75983-00-5Relevant academic research and scientific papers
Facile regio- and stereoselective hydrometalation of alkynes with a combination of carboxylic acids and group 10 transition metal complexes: Selective hydrogenation of alkynes with formic acid
Shen, Ruwei,Chen, Tieqiao,Zhao, Yalei,Qiu, Renhua,Zhou, Yongbo,Yin, Shuangfeng,Wang, Xiangbo,Goto, Midori,Han, Li-Biao
, p. 17037 - 17044 (2011/12/04)
A facile, highly stereo- and regioselective hydrometalation of alkynes generating alkenylmetal complex is disclosed for the first time from a reaction of alkyne, carboxylic acid, and a zerovalent group 10 transition metal complex M(PEt3)4 (M = Ni, Pd, Pt). A mechanistic study showed that the hydrometalation does not proceed via the reaction of alkyne with a hydridometal generated by the protonation of a carboxylic acid with Pt(PEt 3)4, but proceeds via a reaction of an alkyne coordinate metal complex with the acid. This finding clarifies the long proposed reaction mechanism that operates via the generation of an alkenylpalladium intermediate and subsequent transformation of this complex in a variety of reactions catalyzed by a combination of Bronsted acid and Pd(0) complex. This finding also leads to the disclosure of an unprecedented reduction of alkynes with formic acid that can selectively produce cis-, trans-alkenes and alkanes by slightly tuning the conditions.
Syntheses, structures, and reductive elimination studies of six-membered diaryl platinacycle complexes
Robinson Jr., Robert,Sharp, Paul R.
, p. 1388 - 1395 (2010/05/15)
The six-membered platinacycles PtL2(C6H 4XC6H4) (X = CH2, O, NMe; L = PEt3, L2 = 1,3bis(diphenylphosphino)propane (dppp), 4,4'-bis-rerr-butyl-2,2'-bipyridine (tBu 2bpy)), have been prepared from. Cw-PtL2Cl2 and the appropriate dilithio reagents. Reductive elimination studies on the platinacycles with L = PEt3 show that the bridging group (X) dramatically influences the reductive elimination rate. Thermodynamic activation parameters were determined for the platinacycles and showed a ΔH* trend X = NMe O 2 with an essentially zero value for ΔS*. Rate constants at 95 °C show over a million-fold increase on going from X = CH2 to X = NMe. DFT calculations support direct elimination without phosphine ligand loss and indicate a progressively earlier transition state in the series X = CH2,O, NMe. The earlier transition state and the accelerated rate are associated with the beginning of aromatization in the eliminating organic unit. Computed thermodynamic activation parameters are in good agreement with the experimental results.
Highly selective markovnikov addition of hypervalent H-spirophosphoranes to alkynes mediated by palladium acetate: Generality and mechanism
Han, Li-Biao,Ono, Yutaka,Xu, Qing,Shimada, Shigeru
, p. 1086 - 1099 (2010/11/05)
Palladium acetate efficiently catalyzes the addition of an H-spirophosphorane (pinacolato)2PH to alkynes to give Markovnikov addition products highlyselectively. The addition products can be easily converted to the corresponding alkenylphosphonates and phosphonicacids viasimple hydrolysis or thermal decomposition. This new reaction isa general method for the introduction of phosphorus functionality to the internal carbons of terminal alkynes, resolving the problem of the regioselectivity associated with hydrophosphorylation reactions so far reported. Mechanistic studies confirmed that (a) palladium acetate was reduced to metallic palladium by H-spirophosphorane, (b) the P-H bond of H-spirophosphorane could be activated by zero-valent platinum complexes to give the corresponding hydridoplatinum complexes, and (c) an alkenylpalladium species was identified from the reaction of palladium acetate with H- spirophosphorane and diphenylacetylene. These results support a reaction mechanism that palladium acetate was first reduced by H-spirophosphorane to give zero-valent palladium. This zero-valent palladium might insert into the P-H bond of the H-spirophosphorane to give a hydridopalladium species which then added to alkyne via the addition of H-Pd bond to form an alkenylpalladium species with the hydrogen atom added to the terminal carbon of alkynes. Reductive elimination of the alkenylpalladium affords the addition product.
Autocatalytic alkyne cycloadditions: Evidence for colloidal Pt catalysis
Begum, Rowshan Ara,Chanda, Nripen,Ramakrishna,Sharp, Paul R.
