53199-31-8Relevant academic research and scientific papers
A dinuclear palladium(I) ethynyl complex: Synthesis, structure, and dynamics
Krause, Jochen,Goddard, Richard,Mynott, Richard,P?rschke, Klaus-Richard
, p. 1992 - 1999 (2001)
The reaction of Pd(η3-C3H5)2 with PiPr3 at -30°C affords yellow crystals of the PdII complex (iPr3P)Pd(η3-C3H5) (η1-C3H5) (1). At 20°C 1 transforms into the dinuclear PdI complex {(iPr3P)Pd}2 (μ-C3H5)2 (2) due to oxidative C-C coupling of two allyl groups with elimination of 1,5-hexadiene. Heating 1 or 2 in 1,6-heptadiene to 80°C produces the Pd0 complex (iPr3P)Pd(η2,η2- C7H12) (3) {(η3-C3H5)PdCl}2 reacts with iPr3P to give (iPr3P)Pd(η3-C3H5)Cl (4b), from which further derivatives (iPr3P)Pd(η3-C3H5)X (X = OSO2CF3 (4a), C≡CH (5a), CH3 (5b)) are obtained by replacement reactions. The mononuclear PdII-acetylide 5a and complex 3 combine to give the dinuclear PdI derivative {(iPr3P)Pd}2(μ-C3H5) (μ2-η2-C2H) (6). The Pd-Pd bond in 6 is unsymmetrically bridged by a π-allyl and a σ-π-ethynyl group, as determined by X-ray structure analysis. The structures of 1, 4a,b, and 6 are dynamic in solution, with 1 undergoing an exchange of the binding modes of the π- and σ-coordinated allyl groups and 4a,b displaying a π/σ-allyl group rearrangement, and in 6 the C≡CH substituent oscillates in its π-coordination from one PdI atom to the other.
A cluster model for the catalytic hydrogenation of CFCs and the synthesis and structural characterisation (when X = Br) of [Pd4(μ3-CF)(μ-X)3(PBut 3)4] (X = Cl, Br)
Vilar, Ramon,Lawrence, Simon E.,Mingos, D. Michael P.,Williams, David J.
, p. 285 - 286 (1997)
The syntheses, characterisation and crystal structure (when X = Br) of [Pd4(μ3-CF)(μ-X)3(PBut 3)4] (X = Cl, Br) are reported; the μ3-CF moiety is hydrogenated to CFH3 under mild conditions and serves as a model for the heterogeneous hydrogenation of CFCs to HCFCs.
NMR Studies of the Species Present in Cross-Coupling Catalysis Systems Involving Pd(η3-1-Ph-C3H4) (η5-C5H5).
Borjian, Sogol,Baird, Michael C.
, p. 3936 - 3940 (2014)
The compounds Pd(η3-1-Ph-C3H4) (η5-C5H5) (I), Pd2(dba) 3 (II), Pd(OAc)2 (III), and [Pd(η3-1-Ph- C3H4)Cl]2 (IV) are frequently utilized as catalyst precursors for a variety of cross-coupling processes, including Suzuki-Miyaura, Heck-Mizoroki, Sonogashira, and Buchwald-Hartwig reactions. In the preceding paper in this issue, we assess and compare catalyst systems based on I-IV activated with PBut3, XPhos, and/or Mor-Dalphos for the prototypical Buchwald-Hartwig amination reactions of 4-bromo- and 4-chloroanisole with morpholine, noting several apparent incongruities which seem to indicate mechanistic dissimilarities for various reactant/precatalyst combinations. In this paper we investigate by NMR spectroscopy the solution chemistry of I and IV with PBut3, XPhos, and Mor-Dalphos, noting similarities and differences in the respective abilities of these precursor-ligand combinations to generate palladium(0) catalyst systems. We find inter alia that steric requirements prevent Xphos and Mor-Dalphos from forming 2:1 palladium(0) complexes and, surprisingly, that 1:1 palladium(0) complexes of Xphos and Mor-Dalphos are unstable with respect to dissociation to free ligand and palladium metal. In other words, these two ligands and, by implication, other sterically demanding phosphine ligands do not form palladium(0) compounds.
