- Selective synthesis and formation mechanisms of trans- and cis-benzoyl(carbamoyl)platinum(II) complexes coordinated with tertiary phosphine ligands
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trans-Pt(COPh)Cl(PPh3)2 (1) reacts with secondary amines under CO pressure (10 atm) at room temperature to give cis-Pt(COPh)(CONR2)(PPh3)2 complexes (NR2 = NMe2 (5a), N(CH2)4CH2 (5b), N(CH2)3CH2 (5c), NEt2 (5d)) exclusively, while the same amines react with trans-[Pt(COPh)(CO)(PPh3)2]BF4 (7) under a nitrogen atmosphere to afford trans-Pt(COPh) (CONR2) (PPh3)2 complexes (NR2 = NMe2 = NMe2 (6a), N(CH2)4CH2 (6b), N(CH2)3CH2 (6c), NEt2 (6d)). The isomerization of the trans-benzoylcarbamoyl complexes (6a-d) to their cis isomers (5a-d) in a neat solvent is a slow process, but the isomerization is significantly accelerated by addition of amine and CO. On the other hand, benzoylplatinum complexes coordinated with compact and basic PMe3 ligands, trans-Pt(COPh)Cl(PMe3)2 (2) and trans-[Pt(COPh)(acetone)(PMe3)2]BF4 (4), give trans-Pt(COPh)(CONR2)(PMe3)2 (9) exclusively on treatment with CO and the secondary amines. Complex 9 is inert to isomerization to its cis isomer. Formation pathways of irons- and cis-benzoyl(carbamoyl)platinum complexes and their trans-cis isomerization process are examined in detail, and a new type of isomerization pathway involving participation of added CO and amine is proposed.
- Huang, Li,Ozawa, Fumiyuki,Yamamoto, Akio
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- σ-bond metathesis between M-X and RC(O)X′ (M = Pt, Pd; X, X′ = Cl, Br, I): Facile determination of the relative Δ G values of the oxidative additions of RC(O)X to an M(0) complex, evidence by density functional theory calculations, and synthetic applications
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The novel utility of the ligand exchange reaction between M-X and RC(O)X′ (X, X′ = halogen; R = aryl, alkyl) is described. The relative ΔGs (ΔΔGs) of the oxidative additions of acid halides RC(O)X to M(PPh3)2Ln (M = Pt, Pd) were determined using the halogen-exchange reactions between X of trans-M(X)[C(O)R](PPh3)2 and X′ of RC(O)X′. Experimental thermodynamics data are reasonably consistent with those obtained by density functional theory (DFT) calculations. Activation parameters obtained by experiments as well as a systematic DFT study supported the fact that reactions occurred through slightly distorted quadrangular pentacoordinated σ-bond metatheses, in which the Cl atom underwent a more indirect course than the Br atom. Moreover, exchange reactions were employed as the accessible prototype for the conversion of halogen ligands of nickel triad complexes into heavier halogen ligands.
- Kuniyasu, Hitoshi,Sanagawa, Atsushi,Nakane, Daisuke,Iwasaki, Takanori,Kambe, Nobuaki,Bobuatong, Karan,Lu, Yunpeng,Ehara, Masahiro
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supporting information
p. 2026 - 2032
(2013/05/09)
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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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- Synthesis, Characterization, and Reactivity of α-Ketoacyl Complexes of Platinum(II) and Palladium(II). Crystal Structures of trans-Pt(PPh3)2(Cl)(COCOPh) and cis-Pt(PPh3)2(COPh)(COOMe)
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The α-ketoacyl chloro complexes, trans-M(PPh3)2(Cl)(COCOR) (M = Pt; R = Ph, 1a; R = p-FC6H4, 1b; R = p-ClC6H4, 1c; R = p-MeC6H4, 1d; R = Me, 1e.M = Pd: R = Ph, 2), were synthesized by the oxidative addition of the appropriate α-ketoacyl chloride with either Pt(PPh3)4 or Pd(PPh3)4.The crystal structure of 1a showed a square-planar geometry around the Pt with the carbonyl groups virtually coplanar and in an s-trans configuration.The above compounds were found to decompose thermally to the corresponding benzoyl compounds, trans-M(PPh3)2(Cl)(COR).A detailed kinetic study of the decarbonylation of 1a and 2 indicated the presence of two competing pathways, one of which involved the initial dissociation of a PPh3 ligand.The kinetic and thermodynamic parameters for the various steps in the mechanism were determined.For the decarbonylation of compounds 1a-d, a correlation was observed between the rate constant for the phosphine-independent pathway and ?para.The cationic α-ketoacyl complexes, trans-Pt(PPh3)2(L)(COCOR)+BF4- (R = Ph; L = CH3CN, 4a; L = CO, 4b; L = PPh3, 4c.R = Me; L = CH3CN, 4d), were prepared by Cl- abstraction from the corresponding neutral compounds in the presence of an appropriate ligand.In the absence of any added ligand, the Cl- abstraction from 1a resulted in rapid deinsertion of CO to form cis-Pt(PPh3)2(CO)(COPh)+ (5a) initially, which then slowly converted to the corresponding trans compound, 5b.The decarbonylation of 1a to the corresponding chloro benzoyl compound was catalyzed by the addition of 5b.The addition of OMe- to 5a and 5b resulted in the formation of the acyl-alkoxycarbonyl complexes cis- and trans-Pt(PPh3)2(COPh)(COOMe), 6a and 6b, respectively.Similarly, trans-Pt(PPh3)2(COCOPh)(COOMe) (6d) was formed by the reaction of OMe- with 4b.The crystal structure of 6a revealed a square-planar geometry around the Pt with the CoPh and COOMe groups lying in planes perpendicular to the plane of the molecule.
