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 [{Pd(C6H4N=NC6H5)(mu-Cl)}(2)] (5) with AgPF6/NH4PF6 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)][PF6] (6A) in high yield, whereas the direct reaction of 5 with two molar equivalents of 9S3 gives [Pd(C6H4N=NC6H5)(9S3)][Pd(C6H4N=NC6H5)Cl-2] (6B) in quantitative yield based on 5. The subsequent reaction of 5 and 6A with the metalloligand [(HMB)Ru-II{eta(3)-tpdt}] [3; HMB = eta(6)-C6Me6, tpdt = S(CH2CH2S-)(2)] results in displacement of the chloride and 9S3 ligands, respectively, to give the Ru-Pd heterobimetallic complex [{(HMB)Ru-II(mu-eta(2):eta(3)-tpdt)}{Pd(C6H4N=NC6H5)}][PF6] (7) in 85% yield. Similar reactions with the Cp* analogue of 3, namely [(Cp*)Ru-III{eta(3)-tpdt}] (4), give the trinuclear complex [{Cp*Ru-III(mu-eta(2):eta(3)-tpdt)}(2)Pd](PF6)(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 center dot H2O and 6B center dot CHCl3) 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 H-1 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. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)