Dinuclear Zinc Complexes Using Pentadentate Phenolate Ligands

Abstract

The synthesis and characterization of 15 dinuclear zinc complexes are reported, including the X-ray crystal structures of 5 complexes. The ligand motif utilizing p-cresol as a bridging unit between the two zinc centers and a set of three related ligands has been synthesized; 2,6-bis(R)-p-cresol (where R is CH(2)NMe(CH(2))(2)NMe(2) = L(1), CH=N(CH(2))(2)NMe(2) = L(2), and CH(2)NH(CH(2))(2)NMe(2) = L(3)). Dizinc trihalide complexes [L(n)Zn(2)(mu-X)X(2)] (where X = Cl, Br, I) have been prepared. The trihalide complexes were treated with potassium ethoxide, resulting in quantitative substitution of the bridging halide group to give [L(n)Zn(2)(mu-OEt)X(2)]. The dizinc ethoxide complexes were tested in situ as initiators for lactide ring opening polymerization. Dizinc triacetate complexes have also been synthesized [L(n)Zn(2)(OAc)(3)], as well as cationic diacetate species containing two bridging acetate groups, [L(n)Zn(2)(mu-OAc)(2)][BPh(4)]. Structural differences between complexes of the three ligands are discussed.