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 pyri dine to give (pyridine)(g)Yb-4(SeSe)(2)(Se)(2)(mu (2)-SPh)(2)(SPh)(2), (py) (8)Yb4Se(SeSe)(3)(SeSeSePh)(Se0.38SePh), and (py)(8)Yb4Se(ScSe)(3)-(SeSeTeP h)(SeTePh), respectively. The SePh and TePh compounds contain a square arra y of Ln(III) ions all connected to a central Se2- ligand. Three edges of th e square are bridged by diselenide ligands, with the fourth SeSe unit coord inating to an EPh ligand that has been displaced from an inner Yb coordinat ion sphere. Differences in the two compounds have their origin in the relat ive strength of the Yb-E(Ph) bond. In the TePh compound, there is a complet e insertion of Se into the remaining Yb-Te(Ph) bond to give a terminal SeTe Ph ligand, while in the SePh compound there is a compositional disorder in the structure comprised of a terminal SePh ligand and a minor component tha t has Se inserted into the Yb-Se(Ph) bond to give a terminal SeSePh ligand. The thiolate compound differs dramatically, crystallizing as a rhombohedra l array of four Yb(III) ions connected by a pair of mu (3)-Se2- ligands, wi th the edges of the rhombus spanned by alternating diselenide and SPh. The SPh coordinate directly to Yb(III) ions in terminal or bridging modes. Clus ter interconversion is facile: (py)(4)Yb(SePh)(2) reduces (py)(8)Yb4Se(SeSe )(3)(SeSeSePh)(Se0.38SePh) to give the cubane cluster [(py)(2)YbSe(SePh)](4 ), and the cubane reacts with elemental Se to give (py)(8)Yb4Se(SeSe)(3)(Se SeSePh)(Se0.38SePh). Upon thermolysis, these compounds give YbSex.