Abstract
The dithiosalicylidenediamine Ni^II^ complexes [Ni(L)] (R=__t__Bu, R′=CH~2~C(CH~3~)~2~CH~2~ 1, R′=C~6~H~4~ 2; R=H, R′=CH~2~C(CH~3~)~2~CH~2~ 3, R′=C~6~H~4~ 4) have been prepared by transmetallation of the tetrahedral complexes [Zn(L)] (R=__t__Bu, R′=CH~2~C(CH~3~)~2~CH~2~ 7, R′=C~6~H~4~ 8; R=H, R′=CH~2~C(CH~3~)~2~CH~2~ 9, R′=C~6~H~4~ 10) formed by condensation of 2,4‐di‐R‐thiosalicylaldehyde with diamines H~2~N‐R′‐NH~2~ in the presence of Zn^II^ salts. The diamagnetic mononuclear complexes [Ni(L)] show a distorted square‐planar N~2~S~2~ coordination environment and have been characterized by ^1^H‐ and ^13^C NMR and UV/Vis spectroscopies and by single‐crystal X‐ray crystallography. Cyclic voltammetry and coulombic measurements have established that complexes 1 and 2, incorporating __t__Bu functionalities on the thiophenolate ligands, undergo reversible one‐electron oxidation processes, whereas the analogous redox processes for complexes 3 and 4 are not reversible. The one‐electron oxidized species, 1^+^ and 2^+^, can be generated quantitatively either electrochemically or chemically with 70 % HClO~4~. EPR and UV/Vis spectroscopic studies and supporting DFT calculations suggest that the SOMOs of 1^+^ and 2^+^ possess thiyl radical character, whereas those of 1(py)~2~^+^ and 2(py)~2~^+^ possess formal Ni^III^ centers. Species 2^+^ dimerizes at low temperature, and an X‐ray crystallographic determination of the dimer (2)~2~~2~⋅2 CH~2~Cl~2~ confirms that this dimerization involves the formation of a SS bond (S⋅⋅⋅S=2.202(5) Å).