54866-11-4Relevant academic research and scientific papers
Transmetalation of arylpalladium and platinum complexes. Mechanism and factors to control the reaction
Suzaki, Yuji,Yagyu, Takeyoshi,Osakada, Kohtaro
, p. 326 - 342 (2008/02/03)
This article reviews recent studies on intra- and intermolecular transfer of the aryl ligand bonded to Pd(II) and Pt(II). Cationic arylpalladium complexes with bpy and THF ligands undergo intermolecular aryl group transfer to produce biaryl via a diarylpalladium intermediate. This reaction is applied to cyclization of cationic dinuclear arylpalladium complexes, affording the crown ether derivative with biphenylene units. Analogous arylplatinum complexes do not form diaryl complexes via transmetalation, while they react with CO and phenylallene to cause replacement of the coordinated solvent and insertion of the small molecules into the Pt-C bond, respectively. Conproportionation of PtCl2(cod) and PtPh2(cod) produces PtCl(Ph)(cod), which is induced by dissociation of a Cl ligand from the former complex. PtCl2(cod) reacts also with diarylplatinum complexes with bpy and dppe. Disproportionation of PtPh(CH2COMe)(cod) and conproportionation of PtPh2(cod) and Pt(CH2COMe)2(cod) take place at 50 °C, but the rates of apparently reversible reactions differ from each other. Addition of OH- to a solution of PtI(Ph)(cod) causes intermolecular phenyl ligand transfer to produce PtPh2(cod). The dinuclear intermediate complex with bridging OH ligand is prepared from an independent route and fully characterized. The complex causes transmetalation of aryl group of aryl boronic acid.
Distinct electronic effects on reductive eliminations of symmetrical and unsymmetrical bis-aryl platinum complexes
Shekhar, Shashank,Hartwig, John F.
, p. 13016 - 13027 (2007/10/03)
Symmetrical bis-aryl platinum complexes (DPPF)Pt(C6H 4-4-R)2 (R = NMe2, OMe, CH3, H, Cl, CF3) and electronically unsymmetrical bis-aryl platinum complexes (DPPF)Pt(C6H4-R)(C6H4-4-X) (R = CH3, X = NMe2, OMe, H, Cl, F, CF3; R = OMe, X = NMe2, H, Cl, F, CF3; R = CF3, X = H, Cl, NMe2; and R = NMe2, X = H, Cl) were prepared, and the rates of reductive elimination of these complexes in the presence of excess PPh3 are reported. The platinum complexes reductively eliminated biaryl compounds in quantitative yields with first-order rate constants that were independent of the concentration of PPh3. Plots of Log(k obs/kobs(H)) vs Hammett substituent constants (σ) of the para substituents R and X showed that the rates of reductive elimination reactions depended on two different electronic properties. The reductive elimination from symmetrical bis-aryl platinum complexes occurred faster from complexes with more electron-donating para substituents R. However, reductive elimination from a series of electronically unsymmetrical bis-aryl complexes was not faster from complexes with the more electron-donating substituents. Instead, reductive elimination was faster from complexes with a larger difference in the electronic properties of the substituents on the two platinum-bound aryl groups. The two electronic effects can complement or cancel each other. Thus, this combination of electronic effects gives rise to complex, but now more interpretable, free energy relationships for reductive elimination.
