NEW TRANSITION METAL CLUSTERS WITH S, SE, AND TE ATOMS AS LIGANDS

D. Fenske, Paloma Sevillano, T. Langetepe, N. Zhu

There are a number of metal chalcogenide ions known in the gas phase. Examples are [Cu_2n+1E_n]^- (E: S, Se), [Ag_2n+1S_n]^- and [Ni_xS_y]^- clusters. Obviously it is possible to stabilize these species with protecting PR₃ ligands. Ab initio calculations show that the influence of the tertiary PR₃ ligands depends on the cluster size and type of the PR₃ ligand used. An easy route to such compounds is via the reaction of transition metal halides with silylated derivatives of S and Se. Examples are [Cu₁₂Se₆(Pr₃)₈], [Cu₂₀Se₁₀(PR₃)₈], [Cu₂₆Se₁₃(PR₃)₁₄], [Cu₃₀Se₁₅(PR₃)₁₂], [Cu₄₄Se₂₂(PR₃)₁₂], [Cu₄₈Se₂₂(PR₃)₂₀], [Cu₅₉Se₃₀(PR₃)₁₅], [Ag₁₁₂Se₃₂(SeBu)₄₈(PBu₃)₁₂], [Ag₁₇₂Se₄₀(SeBu)₉₂(dppp)₄] and many other clusters. During the last time we were also able to synthesize Au Clusters with up to 90 Au atoms. Examples are ionic clusters like: [Au₁₀Se₄(dppe)₄Br₂], [Au₁₈Se₈(dppe)₆Br₂], [Au₃₄Se₁₄(tpep)₆(tpepSe)₂Cl₆]. These compounds show interesting photophysical properties. These materials may be regarded as sections cut out of the structure of binary phases which are effectively shielded by an envelope of PR₃ ligands. The structures, properties and results from ab initio calculations will be reported. The conductivity is strongly dependent on the cluster size. Under high vacuum conditions the PR₃ ligands can be removed from the cluster surface. This results in the formation of an amorphous nano composite material. The size of the particles is between 3.0 to 5.0 nm with a very narrow size.