties into Pt-Cl bonds of the complexes [PtX(Cl) L2] or [{Pt(μ-Cl)ClL}2] then generate R2SnXCl (X = Cl, Me, Ph) and the Pt(0)complex [PtL2], which undergoes oxidative-addition of the formed tin(IV) species to give complexes containing Pt-Sn bonds. With (Ph2Sn)6 and [PtPh2L2], the mechanism takes a different course. Reactions under similar conditions involving the Pt(0) complexes [Pt(C2H4(PPh3)2] or [Pt(COD)2], (COD = 1,5-cyclooctadiene) and (R2Sn)6, R = Me or Ph, gave no detectable complexes containing Pt-Sn bonds. The complex [Pt(PEt3)4] and (MeSn)6 likewise gives no species containing Pt-Sn bonds but with (Ph2Sn)6, two complexes, tentatively identified as trans-[PtPh(Sn2Ph5)(PEt3)2] and trans-[PtPh(Sn6Ph11)(PEt3)2], were detected in the solution. In all cases, the products were identified by 31P-NMR spectroscopy.
- Al-Allaf, Talal A.K
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- Reactivity of o-Diphenylphosphinobenzaldehyde toward . X-Ray Structure of *C6H6
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The compound o-diphenylphosphinobenzaldehyde reacts with under mild conditions to give the acyl hydride .In the presence of butanol a complete decarbonylation of the aldehyde occurs with formation of .The X-ray crystal structure of the acyl complex has been determined.The crystals are orthorombic, space group Pn21a, with a = 17.673(9), b = 16.586(8), and c = 12.160(6) Angstroem.The structure has been solved by three-dimensional Patterson and Fourier syntheses and refined by least squares to final R and R' of 0.049 and 0.046 respectively.The metal atom is surrounded in a distored square-planar geometry by the acyl ligand, a triphenylphosphine and hydride ligand.
- Ghilardi, Carlo A.,Midollini, Stefano,Moneti, Simonetta,Orlandini, Annabella
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- Forging Unsupported Metal–Boryl Bonds with Icosahedral Carboranes
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In contrast to the plethora of metal-catalyzed cross-coupling methods available for the installation of functional groups on aromatic hydrocarbons, a comparable variety of methods are currently not available for icosahedral carboranes, which are boron-rich three-dimensional aromatic analogues of aryl groups. Part of this is due to the limited understanding of the elementary steps for cross-coupling involving carboranes. Here, we report our efforts in isolating metal-boryl complexes to further our understanding of one of these elementary steps, oxidative addition. Structurally characterized examples of group 10 M?B bonds featuring icosahedral carboranes are completely unknown. Use of mercurocarboranes as a reagent to deliver M?B bonds saw divergent reactivity for platinum and palladium, with a Pt?B bond being isolated for the former, and a rare Pd?Hg bond being formed for the latter.
- Saleh, Liban M. A.,Dziedzic, Rafal M.,Khan, Saeed I.,Spokoyny, Alexander M.
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- The Mechanism of Hydrogenolysis of Dineopentylbis(triethylphosphine)platinum(II)
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Dineopentylbis(triethylphosphine)platinum(II) reacts with H2 (34 psi) at 32 deg C in hydrocarbon solvents and yields neopentane and trans-dihydridobis(triethylphosphine)platinum(II).The addition of triethylphosphine (L) changes the rate-limiting step of the reaction.When = 0 M, the overall rate-limiting step is the dissociation of triethylphosphine from L2PtR2: no isotope effect is observed on substitution of D2 for H2, and the rate is independent of pressure of H2.When > 0.1M, phosphine loss is reversible,and a later step,either addition of H2 to platinum or (more probably) elimination of neopentane from platinum, is rate limiting: the rate of reaction depends on the first order of the H2 pressure, and an isotope effect of kH/kD ca. 1.9 is observed on substitution of H2 by D2.Activation parameters obtained at 0.0, 0.1 and 0.5 M triethylphosphine are presented.These data are useful in understanding the differences in rates of inter- and intramolecular oxidative additions to platinum(II).The rate of reaction of H2 with several structurally related bis(phosphine)dialkylplatinum(II) compounds was surveyed under similar reaction conditions.In general, bulky substituents on platinum accelerate the reaction.This observation suggests that phosphine dissociation is a general feature of reaction of bis(phosphine)dialkylplatinum(II) compounds with dihydrogen.
