160299-35-4Relevant academic research and scientific papers
Divalent palladium and platinum complexes containing rigid bidentate nitrogen ligands and electrochemistry of the palladium complexes
Van Asselt, Rob,Elsevier, Cornelis J.,Amatore, Christian,Jutand, Anny
, p. 317 - 328 (1997)
The synthesis and characterization of divalent palladium and platinum complexes of the type PdX2(Ar-BIAN) (X = Cl, Br, I, OC(O)Me), PdCl2(Ph-BIC) and PtCl2(Ar-BIAN) is described. These complexes contain the rigid bidentate nitrogen ligands bis(arylimino)-acenaphthene (Ar-BIAN; Ar = Ph, p-MeC6H4, p-MeOC6H4, o,o′-Me2C6H3, o,o′-i-Pr2C6H3) or bis(phenylimino)camphane (Ph-BIC), which act as σ-donor ligands to the metal center, as was deduced from the observed shifts in the IR and NMR spectra of the complexes. Electrochemical reduction of PdCl2(Ar-BIAN) complexes in THF or DMF occurs via two one-electron reductions and affords the complex PdICl(Ar-BIAN).-, which slowly produces some Pd0(Ar-BIAN) complex. PdICl(Ar-BIAN).- reacts with iodomethane, whereas with iodobenzene or bromobenzene no reaction was observed. PdICl(Ar-BIAN).- reacts with free Ar-BIAN or the alkenes dimethyl fumarate, dimethyl maleate, and methyl acrylate, giving complexes of the formulas PdICl(Ar-BIAN)2.- and PdICl(Ar-BIAN)(alkene).-, respectively. A two-electron reduction of the latter afforded Pd0(Ar-BIAN)22- and Pd0(Ar-BIAN)(alkene)2-, respectively, whose further oxidation in two one-electron steps produces Pd0(Ar-BIAN)2 and Pd0(Ar-BIAN)(alkene). The Pd0(Ar-BIAN) complex which is slowly formed from PdICl(Ar-BIAN).- reacts with alkene but directly affords the complexes Pd0(Ar-BIAN)(alkene).- because Pd0(Ar-BIAN)(alkene) complexes are formed at a potential more negative than their first reduction potential. Reoxidation of Pd0(Ar-BIAN)(alkene).- affords Pd0(Ar-BIAN)(alkene) complexes. The results of the electrochemical experiments corroborate earlier mechanistic proposals of exchange of Ar-BIAN ligands in Pd0(Ar-BIAN)(alkene) complexes and homogeneous hydrogenation of electron-poor alkenes by Pd0(Ar-BIAN)(alkene) complexes.