Ligand effects on decarbonylation of palladium-acyl complexes
Wiessner, Tedd C.,Fosu, Samuel Asiedu,Parveen, Riffat,Rath, Nigam P.,Vlaisavljevich, Bess,Tolman, William B.
supporting information, p. 3992 - 3998 (2020/11/30)
The influences of perturbations of supporting phosphine ligands on the dehydrative decarbonylation of (Ln)PdII(Cl)-hydrocinnamoyl complexes (L = PtBu3, n = 1; L = PPh3, n = 2; L = dppe, n = 1) to yield styrene were studied through combined experiment and theory. Abstraction of chloride from the complexes by silver and zinc salts, as well as sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, enhanced the efficiency of styrene formation, according to the following trend in L: PtBu3 > dppe > PPh3. DFT calculations corroborated the experimental findings and provided insights into the ligand influences on reaction step barriers and transition state structures. Key findings include the following: a stable intermediate forms after chloride abstraction, from which β-hydride elimination is most affected by ligand choice, the low coordination number for the PtBu3 case lowers reaction barriers for all steps, and the trans disposition of two ligands for L = PPh3 contributes to the low efficiency for styrene production in that case.
Oxidative ring expansion of a low-coordinate palladacycle: Synthesis of a robust T-shaped alkylpalladium(II) complex
Sinclair, Matthew J.G.,Chaplin, Adrian B.
, (2020/10/13)
The synthesis of an unusual T-shaped alkylpalladium(II) complex featuring a cyclometalated tri-tert-butylphosphineoxide ligand by oxidation of the corresponding cyclometalated tri-tert-butylphosphine complex with PhIO is reported. We speculate that this reaction proceeds by formation of a transient palladium oxo intermediate and there are structural similarities with a late transition metal exemplar: Milstein's seminal pincer ligated Pt(IV) oxo (Nature 2008, 455, 1093–1096).
General C-H Arylation Strategy for the Synthesis of Tunable Visible Light-Emitting Benzo[a]imidazo[2,1,5-c,d]indolizine Fluorophores
Lévesque, éric,Bechara, William S.,Constantineau-Forget, Léa,Pelletier, Guillaume,Rachel, Natalie M.,Pelletier, Joelle N.,Charette, André B.
supporting information, p. 5046 - 5067 (2017/05/24)
Herein we report the discovery of the benzo[a]imidazo[2,1,5-c,d]indolizine motif displaying tunable emission covering most of the visible spectrum. The polycyclic core is obtained from readily available amides via a chemoselective process involving Tf2O-mediated amide cyclodehydration, followed by intramolecular C-H arylation. Additionally, these fluorescent heterocycles are easily functionalized using electrophilic reagents, enabling divergent access to varied substitution. The effects of said substitution on the compounds' photophysical properties were rationalized by density functional theory calculations. For some compounds, emission wavelengths are directly correlated to the substituent's Hammett constants. Easily introduced nonconjugated reactive functional groups allow the labeling of biomolecules without modification of emissive properties. This work provides a straightforward platform for the synthesis of new moderately bright fluorescent dyes remarkable for their chemical stability, predictability, and unusually high excitation-emission differential.
Understanding the Unusual Reduction Mechanism of Pd(II) to Pd(I): Uncovering Hidden Species and Implications in Catalytic Cross-Coupling Reactions
Johansson Seechurn, Carin C. C.,Sperger, Theresa,Scrase, Thomas G.,Schoenebeck, Franziska,Colacot, Thomas J.
