Ruthenium‐Carbon(Aryl) Bond Cleavage and Change in the Ligand Coordination Mode in a Four‐Membered Ortho‐Metalated Ruthenium(II) Organometallics Promoted by Thiolato Ligands

Abstract

The reaction of Ru(η2‐RL)(PPh3)2(CO)Cl [η2‐RL is C6H2O‐2‐CHNHC6H4R(p)‐3‐Me‐5 and R=Me, OMe, Cl] with excess sodium p‐chlorothiophenolate (p‐ClC6H4SNa) in dichloromethane–tetrahydrofuran medium afforded the binuclear complexes of the type [Ru(PPh3)(η2‐RL)(CO)(p‐ClC6H4S)]2 [η2‐RL is C6H3O‐2‐CHNC6H4R(p)‐3‐Me‐5] in excellent yield. The binding of the thiolato ligands is attended with the cleavage of the Ru–C(aryl) and Ru–Cl bonds in Ru(η2‐RL)(PPh3)2(CO)Cl and the RL ligands are now coordinated with the metals in [Ru(PPh3)(η2‐RL)(CO)(p‐ClC6H4S)]2 via the imine nitrogen and the phenolato oxygen atoms. The CO ligand in [Ru(PPh3)(η2‐RL)(CO)(p‐ClC6H4S)]2 remains trans to the phenolato function as in Ru(η2‐RL)(PPh3)2(CO)Cl. The spectral (UV‐vis, IR, NMR, mass) and electrochemical data of the complexes are included. In dichloromethane solution the complexes display two successive one‐electron oxidation waves. The comproportionation constants (KC) as calculated by the ▵E1/2 values of the complexes are in the order of 105 indicating that the two metal centers in [Ru(PPh3)(η2‐RL)(CO)(p‐ClC6H4S)]2 are only weakly coupled by the bridging thiolato liagnds. Structure determinations of [Ru(PPh3)(η2‐RL)(CO)(p‐ClC6H4S)]2 (R=Me, OMe) have revealed a distorted octahedral RuCONPS2 coordination sphere with the pairs (P, S), (C, O), and (N, S) defining the three trans directions. The Ru⋅⋅⋅⋅Ru distances in the complexes are clearly outside of the range for a Ru‐Ru single bond. The electronic structures and the absorption spectra of the complexes are also scrutinized by the density functional theory (DFT) and Time‐dependent DFT analysis.