- Reamey, Robert H.,Whitesides, George M.
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- Hydrosilylation of aromatic aldehydes and ketones catalyzed by mono- and tri-nuclear platinum(0) complexes
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Hydrosilylation of aromatic aldehydes and acetophenone with H2SiPh2 was studied by using Pt complexes as the catalyst. Reaction of aromatic aldehydes, such as PhCHO, 4-FC6H4CHO, 4-MeC6H4CHO and 4-CF3C6H4CHO with H2SiPh2 in the presence of [Pt(PPh3)3] cata
- Tsuchido, Yoshitaka,Abe, Ryota,Kamono, Megumi,Tanaka, Kimiya,Tanabe, Makoto,Osakada, Kohtaro
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p. 858 - 864
(2018/05/23)
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- A new approach to light-gated Pt catalysts for the hydrosilylation
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A new concept for a light-gated transition metal catalyst is presented based on a photo-active moiety in the outer ligand sphere of the complex which on irradiation reacts irreversibly with some part of the inner ligand sphere releasing a free coordination site. The principle is exemplified on a platinum complex for the hydrosilylation. It is proven that the catalytic properties of the complex and the properties of the photo-gate can be fine-tuned on the chemical problem independently of each other.
- Buchner, Magnus R.,Bechlars, Bettina,Ruhland, Klaus
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- Mechanistic study of β-hydrogen elimination from organoplatinum(II) enolate complexes
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A detailed mechanistic investigation of the thermal reactions of a series of bisphosphine alkylplatinum(II) enolate complexes is reported. The reactions of methylplatinum enolate complexes in the presence of added phosphine form methane and either free or coordinated enone, depending on the steric properties of the enone. Kinetic studies were conducted to determine the relationship between the rates and mechanism of β-hydrogen elimination from enolate complexes and the rates and mechanism of β-hydrogen elimination from alkyl complexes. The rates of reactions of the enolate complexes were inversely dependent on the concentration of added phosphine, indicating that β-hydrogen elimination from the enolate complexes occurs after reversible dissociation of a phosphine. A normal, primary kinetic isotope effect was measured, and this effect was consistent with rate-limiting β-hydrogen elimination or C-H bond-forming reductive elimination to form methane. Reactions of substituted enolate complexes were also studied to determine the effect of the steric and electronic properties of the enolate complexes on the rates of β-hydrogen elimination. These studies showed that reactions of the alkylplatinum enolate complexes were retarded by electron-withdrawing substituents on the enolate and that reactions of enolate complexes possessing alkyl substituents at the β-position occurred at rates that were similar to those of complexes lacking alkyl substituents at this position. Despite the trend in electronic effects on the rates of reactions of enolate complexes and the substantial electronic differences between an enolate and an alkyl ligand, the rates of decomposition of the enolate complexes were similar to those of the analogous alkyl complexes. To the extent that the rates of reaction of the two types of complexes are different, those involving β-hydrogen elimination from the enolate ligand were faster. A difference between the rate-determining steps for decomposition of the two classes of complexes and an effect of stereochemistry on the selectivity for β-hydrogen elimination are possible origins of the observed phenomena.
- Alexanian, Erik J.,Hartwig, John F.
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supporting information; scheme or table
p. 15627 - 15635
(2009/03/12)
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- Expedient, direct synthesis of (L)Pt(0)(1,6-diene) complexes from H 2PtCl6
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The one-pot synthesis of useful [Pt2(0)(η4-1,6- diene)3] complexes, directly from H2PtCl 6·xH2O, has remained an unaddressed problem. We have found that the treatment of an i-PrOH solution of H2PtCl 6-XH2O by (Me3SiO)2MeSi(CH=CH 2), in the presence of allyl ether (AE), followed by reaction of the in situ generated Pt(O) species with IPr carbene (IPr =1,3-bis(2,6- diisopropylphenyl)imidazol-2-ylidene) enables the isolation of (IPr)Pt(AE) (I) in 50-70% yield. The scope of this method has been extended to other (L)Pt(1,6-diene) complexes (L = 1,3-dicyclohexylimidazol-2-ylidene, triphenylphoshine; 1,6-diene = diethyl 2,2-diallylmalonate (DAM)), and the molecular structure of the (IPr)Pt(DAM) (4) complex has been unequivocally determined by a single-crystal X-ray diffraction analysis. These results are significant for the formation of active L-Pt(O) fragments in catalysis.
