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Milsmann C, Bothe E, Bill E, Weyhermuller T, Wieghardt K: Octahedral Monodithiolene Complexes of Cobalt (III) and Chromium (III). Inorg Chem. 2009 May 11.
Spectroscopic and Density Functional Theoretical Characterization of S,S'-Coordinated Benzene-1,2-dithiolate (1-) pi Radicals.. The reaction of [M (tren) Cl (2)] Cl (M = Co (III), Cr (III)) with benzene-1,2-dithiol, H (2)(bdt), and 3,6-bis (trimethylsilyl) benzene-1,2-dithiol, H (2)(tmsdt), in a water/methanol mixture in the presence of potassium tert-butoxide produced green crystals of [M (tren)(bdt)](PF (6))(1/2)(Cl)(1/2).H (2) O (1 (PF (6))(1/2)(Cl)(1/2).H (2) O, M = Co; 2 (PF (6))(1/2)(Cl)(1/2).H (2) O, M = Cr) and [M (tren)(tmsdt)](PF (6))(1/2)(Cl)(1/2).H (2) O (1a (PF (6))(1/2)(Cl)(1/2).H (2) O, M = Co; 2a (PF (6))(1/2)(Cl)(1/2).H (2) O, M = Cr), respectively, upon addition of KPF (6). The structures of 1 (PF (6))(1/2)(Cl)(1/2).H (2) O and 2 (PF (6))(1/2)(Cl)(1/2).H (2) O have been determined by X-ray crystallography. Octahedral 1 and 1a are diamagnetic whereas 2 and 2a possess an S = (3)/(2) ground state. Cyclic voltammetry of 1a and 2a in CH (2) Cl (2) solution established that both species undergo a reversible one-electron oxidation generating the stable dications [Co (III)(tren)(tmsdt (*))](2+) (S = (1)/(2)) and [Cr (III)(tren)(tmsdt (*))](2+) (S = 1) where (tmsdt (*))(1-) represents the pi radical monoanion of oxidized (tmsdt)(2-). The electrochemical oxidations are ligand centered processes. These dications have been investigated by UV-vis and EPR spectroscopy and density functional calculations using the B3LYP functional. The S,S'-coordinated benzene-1,2-dithiolate (1-) radical has been identified and unambiguously characterized. Comparison with the corresponding o-benzosemiquinonate (1-) complexes shows that the S,S'-coordinated benzene-1,2-dithiolate (1-) radical is a sulfur centered radical whereas its oxygen containing analogue carries approximately 65% of the spin density on the six-membered ring. |
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