Application of a universal force field to mixed Fe/Mo-S/Se cubane and heterocubane clusters. 2. Substitution of iron by molybdenum in Fe4(S/Se)4 clusters with terminal halide and thiolate ligands.

Abstract

Infrared and Raman spectra of Fe(4)(S/Se)(4) clusters with terminal halide ligands and MoFe(3)S(4) clusters with terminal thiolate and halide ligands are presented and interpreted on the basis of the force fields determined in the accompanying paper. The Raman spectra of halide coordinated Fe(4)(S/Se)(4) clusters are characterized by the fact that vibrations of the terminal ligands appear with little or vanishing intensity. Infrared and Raman spectra of MoFe(3)S(4) clusters with terminal thiolates are correlated to those of corresponding Fe(4)S(4) systems, which were investigated in part 1 of this study and interpreted with normal coordinate analysis. Band assignments are checked by employing MoFeS(4) clusters with terminal halide ligands. Spectra of these systems are in turn compared to those of their Fe(4)S(4) counterparts, i.e., Fe-S cubane clusters with chloro, bromo, and iodo ligands. A consistent interpretation of all spectra is presented. General implications of these results are discussed.