A Cyclometallated (Azobenzene)palladium(II) complex of 1,4,7- trithiacyclononane: Synthesis and reactivity with thioether-dithiolate metalloligands, single-crystal X-ray diffraction analyses and electrochemical studies

The treatment of [jPd(C₆H₄N=NC₆H ₅)(μ-Cl)j₂](5) with AgPF₆/NH ₄PF₆ in acetone, followed by the addition of two molar equivalents of 1,4,7-trithiacyclononane (9S3), gives the deep red complex [Pd(C₆H₄N=NC₆H₅)(9S3)][PF ₆](6A)in high yield, whereas the direct reaction of 5 with two molar equivalents of 9S3 gives [Pd(C₆H₄N=NC₆H ₅)(9S3)][Pd- (C₆H₄N=NC₆H ₅)Cl₂](6B) in quantitative yield based on 5. The subsequent reaction of 5 and 6A with the metalloligand [(HMB)Ru ⁿ{r³-tpdt}] [3; HMB = n⁶-C₆Me ₆, tpdt = S(CH₂- CH₂S^-)₂] results in displacement of the chloride and 9S3 ligands, respectively, to give the Ru-Pd heterobimetallic complex [{(HMB)Ru^II(̂-n ₂:n₃-tpdt)jjPd(C₆H₄nf>N= NC<₆H₅)j][PF₆](7) in 85% yield. Similar reactions with the Cp analogue of 3, namely [(Cp*)Ru^m{r| ³-tpdt}] (4), give the trinuclear complex. [jCp*Ru ^III(μ-n²:n³-tpdt)j₂Pd](PF ₆)₂ (8), in which all the ligands on palladium have been displaced, in a yield of around 80%. X-ray diffraction analyses of 6A, 6B and its solvates (6B-H₂O and 6B-CHCl?₃) have shown that short atom-atom interactions between the cation and the counterion and lattice solvent molecules have a significant effect on the bond parameters of the molecules, and ¹H NMR spectroscopy indicates that these interactions persist even in solution. The single-crystal X-ray structure of 7 has also been determined. Cyclic voltammetry experiments have been performed on 6A, 6B and 7 in CH₂Cl₂ and CH₃CN at GC and Pt electrodes.