Chalcogen–chalcogen interactions in trichalcogenaferrocenophanes. Crystal structure of 2-selena-1,3-ditellura[3]ferrocenophane [Fe(C5H4Te)2Se]

The preparation, 77Se and 125Te NMR spectroscopic characterization, and crystal structure of 2-selena-1,3-ditellura[3]ferrocenophane [Fe(C5H4Te)2Se] have been reported. The complex crystallizes in a triclinic crystal system with the space group P 1 ¯ . The comparison of the X-ray structure of [Fe(C5H4Te)2Se] with those of other members in the [Fe(C5H4E)2E′] (E, E′ = S, Se, Te) series shows that the intermolecular chalcogen–chalcogen interactions are weak in case of sulfur or selenium, but become significant for interactions involving tellurium. This is consistent with the concept of secondary bonding interactions between the atoms of heavy main group elements.