Weakly binding azide ligands have been used as surface caps in the synthesis of lanthanide oxo and selenido clusters. Addition of NaN3 and Na2O to in situ prepared solutions of Ln(SePh)(3) in pyridine results in the formation of (py)(18)Sm6Na2O2(N-3)(16) or (py)(10)Ln(6)O(2)(N-3)(12)(SePh)(2) (Ln = Ho, Er), with the Sm and Er compounds characterized by low temperature single crystal X-ray diffraction. Attempts to prepare chalcogenido derivatives by ligand-based redox reactions using elemental Se were successful in the preparation of (py)(10)Er6O2(SeSe)(2)(N-3)(10), a diselenido cluster having crystallographic disorder due to some site sharing of both SeSe and N-3 ligands. These compounds all detonate when heated.