, p. 13494 - 13495 (2007/10/03)
Treatment of the four-membered platinacycle L2Pt(1,8-naphthalendiyl) (1) or the five-membered platinacycle L2Pt(1,12-triphenylendiyl) with excess PhCCPh at 120-150 °C gives the coupling products 1,2-diphenylacenaphthalene or 4,5-diphenylbenzo[e]pyrene and the alkyne complex L2Pt(η2-PhCCPh). Both reactions show an accelerating rate, which has been traced to catalysis of the reaction by colloidal platinum formed by the reaction of O2 with L2Pt(η2-PhCCPh). Copyright
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
Davies, Julian A.,Eagle, Cassandra T.,Otis, Deborah E.,Venkataraman, Uma
, p. 1080 - 1088 (2008/10/08)
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).
Syntheses, Reactions, and Molecular Structures of trans-Hydrido(phenylamido)bis(triethylphosphine)platinum(II) and trans-Hydridophenoxobis(triethylphosphine)platinum(II)
Cowan, Robert L.,Trogler, William C.
, p. 4750 - 4761 (2007/10/02)
The reaction between trans-PtH(NO3)(PEt3)2 and NaNHPh in C6H6 yields the novel hydridoamido complex trans-PtH(NHPh)(PEt3)2 (I).This compound is stable in solution; however, crystals of I decompose within hours at room temperature.At -100 deg C a crystal of I belongs to the monoclinic space group P21/n with a = 11.445(2) Angstroem, b = 13.010(2) Angstroem, c = 14.888(2) Angstroem, β = 104.63(1) deg, V = 2144.9(6) Angstroem3, and Z = 4.Complex I adopts a trans structure, with Pt-N = 2.125(5) Angstroem, indicative of a single bond weakened by the trans-hydride ligand.The Pt-N-Ph angle of 125.5(4) deg and the observation of the H on N in a position expected for trigonal-planar coordination suggest sp2 hybridization about nitrogen.SCF-DV-Xα calculations of the model complex PtH(NH2)(PH3)2 confirm the expected repulsive nature of the interaction between the nitrogen lone-pair orbital and filled d? orbitals on the metal.This interaction is minimized when the nitrogen lone pair lies in the coordination plane of Pt.The reaction between trans-PtH(NO3)(PEt3)2 and excess NaOPh produces trans-PtH(OPh)(PEt3)2 (II).Crystals of II belong to the triclinic space group PI, and at -50 deg C a = 9.477(3) Angstroem, b = 10.617(3) Angstroem, c = 11.641(3) Angstroem, α = 101.61(2), β = 98.28(2) deg, γ = 104.13(2), V = 1089.5(5) Angstroem3, and Z = 2.This complex is isostructural to I with Pt-O = 2.098(9) Angstroem and Pt-O-Ph = 123.6(7) deg.Complex I undergoes rapid insertion of electrophilic substrates such as CO2.COS, and PhNCO into the Pt-NHPh bond in preference to the metal hydride bond.These reactions in C6H6 solvent do not appear to involve free NHPh(1-) as evidenced by the reaction between PtH((15)NHPh)(PEt3)2, which exclusively yields PtH(PEt3)2 as the initial product.Crossover between PtH(NHPh)(PEt3)2 and PtD((15)NHPh)(PEt3)2 to form PtH((15)NHPh)(PEt3)2 and PtD(NHPh)(PEt3)2 occurs slowly (t1/2 ca. 48 h) at room temperature.Electrophiles such aas CH3I and H2O directly attack bound aniline in PtD(NHPh)(PEt3)2 to produce trans-PtDI(PEt3)2 and trans-PtD(OH)(PEt3)2, along with NH(CH3)Ph and NH2Ph, respectively.The electrophilic olefin acrylonitrile inserts into the Pt-N bond to form trans-PtH(PEt3)2 (III).Crystals of III belong to the monoclinic space group P21/c and at 22 deg C a = 14.260(6) Angstroem, b = 14.021(6) Angstroem, c = 13.240(6) Angstroem, β = 107.96(3) deg, V = 2519(3) Angstroem3, and Z = 4.The structure shows a 3-anilinopropionitrile ligand trans to hydride ?-bound to platinum (Pt-C = 2.198(13) Angstroem) by the 2-carbon atom.Complex III undergoes C-H reductive elimination on heating to 70 deg C to produce 3-anilinopropionitrile.Methyl acrylate appears to undergo a similar insertion reaction; however, the organic product is unstable toward elimination in the presence of "Pt(PEt3)2"...