supporting information, p. 5194 - 5200 (2017/05/04)
The reduction of Pd(II) intermediates to Pd(0) is a key elementary step in a vast number of Pd-catalyzed processes, ranging from cross-coupling, C-H activation, to Wacker chemistry. For one of the most powerful new generation phosphine ligands, PtBu3, oxidation state Pd(I), and not Pd(0), is generated upon reduction from Pd(II). The mechanism of the reduction of Pd(II) to Pd(I) has been investigated by means of experimental and computational studies for the formation of the highly active precatalyst {Pd(μ-Br)(PtBu3)}2. The formation of dinuclear Pd(I), as opposed to the Pd(0) complex, (tBu3P)2Pd was shown to depend on the stoichiometry of Pd to phosphine ligand, the order of addition of the reagents, and, most importantly, the nature of the palladium precursor and the choice of the phosphine ligand utilized. In addition, through experiments on gram scale in palladium, mechanistically important additional Pd- and phosphine-containing species were detected. An ionic Pd(II)Br3 dimer side product was isolated, characterized, and identified as the crucial driving force in the mechanism of formation of the Pd(I) bromide dimer. The potential impact of the presence of these side species for in situ formed Pd complexes in catalysis was investigated in Buchwald-Hartwig, α-arylation, and Suzuki-Miyaura reactions. The use of preformed and isolated Pd(I) bromide dimer as a precatalyst provided superior results, in terms of catalytic activity, in comparison to catalysts generated in situ.
Synthetic method used for preparing bis(tri-tert-butylphosphine) palladium (O)
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Paragraph 0014-0015, (2017/03/08)
The invention provides a synthetic method used for preparing bis(tri-tert-butylphosphine) palladium (O). The synthetic method is high in yield and low in cost. According to the synthetic method, tri-tert-butylphosphonium tetrafluoroborate is reacted with two bivalent palladium compounds, tris(dibenzylideneacetone)dipalladium-chloroform adduct and dibromo(1,5-cyclooctadiene) palladium so as to obtain bis(tri-tert-butylphosphine) palladium (O) in an alkaline environment. The synthetic method is used for solving problems of the prior art that raw materials are expensive, yield is low, and reaction conditions are strict; and yield of the synthetic method is higher than 50%. The synthetic method possesses excellent popularization potential, and a promising application prospect.
Acid Chloride Synthesis by the Palladium-Catalyzed Chlorocarbonylation of Aryl Bromides
Quesnel, Jeffrey S.,Kayser, Laure V.,Fabrikant, Alexander,Arndtsen, Bruce A.
supporting information, p. 9550 - 9555 (2015/06/30)
We report a palladium-catalyzed method to synthesize acid chlorides by the chlorocarbonylation of aryl bromides. Mechanistic studies suggest the combination of sterically encumbered PtBu3 and CO coordination to palladium can rapidly equilibrate the oxidative addition/reductive elimination of carbon-halogen bonds. This provides a useful method to assemble highly reactive acid chlorides from stable and available reagents, and can be coupled with subsequent nucleophilic reactions to generate new classes of carbonylated products. The Good, the Bad and the Bulky! By employing a sterically encumbered phosphine ligand, tri-tert-butyl phosphine, under palladium catalysis inert aryl bromides are chlorocarbonylated to create reactive acid chlorides by reversible carbon-halogen bond reductive elimination. This general platform allows for an expanded scope of the Heck carbonylation reaction to include previously incompatible nucleophiles.
Highly Efficient C-SeCF3 Coupling of Aryl Iodides Enabled by an Air-Stable Dinuclear PdI Catalyst
Aufiero, Marialuisa,Sperger, Theresa,Tsang, Althea S.-K.,Schoenebeck, Franziska
supporting information, p. 10322 - 10326 (2015/09/01)
Building on our recent disclosure of catalysis at dinuclear PdI sites, we herein report the application of this concept to the realization of the first catalytic method to convert aryl iodides into the corresponding ArSeCF3 compounds. Highly efficient C-SeCF3 coupling of a range of aryl iodides was achieved, enabled by an air-, moisture-, and thermally stable dinuclear PdI catalyst. The novel SeCF3-bridged dinuclear PdI complex 3 was isolated, studied for its catalytic competence and shown to be recoverable. Experimental and computational data are presented in support of dinuclear PdI catalysis.
