Synthesis and characterization of fluorophenylpalladium pincer complexes: electronic properties of some pincer ligands evaluated by multinuclear NMR spectroscopy and electrochemical studies

Abstract

Palladium fluorophenyl complexes with different pincer ligands Pd(Ar)[2,6-(tBu₂PCH₂)₂C₆H₃] (13), Pd(Ar)[2,6-(tBu₂PO)₂C₆H₃] (14), Pd(Ar)[{2,5-(tBu₂PCH₂)₂C₅H₂}Fe(C₅H₅)] (15), and Pd(Ar)[{2,5-(tBu₂PCH₂)₂C₅H₂}Ru(C₅H₅)] (16) were synthesized by the reaction of LiAr (Ar = C₆H₄F-4) with the respective trifluoroacetate palladium pincer complexes 9–12. The molecular structures of 14 and 16 were determined by an X-ray crystallographic method. Complexes 13–16 and {Pd(Ar)[{2,5-(tBu₂PCH₂)₂C₅H₂}Fe(C₅H₅)]}PF₆ (17) were studied by multinuclear NMR spectroscopy and cyclic voltammetry. On the basis of ¹⁹F NMR chemical shifts and ¹J(¹³C–¹⁹F) coupling constants, as well as Pd^II/Pd^IV oxidation potentials, electronic characteristics of the corresponding pincer ligands were elucidated.