- Berthon-Gelloz, Guillaume,Schumers, Jean-Marc,Lucaccioni, Fabio,Tinant, Bernard,Wouters, Johan,Marko, Istvan E.
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p. 5731 - 5734
(2008/10/09)
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- Distinct electronic effects on reductive eliminations of symmetrical and unsymmetrical bis-aryl platinum complexes
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Symmetrical bis-aryl platinum complexes (DPPF)Pt(C6H 4-4-R)2 (R = NMe2, OMe, CH3, H, Cl, CF3) and electronically unsymmetrical bis-aryl platinum complexes (DPPF)Pt(C6H4-R)(C6H4-4-X) (R = CH3, X = NMe2, OMe, H, Cl, F, CF3; R = OMe, X = NMe2, H, Cl, F, CF3; R = CF3, X = H, Cl, NMe2; and R = NMe2, X = H, Cl) were prepared, and the rates of reductive elimination of these complexes in the presence of excess PPh3 are reported. The platinum complexes reductively eliminated biaryl compounds in quantitative yields with first-order rate constants that were independent of the concentration of PPh3. Plots of Log(k obs/kobs(H)) vs Hammett substituent constants (σ) of the para substituents R and X showed that the rates of reductive elimination reactions depended on two different electronic properties. The reductive elimination from symmetrical bis-aryl platinum complexes occurred faster from complexes with more electron-donating para substituents R. However, reductive elimination from a series of electronically unsymmetrical bis-aryl complexes was not faster from complexes with the more electron-donating substituents. Instead, reductive elimination was faster from complexes with a larger difference in the electronic properties of the substituents on the two platinum-bound aryl groups. The two electronic effects can complement or cancel each other. Thus, this combination of electronic effects gives rise to complex, but now more interpretable, free energy relationships for reductive elimination.
- Shekhar, Shashank,Hartwig, John F.
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p. 13016 - 13027
(2007/10/03)
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- Elimination-addition mechanism for nucleophilic substitution reaction of cyclohexenyl iodonium salts and regioselectivity of nucleophilic addition to the cyclohexyne intermediate
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The reaction of 4-substituted cyclohex-1-enyl(phenyl)iodonium tetrafluoroborate with tetrabutyl-ammonium acetate gives both the ipso and cine acetate-substitution products in aprotic solvents. The isomeric 5-substituted iodonium salt also gives the same mixture of the isomeric acetate products. The reaction is best explained by an elimination-addition mechanism with 4-substituted cyclohexyne as a common intermediate. The cyclohexyne formation was confirmed by deuterium labeling and trapping to lead to [4 + 2] cycloadducts and a platinum-cyclohexyne complex. Cyclohexyne can also be generated in the presence of some other mild bases such as fluoride ion, alkoxides, and amines, though amines are less effective bases for the elimination. Kinetic deuterium isotope effects show that the anionic bases induce the E2 elimination (k H/kD > 2), while the amines allow formation of a cyclohexenyl cation in chloroform to lead to E1 as well as SN1 reactions (k H/kD ≈ 1). Bases are much less effective in methanol, and methoxide was the only base to efficiently afford the cyclohexyne intermediate. Nucleophiles react with the cyclohexyne to give regioisomeric products in the ratio dependent on the ring substituent. The observed regioselectivity of nucleophilic addition to substituted cyclohexynes is rationalized from calculated LUMO populations, which are governed by the bond angles at the acetylenic carbons: The less deformed carbon has a higher LUMO population and is preferentially attacked by the nucleophile.
