30643-33-5Relevant articles and documents
Orthogonal Nanoparticle Catalysis with Organogermanes
Fricke, Christoph,Sherborne, Grant J.,Funes-Ardoiz, Ignacio,Senol, Erdem,Guven, Sinem,Schoenebeck, Franziska
supporting information, p. 17788 - 17795 (2019/11/13)
Although nanoparticles are widely used as catalysts, little is known about their potential ability to trigger privileged transformations as compared to homogeneous molecular or bulk heterogeneous catalysts. We herein demonstrate (and rationalize) that nanoparticles display orthogonal reactivity to molecular catalysts in the cross-coupling of aryl halides with aryl germanes. While the aryl germanes are unreactive in LnPd0/LnPdII catalysis and allow selective functionalization of established coupling partners in their presence, they display superior reactivity under Pd nanoparticle conditions, outcompeting established coupling partners (such as ArBPin and ArBMIDA) and allowing air-tolerant, base-free, and orthogonal access to valuable and challenging biaryl motifs. As opposed to the notoriously unstable polyfluoroaryl- and 2-pyridylboronic acids, the corresponding germanes are highly stable and readily coupled. Our mechanistic and computational studies provide unambiguous support of nanoparticle catalysis and suggest that owing to the electron richness of aryl germanes, they preferentially react by electrophilic aromatic substitution, and in turn are preferentially activated by the more electrophilic nanoparticles.
Rate and mechanism of the oxidative addition of benzoic anhydride to palladium(O) complexes in DMF
Jutand, Anny,Negri, Serge,De Vries, Johannes G.
, p. 1711 - 1717 (2007/10/03)
The rate constant of the oxidative addition of the benzoic anhydride (PhCO)2O to [Pd0(PPh3)4] has been determined in DMF and compared to that of phenyl halides and phenyl triflate. The following reactivity order has been established: PhI >> (PhCO)2O > PhOTf > PhBr. The oxidative addition of (PhCO)2O proceeds by activation of one C-O bond. Two acyl-PdII complexes are formed: a neutral complex trans-[(PhCO)Pd(OCOPh)(PPh3)2] and a cationic complex trans-[(PhCO)PdS(PPh3)2]+ (S = DMF) showing that the decarbonylation process is highly endergonic. The exchange of PPh3 by the bidentate ligand dppp does not favor the decarbonylation process.
The trans influence of F, Cl, Br and I ligands in a series of square-planar Pd(II) complexes. Relative affinities of halide anions for the metal centre in trans-[(Ph3P)2Pd(Ph)X]
Flemming, Jeffrey P.,Pilon, Mark C.,Borbulevitch, Oleg Ya.,Antipin, Mikhail Yu.,Grushin, Vladimir V.
, p. 87 - 98 (2008/10/08)
Single crystal X-ray diffraction studies of trans-[(Ph3P)2Pd(Ph)X] (X = F (1), Cl (2), Br (3), and I (4)) were carried out. The four structures split in two isostructural and isomorphous groups, namely orthorhombic for 1 and 2 (space group Pbca, Z = 8) and triclinic for 3 and 4 (space group P-1, Z=2). According to the Pd-C bond length, the trans influence of X within these pairs follows the trend Cl > F and I > Br. However, the trans influence of Cl is slightly stronger than that of Br. Both structural and 13C NMR studies revealed that electron-donating effects of (Ph3P)2PdX increase along the series X = I - for the Pd centre in [(Ph3P)2Pd(Ph)]+ were studied by 31P NMR in rigorously anhydrous CH2Cl2 solutions, and equilibrium constants and ΔG values were obtained for all possible combinations. The sequence F- > Cl- > Br- > I- is characteristic of halide preference for the Pd complexes. Dissolving 1 and PPN Cl in dry CH2Cl2 resulted in the release of 'naked' F- which fluorinated the solvent smoothly to give a mixture of CH2ClF and CH2F2 in high yield. When chloroform was used instead of CH2Cl2, dichlorocarbene was generated slowly, forming the corresponding cyclopropane in the presence of styrene. All observations were rationalized successfully in terms of the filled/filled effect and push/pull interactions.
