Single-Crystal X-ray and Solution13C NMR Study of Fluoro(p-nitrophenyl)bis(triphenylphosphine)palladium(II). Are There Effects of Through-Conjugation?

The Pd−F and Pd−C bond distances in the X-ray structure of trans- fluoro( p -nitrophenyl)bis(triphenylphosphine)palladium(II), 1, are shorter by ca. 0.036 and 0.013 Å, respectively, than those in the analogous σ-phenyl complex, 2 . This structural feature along with the 13 C NMR spectral characteristics of 1 and its iodo counterpart indicates a contribution from the quinoid-type canonical form A to the structure of 1 . However, the geometry of the p -nitrophenyl ligand in 1 does not exhibit effects of through-conjugation, suggesting that the resonance effect of trans -[(Ph 3 P) 2 Pd(F)] is weaker than those of NH 2 and MeO.