Compartmental pyrazolate ligands providing two adjacent tris(pyridylalkyl)amine-type binding pockets and their dicopper(II) fluoride complexes featuring extremely short intramolecular O-H•••F bridge

A set of pyrazolate-based compartmental ligands HL2-HL5 with pendent (pyridylalkyl)amine side arms in the 3- and 5-positions of the pyrazole has been prepared. The ligands differ by the number and lengths of the pyridylalkyl arms, and they can be described as dinucleating versions of well-known ligands such as tris(pyridylmethyl)amine (tpma) or tris(pyridylethyl)amine (tpea). Reaction of HL2, HL3 or HL5 with Cu(BF4)(2).6H(2)O in the presence of base causes fluoride abstraction from the tetrafluoroborate and gives dicopper(II) complexes 1, 2, and 3a and b, respectively, which feature extremely short intramolecular F...HOMe or F...HOH bridges (d(F...O) = 2.384(6)-2.507(3)). Molecular structures of all four complexes have been elucidated by X-ray crystallography and are compared to their mononuclear analogues. The influence of the intramolecular F...HO bridge on Cu F and Cu-O bond lengths as well as on other structural characteristics is discussed. (C) 2004 Elsevier B.V. All rights reserved.