Tetraselena crown ethers: synthesis and complexation with mercury salts. Crystal structure of a macrocycle and a mercury(II) complex

Abstract

Dipotassium benzene-1,2-diselenolate, C ₆ H ₄ (SeK) ₂ -1,2 obtained from the reaction of potassium tert-butoxide with a (benzene-1,2-diselenolato)zirconocene, was treated with C ₆ H ₄ [SeCH ₂ (CH ₂ OCH ₂ ) _n CH ₂ X] ₂ -1,2 (X = Cl, n = 1 1, n = 2 2, n = 3 3 or X = Br n = 3 4) leading to tetraselenacrown ethers C ₆ H ₄ [SeCH ₂ (CH ₂ OCH ₂ ) _n CH ₂ Se] ₂ C ₆ H ₄ (n = 1 6, n = 2 7 or n = 3 8) in a moderate yield (10–20%). This yield can be increased by using the ‘caesium effect' from benzene-1,2-diselenol (18–40%). These macrocyclic compounds are able to complex heavy metals [especially mercury(II) ions] via their selenium atoms. The mercury complexes have been characterized by multinuclear NMR spectroscopy. The molecular structures of the tetraselenacrown ether 7 and the mercury complex of macrocycle 8 have been established by X-ray diffraction.