Octahedral Monodithiolene Complexes of Cobalt(III) and Chromium(III). Spectroscopic and Density Functional Theoretical Characterization of S, S'-Coordinated Benzene-1.2-dithiolate(1-)π Radicals.

The reaction of [M(tren)Cl[sub2]]Cl(M=Co(III), Cr(III)) with benzene-1,2-dithiol, H[sub2](dbt), and 3,6-bis(trimethylsilyl)benzene-1,2-dithiol, H[sub2](tmsdt), in a water/methanol mixture in the presence of potassium tert-butoxide produced green crystals of [M(tren)(bdt)](PF[sub6])[sub½](Cl)[sub½]∙H[sub2]O (1(PF[sub6])[sub½](Cl)[sub½]∙H[sub2]O, M = Co; 2(PF[sub6])[sub½]](Cl)[sub½]∙H[sub2]O, M = Cr) and [M(tren)(tmsdt)](PF[sub6])[sub½](CI)[sub½]∙H[sub2]O (1a(PF[sub6])[sub½](Cl)[sub½]∙H[sub2]O, M = Co; 2a(PF[sub6])[sub½](Cl)[sub½]∙H[sub2]O, M = Cr), respectively, upon addition of KPH[sub6]. The structures of 1(PF[sub6])[sub½](CI)[sub½]∙H[sub2]O and 2(PF[sub6])[sub½](CI)[sub½]∙H[sub2]O have been determined by X-ray crystallography. Octahedral 1 and 1a are diamagnetic whereas 2 and 2a possess an S=¾ ground state. Cyclic voltammetry of 1a and 2a in CH[sub2]Cl[sub2] solution established that both species undergo a reversible one-electron oxidation generating the stable dications [Co[supII](tren)(tmsdt[sup∙])][sup2+] (S=½) and [Cr[supIII](tren)(tmsdt[sup∙])][sup2+] (S=1) where (tmsdt[sup∙])[sup1-] represents the π radical monoanion of oxidized (tmsdt)[sup2-]. The electrochemical oxidations are ligand centered processes. These dictations have been investigated by UV-vis and EPR spectroscopy an d density functional calculations using the B3LYP functional. The S,S'-coordinated benzene-1,2-dithiolate(1-) radical has been identified and ambiguously 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 ∼65% of the spin density on the six-membered ring. [ABSTRACT FROM AUTHOR]