LANTHANOID COMPLEXES OF A TRIPODAL ACETAL LIGAND - SYNTHESIS, STRUCTURAL CHARACTERIZATION AND REACTIVITY WITH 3D METALS

A novel tripodal ligand (H(3)L(1)) has been prepared by condensation o f tris(2-aminoethyl)amine with 2,6-diformyl-4-methylphenol in MeOH. Th e compound has three equivalent side-arms, each containing four possib le ;donor groups, an imine N atom, a phenol O atom and two O-donors fr om an acetal group. The crystal structure showed the arms to be arrang ed such that a non-crystallographic three-fold axis passes through the bridgehead N atom. Reaction of H(3)L(1) with lanthanoid perchlorate s alts resulted in the isolation of two series of complexes. With early lanthanoids compounds of stoichiometry [Ln(H(3)L(1))(H2O)][ClO4](3) we re obtained and the compounds with Ln = La and Pr have been structural ly characterised. The lanthanoid site in these complexes is ten co-ord inate, with a geometry which can be related to an icosahedron. For lat er lanthanoids, complexes of stoichiometry [Ln(H(3)L(1))][ClO4], are f ound in which the lanthanoid site is nine-co-cordinate, with a tricapp ed trigonal-prismatic geometry. The complex with Ln = Y has been chara cterised by diffraction techniques. Mass spectroscopic studies indicat ed that the acetal functions within H(3)L(1) are stabilised by co-ordi nation to the lanthanoid metals. Reaction of the complex [La(H(3)L(1)) (H2O)][ClO4](3) with nickel(II) perchlorate led to a novel heterobimet allic complex in which both La and Ni are encapsulated within the trip odal ligand.