Molecular and electronic structures of one-electron oxidized Ni(II)-(dithiosalicylidenediamine) complexes: Ni(III)-thiolate versus Ni(II)-thiyl radical states.
The dithiosalicylidenediamine Ni II 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 Zn II 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 Ni III 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) A).
Stenson
Philip A
PA
School of Chemistry, University of Nottingham, Nottingham, NG7 2RD, UK.
Board
Ashley
A
Marin-Becerra
Armando
A
Blake
Alexander J
AJ
Davies
E Stephen
ES
Wilson
Claire
C
McMaster
Jonathan
J
Schröder
Martin
M
D000588:Amines / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004563:Electrochemistry; D004578:Electron Spin Resonance Spectroscopy; D004583:Electrons; D005609:Free Radicals / Q000737:chemistry; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D009532:Nickel / Q000737:chemistry*; D010084:Oxidation-Reduction; D012459:Salicylates / Q000737:chemistry*; D013054:Spectrophotometry, Atomic; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry
D000588:Amines; D005609:Free Radicals; D008024:Ligands; D012459:Salicylates; D013438:Sulfhydryl Compounds; D009532:Nickel; D015032:Zinc