Controlled synthesis and reversible oxidation of a thiolate-bridged macrocyclic dinickel(II) complex

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Abstract
The synthesis of S-(2,6-Diformyl-4-methylphenyl) dimethylthiocarbamate, a valuable thiolate-containing ligand precursor, is reported in detail for the first time. This precursor has considerable potential in biosite modelling studies. A macrocycle L and a related acyclic ligand L′ have been prepared, as complexes, from the precursor and 1,3-diaminopropane. The macrocycle was successfully templated by both zinc(II) and nickel(II) ions yielding [Zn2L(H2O)2][O3SCF3]2·H2O 1 and the diamagnetic complex [Ni2L][ClO4]22, respectively. A single-crystal X-ray analysis of 1 showed the zinc ions to have trigonal-bipyramidal environments and the macrocycle to have a stepped conformation. In contrast, the structure determination of 2 revealed square-planar N2S2 co-ordination for NiII and a bowed macrocycle conformation which results in much shorter metal–metal and sulfur–sulfur separations than the stepped conformation adopted in the case of ZnII[average Zn Zn 3.351(1), S S 3.363(3) for 1vs. Ni Ni 3.146(2), S S 2.839(5)Å for 2]. Two one-electron oxidations, the first reversible and the second quasi-reversible, were observed for the dinickel(II) complex, whereas one irreversible two-electron oxidation was observed for the dizinc(II) complex. An acetal forms in the presence of ethanol and leads to the isolation of the acyclic trinickel(II) complex [Ni2L′2Ni][ClO4]23.

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