53199-31-8Relevant articles and documents
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.
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.
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.
