A solution-state dipole moment and microwave dielectric loss study of Ti, Zr, Hf and Sn cyclopentadienyl compounds.

Abstract

Dielectric properties of cyclopentadienyl complexes Cp 2MX 2 and Cp 4M (M = Ti, Zr, Hf or Sn; X = Cl or Br; Cp = cyclopentadienyl) have been investigated in dilute benzene or 1,4-dioxane solution using the standard refractivity and microwave dielectric absorption techniques. The highly dipolar nature of the molecules Cp 2MX 2 has been confirmed for the solution-state and it has been shown that atomic distortion polarisalions for these compounds are small. The dielectric relaxation times for the Cp 2MX 2 molecules are consistent with a process of overall molecular tumbling. The compounds Cp 4Zr and Cp 4Hf are also highly dipolar indicating non-equivalent Cp rings about the metal. The predominant component of dielectric relaxation for these is by molecular tumbling although weakly absorbing intramolecular modes must also exist. The complex Cp 4Sn has a low dipole moment and is weakly absorbing, this being consistent with a (η 1-Cp) 4Sn structure.