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 µR–ch.