Single-crystal Raman study of some aquo-pentachloro-salts [MCl5-(H2O)]2–(M = In or Fe)

Abstract

Raman single-crystal spectra are reported for eight hydrates and deuteriates [MCl₅(H₂O)]^2–(M = In or Fe). Many fewer lattice modes were found than predicted, but for the anion internal modes factor-group predictions accord well with observation. A complete assignment in terms of anion C_4v symmetry is deduced. Deuteriation enabled identification of all skeletal modes associated with oxygen-atom motions. The most unusual feature of the assignments is that π(MCl₄) modes come above δ(MCl₄) modes. Comparison with single-crystal assignments for [InCl₅]^2– show that the largest change is in the A₁π(InCl₄) mode which is raised upon aquation of the complex.