- Fujita, Morifumi,Kim, Wan Hyeok,Sakanishi, Yuichi,Fujiwara, Koji,Hirayama, Sayaka,Okuyama, Tadashi,Ohki, Yasuhiro,Tatsumi, Kazuyuki,Yoshioka, Yasunori
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p. 7548 - 7558
(2007/10/03)
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- Intermolecular propargyl/allenyl group transfer from Pd(II) to Pt(0) and Pt(II) to Pd(0). Key reaction in metal-catalyzed isomerization between propargyl and allenyl metal complexes
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Isomerization of phenyl-substituted propargylplatinum(II) complex, trans-Pt(CH2C≡CPh)(Cl)(PPh3)2 (1) to allenyl complex, trans-Pt(CPh=C=CH2)(Cl)(PPh3)2 (2) was found to be catalyzed by zerovalent complex Pd(PPh3)4. The reaction was proposed to proceed through the transfer of the propargyl/allenyl ligand both from Pt(II) to Pd(0) and Pd(II) to Pt(0). The former transfer, which seemingly has a thermodynamic disadvantage, has unambiguously been confirmed to take place; treatment of 1 with Pd(PPh3)4 or a mixture of Pd2(dba)3 and PPh3 resulted in the formation of Pd(I) complex, Pd2(μ-PhCCCH2)(μ-Cl)(PPh3)2 which lies in equilibrium with a mixture of propargyl/allenylpalladium(II) and Pd(0) complexes.
- Ogoshi, Sensuke,Nishida, Takuma,Fukunishi, Yoshiaki,Tsutsumi, Ken,Kurosawa, Hideo
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p. 190 - 193
(2007/10/03)
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- Transition metal complexes incorporating the BF2 ligand formed by oxidative addition of the B-B bond in B2F4
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The reactions between B2F4 and the platinum and iridium complexes [Pt(PPh3)2(η-C2H4)], [Pt(dppb)(r)-C2H4)] [dppb = l,4-bis(diphenylphosphino)butane] and trans-[IrCl(CO)(PPh3)2] afforded the difluoroboryl complexes cis-[Pt(BF2)2(PPh3)2], cis-[Pt(BF2)2(dppb)] and fac-[Ir(BF2)3(CO)(PPh3)2] respectively all of which have been characterised by X-ray crystallography. The isoelectronic platinum dppb nitrito complex cw-[Pt(NO2)2(dppb)] has also been prepared and structurally characterised. The Royal Society of Chemistry 2000.
- Lu, Norman,Norman, Nicholas C.,Guy Orpen,Quayle, Michael J.,Timms, Peter L.,Whittell, George R.
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p. 4032 - 4037
(2007/10/03)
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- Reactions of organotin(IV) compounds with platinum complexes. Part II. Oxidative addition of SnRxCl4-x to [Pt(COD)2] and subsequent reactions with tertiary phosphines
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Organotin(IV) compounds SnRxCl4-x (R=Me, Ph; x=4-0) add oxidatively to [Pt(COD)2] (COD=cycloocta-1,5-diene) to yield platinum(II) complexes in which Pt has inserted into the Sn-Cl or Sn-R bonds, displacing one COD entity. The new com
- Al-Allaf, Talal A. K.
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- C-centred chiral metal alkyls,
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The chloro(alkyl)metallocenes [MR*(Cl)(η-C5H5)2] [R* = -CH(SiMe3)C6H4Me-o; M = Zr 1 or Hf 2] have been prepared from [MCl2(η-C5H5)2] and LiR*(tmen) (tmen = N,N,N′,N′-tetramethylethane-1,2-diamine); further alkylation occurred only for M = Zr, affording rac-3a and meso-3b, [ZrR*2(η-C5H5)2]. In contrast, reaction of 2 equivalents of Li[CH(SiMe3)2](tmen) with [ZrCl2(η-C5H5)2] yielded an alkyl elimination product possessing μ-η1:η5-C5H42- ligands. Compound 1 was reversibly reduced (E1/2red = -1.72 V vs. saturated calomel electrode, SCE) whereas 2, 3a or 3b were irreversibly reduced (Ered = -2.12, -2.08, -2.00 V respectively vs. SCE). Thermolysis of 3b in toluene gave 3a (80°C) or 'Zr(C10H8)' (120°C). Photolysis of 3a or 3b at 20°C in tetrahydrofuran (thf) yielded a 1:1 mixture of 3a and 3b; a d1 intermediate has been unambiguously identified as [ZrR*(η-C5H5)2]. Reduction of 1 (Na-Hg), or 3a and 3b (Na[C10H8]), in thf also gave [ZrR*(η-C5H5)2] but this slowly transformed into [ZrR*(η-C5H5)2(thf)], and 1 with Na[C10H8] and PPh3 gave [ZrR*(η-C5H5)2(PPh3)]. Reduction of 1, 3a or 3b, or photolysis of 3a or 3b, in the presence of PMe3 gave [ZrR*(η-C5H5)2(PMe3)]. Crystal structure determinations showed a slightly more crowded metal environment in 2 than in 1, consistent with the view that dialkylation in 2 is limited on steric grounds; M-σ-C 2.359(4) (1), 2.322(8) (2), metal-centroid 2.22 (1), 2.21 (2), M-Cl 2.444(1) (1), 2.418(3) (2) A. The structure of 3a confirms the rac assignment, M-σ-C 2.374 A, metal-centroid 2.23, 2.24 A.
