Molecular and electronic structures of oxo-bis(benzene-1,2-dithiolato)chromate(V) monoanions. A combined experimental and density functional study

Two oxo-bis(benzene- 1,2-dithiolato)chromate (V) complexes, namely, [CrO(L-Bu)(2)](1-) and [CrO(L-Me)(2)](1-), have been synthesized and studied by UV-vis, EPR, magnetic circular dichroism (MCD), and X-ray absorption spectroscopy and by X-ray crystallography; their electro- and magnetochemistries are reported. H2LBu represents the pro-ligand 3,5-di-tert-butylbenzene-1,2-dithiol, and H2LMe is the corresponding 4-methyl-benzene-1,2-dithiol. A structural feature of interest for both the complexes is the folding of the dithiolate ligands about the S-S vector providing C, symmetry to the complexes. Geometry optimizations using all-electron density functional theory with scalar relativistic corrections at the second-order Douglas-Kroll-Hess (DKH2) and zeroth-order regular approximation (ZORA) levels result in excellent agreement with the experimentally determined structures and electronic and S K-edge X-ray absorption spectra. From DFT calculations, the C-s instead of C-2 nu symmetry for the complexes is attributed to the strong S(3p) -> Cr(3dx(2)-/y(2)) pi-donation in C-s geometry providing additional stability to the complexes.