- Sen, Ayusman,Chen, Jwu-Ting,Vetter, William M.,Whittle, Robert R.
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p. 148 - 156
(2007/10/02)
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- PLATINUM(II) TRICHLOROSTANNATE CHEMISTRY. ON THE IMPORTANCE OF THE Pt-Sn LINKAGE IN HYDROFORMYLATION CHEMISTRY AND A NOVEL PtC(OSnCl2)R-CARBENE
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The reaction of trans-PtCl(COR)(PPh3)2 (1) (R=a, C6H5; b, C6H4-p-NO2; c, C6H4-p-CH3; d, C6H4-p-OCH3; e, CH3; f, Et; g, Prn; h, Hexn; i, CH2CH2Ph; j, But) with SnCl2 and SnCl2 plus H2 are described.The reactions with SnCl2 alone afford a mixture of trans-Pt(SnCl3)(COR)(PPh3)2 (2), and trans-PtCl(PPh3)2 (3) with 3 having a tin-oxygen bond.For 1f, 1h and 1j, reactions with SnCl2 plus H2 give aldehydes and platinum(II) hydride complexes, whereas for 1b and 1d, no aldehydes are obtained.The significance of these results in relation to H2 activation in the hydroformylation reaction is discussed. 31 P, 119 Sn, 195 Pt and, in a few cases, 13 C NMR data are presented.
- Ruegg, H. J.,Pregosin, P. S.,Scrivanti, A.,Toniolo, L.,Botteghi, C.
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p. 233 - 242
(2007/10/02)
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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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- Reactivity of platinum diolefin complexes. 2. Reactions with bulky and chelating group 5B ligands and studies relating to carbonyl insertion
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Reactions of [PtXY(cod)] (X = Y = Cl, Me, Ph; X = Cl, Y = Ph, COPh) with bulky monodentate and chelating group 5B ligands have been examined by 31P{1H} NMR spectroscopy. The molecularity of the products is a function of steric bulk with monodentate ligands and a function of chelate bite with bidentate ligands. The geometry of the products is controlled largely by the trans influence of both neutral and anionic groups. Where the steric constraints involved in nucleophilic attack of the complexes by bulky ligands are dominant, olefin displacement can be prevented entirely. Reactions of [PtXYL2] (X = Y = Ph, Cl; X = Ph, Y = Cl; L = monodentate ligand, L2 = bidentate ligand) with carbon monoxide have been studied by 31P{1H} and 13C{1H} NMR and infrared spectroscopies. The mechanism of carbonyl insertion at platinum(II) is discussed in terms of the chelate effect and the trans influence of the anionic ligands.
- Anderson,Clark,Davies
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p. 3607 - 3611
(2008/10/08)
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- Carbonylation of . New Intermediates in the CO Insertion Sequence
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Phosphorus-31 n.m.r. studies of the reaction of trans- with carbon monoxide have led to the identification of several new intermediates and reaction pathways involved in the CO insertion process to produce trans-.Carbonyl addition forms a metastable five-co-ordinate compound in non-polar solvents, which eliminates a halide to form ionic species trans-X in polar solvents.Loss of PR3 from five-co-ordinate intermediates produces two isomers of which convert to the remaining isomer with Ph trans to PR3 before migration of Ph proceeds to form a benzoyl complex.A direct carbonyl insertion route from a five-co-ordinate intermediate also operates, independently of the phosphine elimination pathways, and this becomes the predominant pathways with more nucleophilic PR3 ligands.The use of elemental sulphur to remove PR3 from the reaction mixtures was instrumental in identifying some intermediates, and this method has potential synthetic value in replacing PR3 by weaker ligands at platinum.
- Anderson, Gordon K.,Cross, Ronald J.
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p. 1434 - 1438
(2007/10/02)
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