Dinuclear Zinc Complexes Using Pentadentate Phenolate Ligands

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 CH2NMe(CH2)2NMe2 = L1, CHN(CH2)2NMe2 = L2, and CH2NH(CH2)2NMe2 = L3). Dizinc trihalide complexes [LnZn2(μ-X)X2] (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 [LnZn2(μ-OEt)X2]. The dizinc ethoxide complexes were tested in situ as initiators for lactide ring opening polymerization. Dizinc triacetate complexes have also been synthesized [LnZn2(OAc)3], as well as cationic diacetate species containing two bridging acetate groups, [LnZn2(μ-OAc)2][BPh4]. Structural differences between complexes of the three ligands are discussed.