- Lappert, Michael F.,Raston, Colin L.,Skelton, Brian W.,White, Allan H.
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p. 2895 - 2902
(2007/10/03)
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- Coordination chemistry of P-rich phosphanes and silylphosphanes. XIV. The phosphinophosphinidene tBu2P-P as a ligand in the Pt complexes [η2-{tBu2P-P}Pt(PPh3) 2] and [η2
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[η2-{tBu2P-P}Pt(PPh3) 2 1 and [η2-{tBu2P-P}Pt(PEtPh2)2] 2 are the first complex compounds of tBu2P-P 5. They are formed in the reactio
- Krautscheid,Matern,Kovacs,Fritz,Pikies
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p. 1917 - 1924
(2008/10/09)
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- Unexpected substitution reactions of bis(phosphine)platinum ethene complexes
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Reaction of [Pt(C2H4)(PR3)2] (R = Ph or C6H4Me-4) with moderately bulky phosphines at low temperatures did not give the expected tris- or tetrakis-phosphine complexes. Instead, mixed-phosph
- Chaloner, Penny A.,Broadwood-Strong, Gillian T. L.
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p. 1039 - 1043
(2007/10/03)
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- Syntheses, spectroscopic characteristics and thermolytic rearrangements of bis-[(trimethylgermyl) methyl]platinum(II) and bis-[(trimethylstannyl) methyl]platinum(II) complexes
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The preparations and spectroscopic characteristics are reported of a series of (trimethylgermyl)methyl- and (trimethylstannyl)methyl- platinum(II) complexes with diene and P-donor ancillary ligands, cis-Pt(CH2GeMe3)2L2 (L = PPh3 or PPh2Me; L2 = dppe or cod) and cis-Pt(CH2SnMe3)2L2 (L = PPh3; L2 = cod). Thermolysis of toluene solutions of cis-Pt(CH2GeMe3)2(PPh3)2 leads to cis-Pt(Me)(CH2GeMe2CH2GeMe3)(PPh3)2 via β-alkyl migration, after (non-rate-limiting) phosphine dissociation. Estimated activation parameters (ΔH298 K? = 126 ± 3 kJ mol-1, ΔS? = + 17 ± 7 J mol-1 K-1 and hence ΔG298 K? = 121 ± 5 kJ mol-1) suggest that this system is more migration labile than its silicon analogue, primarily as a result of a lower activation enthalpy. While cis-Pt(CH2GeMe3)2(PPh2Me)2 reacts similarly but less readily, Pt(CH2GeMe3)2(dppe)2 is inert at operable temperatures. Thermolysis of Pt(CH2GeMe3)2(cod) generates 1,1,3,3,-tetramethyldi-1,3-germacyclobutane as the major organogermanium product, while from cis-Pt(CH2SnMe3)2(PPh3)2, 1,1,3,3-tetramethyldi-1,3-stannacyclobutane predominates. Mechanistic implications are discussed.
- Christou, Victor,Young, G. Brent
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p. 157 - 165
(2007/10/03)
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- Platinum-mediated P=C bond cleavage in a phosphaketene: Formation and structure of the first mononuclear diphosphaureylene complex
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Reactions of Mes*P=C=O (1; Mes* = 2,4,6-(t-Bu)3C6H2) with (PPh3)2Pt(C2H4) (2) and (PCy3)2Pt (3; Cy = cyclo-C6H11) give the diphosphaur
- David, Marie-Anne,Glueck, David S.,Yap, Glenn P. A.,Rheingold, Arnold L.
