Square Planar Bis{3,6-bis(trimethylsilyl)benzene-1,2-dithiolato}metal Complexes of Cr^II, Co^III, and Rh^II: An Experimental and Density Functional Theoretical Study

The three square planar complexes [N(n-Bu)₄]₂[Cr^IIL₂]·4CH₃CN (S = 2; 1), [N(n-Bu)₄][Co^IIIL₂] (S = 1; 3), and [N(n-Bu)₄]₂[Rh^IIL₂]·4CH₃CN (S = ¹/₂; 4) have been prepared and structurally characterized by X-ray crystallography (L²⁻ represents the 3,6-bis(trimethylsilyl)benzene-1,2-dithiolate(2−)). Aerial oxidation of CH₂Cl₂ solutions of 1 produced purple crystals of [N(n-Bu)₄][Cr^VOL₂]·2CH₂Cl₂ (S = ¹/₂; 2), the structure of which has also been determined by X-ray crystallography. The electro- and magnetochemistry of all species has been studied. Their electronic structures have been experimentally investigated by recording their electronic and EPR spectra; solid-state temperature-dependent magnetic susceptibility measurements have been performed. Density functional theoretical calculations at the ZORA-B3LYP level have been carried out for all four species in order to obtain a better understanding of the electronic structure of the square planar complexes and the one-electron reduced [Rh^IL₂]³⁻ species. The reactivity of the latter with CH₃I has been studied, and two products have been identified: cis-[Rh^IIII₂(L′′)(L′)] and cis-[Rh^III(CH₃)(I)(L′′)(L′)] where (L′)⁻ represents the S-methylated monoanion of L²⁻ and (L′′)⁰ is the neutral, twice-S-methylated form of (L)²⁻.