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)].