A Dinuclear Double-Stranded Oxido Complex of Re-V with a Bis(benzene-o-dithiolato) Ligand

The reaction of [ReOCl3(PPh3)2] with l,2-bis(2,3-dimercaptobenzamido)ethane (H4-1) in the presence of Na2CO3 in methanol, under anaerobic conditions affords the dinuclear Rev oxido complex [PPhI4]2[ReO(1)] 2 containing two distorted square-pyramidal {RevOS 4} units bridged by the ligand strands in a double-stranded fashion. The coordination geometry around the metal centers is similar to the one observed, for [ReO(bdt)2]-. The ReS4 planes are arranged in a coplanar fashion and are not twisted around the metal-metal vector, which prevents the complex to adopt a helical structure. Luminescence studies show the presence of emission bands, which are assigned to singlet-singlet transitions exhibiting very fast decays (ca. 10 ns), Theoretical Density Functional (DFT) studies on geometry and electronic properties were performed employing the hybrid B3LYP and PBE1PBE functionals. While the general trends observed in the experi-mental data are well reproduced in all cases, a good agreement was obtained using PBE1PBE, in particular for the ReS bonds. Natural Bond. Orbitals (NBO) analysis indicates the presence of polarized Re=O and Re-S bonds, both of them polarized toward the non-metal. The calculation show that the molecular orbitais of the Rev are doubly degenerated, the occupied 5d orbital of rhenium lying beneath occupied sulfur-based MOs due to the rigid geometry imposed by the CC backbone of the bis(benzene-o-dithiolato) ligands. The origin of all absorption bands is ascribed to a ligand-to-metal charge transfer (LMCT), in which occupied, sulfur-based orbitals and unoccupied rhenium-centered orbitals are involved.