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p. 4040 - 4042
(2008/10/09)
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- Regioselective carbon - Fluorine bond cleavage reactions from the interaction of transition-metal fluorocarbon complexes with nucleophiles
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The use of fluoro substituents has been tested as a means to stabilize the amide bond to divalent platinum. Products have been obtained which show that complexed fluoroalkyls and fluoroaryls have a high reactivity to nucleophiles. The complex trans-PtCF3Cl(PPh3)2 reacts with LiN(CH3)2 to give products derived from Pt(PPh3)2. The complex trans-[PtCH3(THF)-(PPh2C6F5) 2]ClO4, prepared from trans-PtCH3Cl(PPh2C6F5)2 and AgClO4 in THF solvent, reacts with hydroxide ion to give the cyclometalated complex trans-PtCH3(2-OC6F4PPh2)(PPh 2C6F5). The crystal structure of trans-PtCH3(2-OC6F4PPh2)(PPh 2C6F5) has a monoclinic P21/c cell with a = 12.437 (2) ?, b = 25.749 (8) ?, c = 10.788 (2) ?, β = 102.35 (1)°, Z = 4. Reaction of this complex with HCl results in ring opening to give trans-PtCH3Cl(2-HOC6F4PPh2)(PPh 2C6F5). Reacting trans-[PtCH3-(THF)(PPh2C6F5) 2]ClO4 with methoxide ion gives trans-PtCH3(OCH3)(PPh2C6F 3(OCH3-2,6)2)2, where all the fluorines in the 2-positions of the fluorophenyl rings have been replaced by methoxide. Treating this complex with water gives trans-PtCH3(2-OC6F3(OCH3-6)PPh 2)(PPh2C6F3(OCH 3-2,6)2). Heating a mixture of triphenylphosphine, bromopentafluorobenzene and nickel bromide at 200°C, followed by hydrolysis of the melt, gives the phosphonium salt [Ph3(C6F4H-4)P]Br. The use of D2O in the hydrolysis yields [Ph3(C6F4D-4)]Br. Hydroxide ion reacts with the phosphonium salt to give P-C cleavage. 1,2,4,5-Tetrafluorobenzene is formed from [Ph3(C6F4H-4)]Br and OH-, 1,2,4,5-tetrafluorodideuteriobenzene is formed from [Ph3(C6F4D-4)]Br and OD-, and 1,2,4,5-tetrafluoro-3-deuteriobenzene is formed from either [Ph3(C6F4H-4)]Br and OD- or [Ph3(C6F4D-4)]Brand OH-.
- Park, Soonheum,Pontier-Johnson, Marie,Roundhill, D. Max
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p. 2689 - 2697
(2008/10/08)
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- Formation of cationic MPt heterobimetallic μ-phosphido μ-hydrido complexes
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The cationic secondary phosphine complexes [CpM(CO)(L)(PR2H)]+X- (M = Ru, PR2H = PPh2H, PPhH2, L = CO; M = Fe, PR2H = PPh2H, L = CO, MeC≡CMe, C2H4; M = Mn PR2H = PCy2H, PPr2H, L = NO; X- = BF4-, PF6-) and [(η7-C7H7)(CO)2Mo(PCy2H]PF6, prepared by following literature procedures for the synthesis of their PPh3 analogues, react with Pt(C2H4)(PPh3)2 to give [Cp(L)M(μ-PR2)(μ-H)Pt(PPh3)2]X and [(η7-C7H7)(CO)Mo(μ-PCy2) (μ-H)Pt(PPh3)2]X as the final products. The reactions proceed by one or both, of two possible reaction pathways. One pathway involves the initial oxidative addition of a P-H bond to the Pt(0) complex to give [Cp(CO)LM(μ-PR2)PtH(PPh3)2]X followed by PPh3 loss from Pt and CO transfer from M to Pt (via a bridging CO). The rate of this CO-transfer step is sterically driven, in a manner similar to that observed for ortho-metalation reactions. The more acidic (P-H) secondary phosphine complexes react with Pt(0) complexes by a route that involves deprotonation of the coordinated secondary phosphine to give a phosphidometal complex, which then substitutes a ligand from Pt(0) followed by CO transfer to Pt. Several complexes of this type (PR3 = PCy3) were prepared and studied from the reaction of [CpM(CO)(L)(PR2H)]+ with Pt(C2H4)2(PCy3).
