Spectroscopic, structural and computational studies of thiophenolato bridged dirhenium(III,III) complexes

Abstract

Thiophenol (HL_H), 4-methylthiophenol (HL_Me) and 4-chlorothiophenol (HL_Cl) react with dirhenium(III,II) complex [Re₂(µ-O₂CCH₃)Cl₄(µ-dppm)₂] (1) (dppm = Ph₂PCH₂PPh₂) in refluxing dry toluene to afford the diamagnetic Re₂⁶⁺ complexes of the type [Re₂(μ-L_R)₂Cl₄(μ-dppm)₂] (2(L_R)) [L_R = C₆H₅S^–, p-MeC₆H₄S^– and p-ClC₆H₄S^–]. These are the first examples of thiophenolato bridged dirhenium complexes with a Re₂⁶⁺ core containing dppm ligand. The spectral properties of the complexes are reported. In the electrochemical experiment, the type 2(L_R) complexes show one quasi-reversible one-electron oxidation and one-electron reduction waves. The identity of 2(L_Me) has been established by single-crystal X-ray structure determination (Re–Re distance = 2.6178(5) Å) and is shown to have an edge-shared bi-octahedral structure. DFT analysis shows that the highest occupied molecular orbitals are mainly composed of metal δ-based orbitals whereas the lowest unoccupied molecular orbitals are metal π*-based orbitals and the electronic ground state for the 2(L_R) complexes is σ²π²δ*²δ². Time-dependent DFT (TD-DFT) analysis shows that the sharp peak at 455 nm in the experimental UV-vis spectrum is mainly due to the [Cl(π)]→[Re₂(π*)] transition.

Graphical Abstract

Keywords:

• Dirhenium
• thiophenolato
• edge-shared bi-octahedra
• density functional theory
• electrochemical study

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Financial support from the Department of Science and Technology, Government of India (No. SR/S1/IC-65/2010) and the Council of Scientific & Industrial Research, New Delhi, India (No. 01(2898)/17/EMR-II) are gratefully acknowledged, University of Kalyani for infrastructural facilities. The support of DST-FIST to the Department of Chemistry and DST-PURSE to the University of Kalyani are acknowledged. J. Chowdhury thanks CSIR, India for the pre-doctoral fellowships.