The first example of a complex of N-perfluoroarylated azacrown ether: The crystal structure of diaqua{N,N′-bis(tetrafluoropyridyl)diaza-18-crown-6}lead(II) perchlorate

Abstract

Complex formation of lead(II) perchlorate with N,N′-diaryldiaza-18-crown-6 (aryl = C6H5, 4-MeOC6H4, 4-C5F4N) has been studied. The stability of the complexes decreases with an increase in the electron-withdrawing character of the aryl substituent in the series (logβ, methanol): 4-MeOC6H4 (4.7), C6H5 (2.7), 4-C5F4N ( 2σ(I). In the complex cation [Pb(L)(H2O)2]2+, the coordination geometry of the metal atom is determined by partial delocalization of the lone pair. The Pb atom is asymmetrically bound to four oxygen atoms of substituted diaza-18-crown-6 and two oxygen atoms of water molecules (Pb-O, 2.450–2.726 A). The CN of the metal atom is completed to ten by two nitrogen atoms of the macrocycle and two ortho fluorine atoms of two tetrafluoropyridyl substituents of the ligand L at longer distances (Pb-N, 2.978 and 3.108 A; Pb-F, 2.890 and 3.123 A).