Chalcogen-Rich Lanthanide Clusters: Cluster Reactivity and the Influence of Ancillary Ligands on Structure

Ytterbium metal reacts with PhEEPh (E = S, Se, Te) and elemental Se in pyridine to give
(pyridine)8Yb4(SeSe)2(Se)2(μ2-SPh)2(SPh)2, (py)8Yb4Se(SeSe)3(SeSeSePh)(Se0.38SePh), and (py)8Yb4Se(SeSe)3(SeSeTePh)(SeTePh), respectively. The SePh and TePh compounds contain a square array of Ln(III) ions all
connected to a central Se2- ligand. Three edges of the square are bridged by diselenide ligands, with the
fourth SeSe unit coordinating to an EPh ligand that has been displaced from an inner Yb coordination sphere.
Differences in the two compounds have their origin in the relative strength of the Yb−E(Ph) bond. In the
TePh compound, there is a complete insertion of Se into the remaining Yb−Te(Ph) bond to give a terminal
SeTePh ligand, while in the SePh compound there is a compositional disorder in the structure comprised of
a terminal SePh ligand and a minor component that has Se inserted into the Yb−Se(Ph) bond to give a terminal
SeSePh ligand. The thiolate compound differs dramatically, crystallizing as a rhombohedral array of four
Yb(III) ions connected by a pair of μ3-Se2- ligands, with the edges of the rhombus spanned by alternating
diselenide and SPh. The SPh coordinate directly to Yb(III) ions in terminal or bridging modes. Cluster
interconversion is facile:  (py)4Yb(SePh)2 reduces (py)8Yb4Se(SeSe)3(SeSeSePh)(Se0.38SePh) to give the cubane
cluster [(py)2YbSe(SePh)]4, and the cubane reacts with elemental Se to give (py)8Yb4Se(SeSe)3(SeSeSePh)(Se0.38SePh). Upon thermolysis, these compounds give YbSex.