In Situ Generation of Carboxylate: An Efficient Strategy for a One-Pot Synthesis of Homo- and Heterometallic Polynuclear Complexes

An efficient strategy for synthesis of a wide range of homo- and heterometallic polynuclear
complexes is proposed. The synthesis protocol consists of a two-step one-pot reaction. The first step is
the in situ generation of carboxylate anions via oxidation of aromatic aldehydes by metal nitrates in air.
The aldehydes act as solvents and are also involved in redox processes. Solutions containing solely transition
metal cations and aromatic carboxylates are obtained following this procedure. The second step is a tunable
“à la carte” formation of a series of various polynuclear carboxylato complexes from solutions obtained at
the former stage upon addition of different solvents. The polarity and donor properties of the solvents play
a key role in determination of the nuclearities of the complexes. Hydrolytic processes can induce the
formation of oxo- or hydroxo-bridges inside the polynuclear core as well. Complexes of various nuclearities
are obtained:  from discrete tri-, hexa-, or octanuclear units to 1D polymers. This protocol can be adapted
with disconcerting simplicity to the synthesis of heterometallic species with similar molecular structures to
their homometallic analogues starting from stoichiometric mixture of metal nitrates under the same reaction
conditions. Detailed description of synthesis and the molecular structure of one representative complex for
each series are presented in this paper. The temperature dependence of magnetic susceptibility of the
heterometallic 1-D MnCo chain reveals typical behavior of a ferrimagnetic chain. The low-temperature
investigations on single crystals show significant Ising type magnetic anisotropy.