- Powell,Fuchs,Gregg,Phillips,Stainer
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p. 387 - 393
(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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- Hydrido-organometallic Complexes of Platinum(II). X-Ray Crystal Structure of trans-
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A series of compounds trans- , cis-, and cis- (dppe=Ph2PCH2CH2PPh2) have been obtained by decarboxylation of formate complexes, or by the reaction of the halogeno complexes with NaBH4.The compounds have been characterized by i.r. and n.m.r. ((1)H, (31)P, and (195)Pt) spectroscopy.The molecular structure of trans- has been determined by a single-crystal X-ray structural analysis.The crystals are orthorhombic, space group Pcab, with a=25.304(5), b=23.963(5), c=11.530(3) Angstroem, and Z=8.Dimethyl acetylenedicarboxylate inserts into the Pt-H bond of trans- (R=C6H4Cl-p, C6H4Me-p, or C6H4Me-o) to give the corresponding ?-vinyl complexes, but other alkynes and olefins do not react.The thermal stability in solution has also been studied; decomposition takes place via reductive elimination to give RH.The results obtained are explained in terms of the electronegativity and the size of the ligands and the configuration of the complexes.
- Crespo, Margarita,Sales, Joaquim,Solans, Xavier,Altaba, Manuel Font
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p. 1617 - 1622
(2007/10/02)
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- A convenient and novel route to bis(η-alkyne)platinum(0) and other platinum(0) complexes from Speier's hydrosilylation catalyst H2[PtCl6]·xH2O. X-ray structure of [Pt{(η-CH2=CHSiMe2)2O}(P-t-Bu3)]
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Evidence that the hydrosilylation catalyst, obtained by refluxing H2[PtCl6]·xH2O in (Me2ViSi)2O (solution A), is a Pt(0) species comprises (i) the isolation and X-ray characterization of [Rt{(η-CH2CHMe2Si)2O}(P-t-Bu3)], after addition of P-t-Bu3 to A, (ii) the convenient high-yield synthesis of various other Pt(0) complexes from A, and (iii) CV, GC/MS, and 195Pt NMR data.
- Chandra, Grish,Lo, Peter Y.,Hitchcock, Peter B.,Lappert, Michael F.
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p. 191 - 192
(2008/10/08)
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- Electrochemical generation and reactivity of bis(triphenylphosphine)platinum(0): An electrosynthesis of platinum-acetylene complexes
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Controlled potential bulk reductive electrolysis of cis-[PtCl2(PPh3)2] results in the generation of [Pt(PPh3)2] in solution. This 2-coordinate, 14-electron compound is efficiently trapped by acetylene
- Davies, Julian A.,Eagle, Cassandra T.,Otis, Deborah E.,Venkataraman, Uma
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p. 1264 - 1266
(2008/10/08)
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- MIXED LIGAND COMPLEXES OF ZEROVALENT PLATINUM, PALLADIUM AND NICKEL CONTAINING A CHELATING OLEFINIC TERTIARY PHOSPHINE
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The potentially chelating ligand (2-vinylphenyl)diphenylphosphine, o-CH2=CHC6H4PPh2(SP) reacts either with M(PPh3)2(C2H4) (M = Pt, Pd, Ni), or with M(1,5-COD)2 (M = Pt, Ni) and triphenylphosphine in a 1/2 mol ratio, to give mixed ligand complexes M(PPh3)2(SP).The platinum and palladium compounds can be isolated, whereas the nickel compound has been identified in solution by 1H and 31P NMR spectroscopy.All the complexes disproportionate readily, the palladium complex immediately on dissolution giving Pd(PPh3)(SP)2 and Pd(PPh3)3, the platinum and nickel complexes more slowly in solution to M(SP)2, M(PPh3)3 and PPh3.The platinum and nickel complexes contain bidentate SP and are probably tetrahedral, whereas Pd(PPh3)2(SP) in the solid state has a free vinyl group.In contrast to Ni(PPh3)2(SP), Pt(PPh3)2(SP) undergoes an intramolecular process in solution, probably one-ended dissociation of the vinyl group, which equivalences the triphenylphosphine ligands; this process can be frozen at -117 deg C.Both Ni(PPh3)2(SP) and Pt(PPh3)2(SP) undergo intermolecular ligand exchange, above -50 deg C in the case of platinum, above -30 deg C in the case of nickel; the triphenylphosphine ligands of Ni(PPh3)2(SP) exchange at different rates.The results can be correlated with the trend in equilibrium constants for the reaction M(PPh3)3+C2H4M(PPh3)2(C2H4)+PPh3(M = Ni > Pt > Pd).
