Dipole-moment measurements on metal chelate complexes. Part 4. The effect of substitution in the phenyl ring on the dipole moments of metal chelates of fluorinated mercapto-β-diketones containing a phenyl group

Abstract

Dipole moments have been determined from static-polarization measurements for the nickel(II), palladium(II), platinum(II), copper(II) zinc(II), cobalt(III), and rhodium(III) chelate complexes of the fluorinated mercapto-β-diketones RC(SH):CHCOCF₃[R =p-MeOC₆H₄, m-MeOC₆H₄, m,p-(MeO)₂C₆H₃, and m,p-Me₂C₆H₃]. The moments indicate cis-square-planar conformations for the complexes of Ni, Pd, Pt, and Cu, and a facial-octahedral configuration for those of Co and Rh. For all the metal complexes with methyl substitution of the phenyl ring the dipole moments decrease if the R groups are arranged in the order: m,p-Me₂C₆H₄ > p-MeC₆H₃ > m-MeC₆H₄ > Ph. However, for methoxy-substitution the order is: p-MeOC₆H₄ > m,p-(MeO)₂C₆H₃ > Ph. The anomalous position of m,p-(MeO)₂C₆H₃is ascribed to steric hindrance preventing free rotation of the methoxy-groups and leading to a lower group moment µ_R–ch.