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)(2)NMe2 = L-1, CH=N(CH2)(2)NMe2 = L-2, and CH2NH(CH2)(2)NMe2 = L-3). Dizinc trihalide complexes [(LZn2)-Zn-n(mu-X)X-2] (where X = CI, Br, I) have been prepared. The trihalide complexes were treated with potassium ethoxide, resulting in quantitative substitution of the bridging halide group to give [(LZn2)-Zn-n(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 [(LZn2)-Zn-n(OAc)(3)], as well as cationic diacetate species containing two bridging acetate groups, [(LZn2)-Zn-n(mu-OAc)(2)][BPh4]. Structural differences between completes of the three ligands are discussed.