Synthesis, structure and spectral properties of dithiocarbamato bridged dirhenium(III,II) complexes: a combined experimental and theoretical study

Sodium salts of dimethyldithiocarbamate, diethyldithiocarbamate and pyrrolidinedithiocarbamate react with the multiply bonded paramagnetic dirhenium(III,II) complex Re2(μ-O2CCH3)Cl4(μ-dppm)2, 1 (dppm = Ph2PCH2PPh2) in refluxing ethanol to afford the paramagnetic substitution products of the type Re2(η2-S,S)2(μ-S,S)(μ-Cl)2(μ-dppm), where S,S represents the dithiocarbamato ligands [S,S = S2CNMe2, 4(LMe); S2CNEt2, 4(LEt) and S2CN(CH2)4, 4(LPyr)]. These are the first examples of dirhenium complexes that contain bridging dithiocarbamato ligand along with the dppm ligand. These complexes have very similar spectral (UV-Vis, IR, EPR) and electrochemical properties which are also reported. The identity of 4(LEt) has been established by single-crystal X-ray structure determination (Re-Re distance 2.6385 (9) Å) and is shown to have edge-shared bioctahedral structure. The electronic structure and the absorption spectra of the complexes are scrutinized by the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) analyses.