Unusual binding of exogenous anions in some lead(II) complexes with a functionalized macrocycle

The potentially hexadentate compound 1,4,7-tris(pyrazol-1-ylmethyl)-1,4,7-triazacyclononane (L) gave the complexes [{PbL(O2CMe)}2][BPh4]2·2EtOH 1, [PbL(ClO4)]ClO42 and [PbL(BPh4)]BPh43. The crystal structures of the three complexes have been determined by single-crystal X-ray diffraction. In all, the lead(II) ion is co-ordinated by the six nitrogen donors of the ligand and is bound in addition by three oxygen atoms from bridging acetate (1) or perchlorate (2) anions, or interacts at a large distance with all the carbon atoms of a phenyl group from a tetraphenylborate anion (3). The access to the metal by the exogenous anions is allowed by the co-ordination requirements of the large lead(II) ion which cannot be completely satisfied by the flexible L ligand.