Molecular and electronic structures of one-electron oxidized NiII–(dithiosalicylidenediamine) complexes: NiIII–thiolate versus NiII–thiyl radical states

Stenson, P. A., Board, A., Marin-Becerra, A., Blake, A. J., Davies, E. S., Wilson, C. , McMaster, J. and Schröder, M. (2008) Molecular and electronic structures of one-electron oxidized NiII–(dithiosalicylidenediamine) complexes: NiIII–thiolate versus NiII–thiyl radical states. Chemistry: A European Journal, 14(8), pp. 2564-2576. (doi: 10.1002/chem.200701108) (PMID:18213560)

Abstract

The dithiosalicylidenediamine NiII complexes [Ni(L)] (R=tBu, R′=CH2C(CH3)2CH2 1, R′=C6H4 2; R=H, R′=CH2C(CH3)2CH2 3, R′=C6H4 4) have been prepared by transmetallation of the tetrahedral complexes [Zn(L)] (R=tBu, R′=CH2C(CH3)2CH2 7, R′=C6H4 8; R=H, R′=CH2C(CH3)2CH2 9, R′=C6H4 10) formed by condensation of 2,4‐di‐R‐thiosalicylaldehyde with diamines H2N‐R′‐NH2 in the presence of ZnII salts. The diamagnetic mononuclear complexes [Ni(L)] show a distorted square‐planar N2S2 coordination environment and have been characterized by 1H‐ and 13C 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 tBu 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 % HClO4. 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 NiIII centers. Species 2+ dimerizes at low temperature, and an X‐ray crystallographic determination of the dimer [(2)2](ClO4)2⋅2 CH2Cl2 confirms that this dimerization involves the formation of a S-S bond (S⋅⋅⋅S=2.202(5) Å).

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Wilson, Dr Claire
• Authors: Stenson, P. A., Board, A., Marin-Becerra, A., Blake, A. J., Davies, E. S., Wilson, C., McMaster, J., and Schröder, M.
• College/School: College of Science and Engineering > School of Chemistry
• Journal Name: Chemistry: A European Journal
• Publisher: Wiley
• ISSN: 0947-6539
• ISSN (Online): 1521-3765
• Published Online: 21 January 2008