Nickel(II) Complexes with Dithiadiiminoamine and Dithiabis(thiosemicarbazone) Ligands

4,7-Dithiadecane-2,9-dione (Dtdk) serves as a starting point for generation of multidentate nitrogen/sulfur chelating agents. Condensation with ethylenediamine or diethylenetriamine yields the neutral hexadentate ligands 1,14-diamino-4,11-dimethyl-6,9-dithia-3,12-diazatetradeca-3,11-diene (Dtdida) and 15-amino-9-methyl-4,7-dithia-10,13-diazapentadec-9-en-2-one (Dtidak) respectively, while the diketone\u27s bis(thiosemicarbazone), itself a neutral ligand, may be deprotonated to form the hexadentate dianion Dtdtz2-. Blue/violet nickel(II) complexes with these ligands have been prepared, viz. Ni(Dtdida)(CIO4)2·0.5H2O 1, Ni(Dtidak)(ClO4)2·0.5CH3CN 4, Ni(DtdtzH2)(ClO4)2 2, and Ni(Dtdtz) 3; they are all S = 1 pseudo-octahedral systems. Although diamines such as ethylenediamine or diethylenetriamine are in principle capable of forming macrocyclic ligands with Dtdk, the products obtained were acyclic. In the case of Ni(Dtidak)2+, a keto-group and a primary amine residue co-exist within the cation, entailing an unusual example of a complex with a non-conjugated ketone coordinated to nickel(II). The coordination spheres of all four complexes have parallel N2S2X2 donor sets, with the ligands similarly folded. The properties of Ni(Dtdtz) evidence significant contribution from the imino-thiolate resonance form of the thioamide moiety. One consequence of this is the relative facility of oxidation of Ni(Dtdtz) to the nickel(III) form, at +0.24 V vs. SCE. © The Royal Society of Chemistry 2000