Pentafluorophenyl derivatives of transition metals. Part VI. Nuclear magnetic resonance spectra of some nickel, palladium, and platinum complexes

Abstract

The fluorine and the proton n.m.r. spectra of several pentafluorophenyl complexes of nickel, palladium, and platinum have been studied. A relatively large shift to low field was observed for the ortho-fluorine nuclei of the pentafluorophenyl groups. In the trans-isomers of [(C₂H₅)₃P]₂Pt(C₅F₆)X an attempt was made to relate chemical-shift differences between para- and meta-fluorine atoms to the presumed π-bonding characteristics of the ligand X. The observed platinum–fluorine coupling constants are large, and are a function of the nature of X, increasing in the sequence CH₃ < CN < NO₂ < I ∼ NCS < Br < Cl < ONO₂, i.e., in the reverse order to the trans-directing ability of these ligands. By measuring proton n.m.r. spectra and using the virtual coupling concept, the stereochemistry of several of the complexes, previously established by other methods, has been confirmed. Several coupling constants of interest are reported. The synthesis of some new pentafluorophenyl-metal complexes is described.