Reaction of the dirhenium(III,II) complex Re2(μ-O2CCH3)Cl4(μ-dppm)2 with dithioterephthalic acids: A combined experimental and theoretical study

The reaction between the multiply-bonded dirhenium(III,II) complex [Re2(mu-O2CCH3)Cl4(mu-dppm)2] (dppm = Ph2PCH2PPh2) and dithioterephthalic acid or 2,5-dimethyldithioterephthalic acid in refluxing ethanol affords the paramagnetic Re?+ complexes [Re2(mu-Cl)2(mu-dppm)2(12-OSCC6H2R2CO2CH2CH3)2]Cl (R = H, 2; R = Me, 3). In the course of the reaction, one of the thio-acid (COS) coordination sites of the ligand chelated with dirhenium unit whereas another site esterifies with the ethanol solvent. These are the first example of Re2 complexes containing thio-terephthalate ligands. The spectroscopic (UV-vis-NIR, EPR) and electrochemical (CV, DPV) properties of the complexes are reported. The edge-sharing bioctahedral (ESBO) structure of complex 2 has been established by single-crystal X-ray diffraction study. The Re-Re bond length 2.6504(4) angstrom is compatible with the electronic configuration sigma 2 pi 2 delta*2 delta 2 pi*1 obtained from the density functional theory (DFT) calculation. Time dependent DFT (TDDFT) calculation has been included to rationalize the absorption spectra of the complexes.