- Bennett, Martin A.,Chiraratvatana, Chindarat
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p. 255 - 268
(2007/10/02)
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- Electrophilic Behaviour of Dicarbonylbis(pentamethylcyclopentadienyl)-dirhodium towards Diazoalkanes and Low-valent Platinum Compounds: X-Ray Crystal Structure of
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The diazoalkanes R1R2CN2 react with the dirhodium compound to give the complexes 1R2)(CO)2(η-C5Me5)2> (R1=R2=H or CF3; R1=H, R2=CO2Et; R1=H, R2=CH=CH2), the i.r and n.m.r. data for which are reported and discussed.The dirhodiumplatinum compounds (cod=cyclo-octa-1,5-diene), , and have been isolated from reactions between low-valent platinum species and or .Spectroscopic properties are reported which are in accord with molecular structures in which PtL2 fragments are 'complexed' with a molecule giving rise to a PtRh2 triangle semi-triply bridged by two CO ligands.This has been confirmed by an X-ray diffraction study on 3-CO)2(CO)(PPh3)(η-C5Me5)2>, crystals of which are triclinic, space group P1, in a unit cell with a=11.185(3), b=13.278(7), c=15.443(9) Angstroem, α=102.98(5), β=92.18(4), γ=105.88(4) deg, and Z=2.The structure was solved to R 0.056 (R' 0.058) from 4 285 observable independent reflections =3.0?(I)> collected at 220 K in the range 2Θa triangle of metal atoms .The platinum atom is in a planar environment with respect to the two rhodium atoms and the CO and the PPh3 ligands to which it is terminally bound.The longer Pt-Rh bond is essentially trans to CO.On either face of the metal triangle two other CO ligands bridge the Rh-Rh bond and lean towards the platinum in a semi-triply bridging manner .Each rhodium is η5-co-ordinated to a C5Me5 group, as expected.The reaction between and affords the thermally unstable and air sensitive complex , while the salt has been prepared from and .The i.r and n.m.r. data for these species are discussed.
- Green, Michael,Mills, Rona M.,Pain, Geoffrey N.,Stone, F. Gordon A.,Woodward, Peter
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p. 1309 - 1320
(2007/10/02)
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- DEPROTONATION REACTIONS BY TRANSITION-METAL PEROXO-COMPLEXES. SYNTHESIS OF AROYLHYDRAZIDO- AND AROYLHYDROXYLAMIDO-COMPLEXES OF PALLADIUM AND PLATINUM AND THE CRYSTAL AND MOLECULAR STRUCTURES OF AND
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By treating (M = Pd or Pt) with C6H5C(O)NHOH, C6H5(NH)NHOH, and p-RC6H4C(O)NHNH2 in ethanol, the complexes , , and (R = H, CH3, or NO2) respectively have been obtained.The reactions of with RNHNH2 (R = H or C6H5) lead only to the zerovalent complex, , while by treating with C6H5NHOH the known complex is obtained.Reactions of the aroylhydrazidoplatinum complexes with molecular oxygen and mineral acids are also reported.The structure of the two title complexes has been determined by X-ray diffraction.The compound is orthorhombic and crystallizes in space group Pna21 with a = 17.365(6), b = 11.218(7), and c = 18.431(8) Angstroem, whereas the disordered is monoclinic and crystallizes in space group P2n1/m with a = 15.829(6), b = 12.269(5), c = 11.833(5) Angstroem, and β = 93.51(3) deg.Both structures have been solved by Patterson and Fourier methods, and refined to R 0.031 and 0.062 for 2057 and 2119 independent reflections, respectively.Both compounds, in the solid state, are essentially square-planar complexes of PtII.The differences between the two structures, which display different packing efficiency, are mainly due to the conformations of the phosphine groups, which are imposed by the chelating ligands.
- Bellon, Pier Luigi,Cenini, Sergio,Demartin, Francesco,Manaserro, Mario,Pizzotti, Maddalena,Porta, Francesca
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p. 2060 - 2067
(2007/10/02)
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