Trivalent Lanthanide Chalcogenolates: Synthesis, Structure, and Thermolysis Chemistry

Lanthanide-mercury amalgams react with diphenyl diselenide to form tris(benzeneselenolates) that can be isolated as the crystalline pyridine coordination complexes (pyridine)₃Ln(SePh)₃ (Ln = Ho (1), Tm (2), Yb (3)). The structure of 2 was established by low temperature single crystal X-ray diffraction. The complex is dimeric in the solid state, with 7-coordinate metal centers connected by a pair of μ₂-(benzeneselenolate) ligands. Thermal decomposition of the selenolates gives a variety of solid state metal selenides: 1 gives HoSe, HoSe₂, and Ph₂Se; 2 gives Tm₂Se₃ and Ph₂Se; 3 gives Yb₂Se₃ and Ph₂Se. Trivalent thiolates can also be prepared by this amalgam reaction. For comparison, the structure of Yb(SPh)₃(pyridine)₃ (4) was also determined-4 is a monomelic mer-octahedral compound with inequivalent Yb-S bonds. Both 3 and 4 have an intense visible chalcogen-to-ytterbium charge transfer absorption band. Crystal data (Mo Ka, 153(2) K) are as follows. 2: Triclinic space group P1, a = 10.435(2) Å, b = 12.748(2) Å, c = 14.453(2) Å, α = 69.85(2)°, β = 80.71(2)°, and γ = 69.03(2)°. 4: Triclinic space group P1, a = 9.836(10) Å, b = 11.304(14) Å, c = 16.202(11) Å, α = 80.70°, β = 77.91(7)°, and γ = 68.34(9)°.