Structural Diversity of Ethylzinc Carboxylates

The synthesis and structural characterization of a new series of ethylzinc carboxylates are reported. Structurally diverse complexes were derived from three monofunctional carboxylic acids with different numbers of phenyl groups on the α-carbon, and two bifunctional carboxylic acids with a neutral donor terminus, namely, methoxyacetic and diethylphosphonoacetic acids. Donor solvents are commonly used in various transformations of alkylzinc carboxylates; therefore, the effect of THF as a donor solvent on the reaction outcome was also investigated. Reactions of equimolar amounts of Et2Zn and the selected carboxylic acid in THF solutions gave ethylzinc carboxylates with a large variety of structures. In the cases of triphenylacetic and diphenylacetic acids, THF solvated products of stoichiometry [EtZn­(O2CR)­(THF)] were isolated as a dimer and a 1D coordination polymer, respectively, whereas, with methoxyacetic acid, a novel solvent-free hexanuclear structural motif with a butterfly-like framework was formed, ([EtZnO2­CCH2OCH3]6). The corresponding reaction with diethylphosphonoacetic acid produced a rare example of a nonanuclear organozinc oxo carboxylate cluster, [(EtZn)8Zn­(μ3-O)2­(O2CCH2(O)­P­(OEt)6)].