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(LBu)2]1- and [CrO(LMe)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 Cs 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 Cs instead of C2v symmetry for the complexes is attributed to the strong S(3p) → Cr(3dx2-y2) π-donation in Cs geometry providing additional stability to the complexes.