Synthesis and structural characterisation of new RuII[12]aneS4 complexes with polypyridylic and related ligands

Synthesis and structural studies of ruthenium(II) 12S4 complexes with 4,4′-bipyridine: The crystal structures of [Ru(12S4)(bpy)Cl](Cl)·H2O and [{Ru(12S4)Cl}2-μ-(bpy)](PF6)2·2CH3CN

“…We believe the orientation of the lone pair arises from its repulsion by the large, anionic chloride ligand. As noted previously, the sharpness of the lines in 1 H NMR spectra demonstrates that there is no inversion at the S donors, in contrast to previous observations in Ru 12S4 complexes with symmetrical donors, which always show this inversion [5,15]. We would like to highlight that for every Ru 12S4 complex involving Cl À as a ligand, no exchange of the 12S4 ligand via inversion has been ever observed via NMR [19].…”

“…The oxidation in both complexes is assigned as a Ru(II)/Ru(III) couple and contrast the observed irreversible oxidation wave of cis-[Ru(12S4)(dmso)Cl] + (E pa = +598 mV vs. Fc/ Fc + ). However, the replacement of the dmso ligand by a N-donor ligand does appear to result in reversible oxidation behavior since the reported complex cis-[Ru(12S4)(ind)Cl] + (ind = indazole) also demonstrates reversibility in its oxidation wave [15].…”

“…The complex cations [Ru(12S4)(4,4 0 -bpy)Cl] + (1) and [{Ru(12S4)Cl} 2 -l-(4,4 0 -bpy)] 2+ (2) are both prepared from the starting complex cis-[Ru(12S4)(dmso)Cl] + by facile loss of dmso as illustrated in Scheme 1 [15]. A reaction with 1:1 stoichiometry between cis-[Ru(12S4)(dmso)Cl] + and 4,4 0 -bpy produces (1) which is isolated as the chloride salt in a 62% yield.…”

“…The bridging of the 4,4 0 -bpy ligand to both Ru(II) centers in (2) is indicated by the presence of two resonances in its 1 H NMR spectrum and three in the 13 C NMR spectrum. Furthermore, the sharp NMR resonances for the 12S4 region in both (1) and (2) imply that no chemical exchange of the thiacrown is taking place on the NMR time scale [5,15]. In the electronic spectra of the two complexes, one low energy transition near 400 nm is assigned as a MLCT band while the higher energy band near 240 nm is assigned as a pp* transition, similar to observations with other Ru(II) tetrathiacrown complexes with diimine donors [4].…”

“…In contrast, for every case in which the cis ligand environment (relative to the 12S4) is different, such as the two described in this report, one sulfur lone pair points towards the ligands, but the other lone pair points away from the ligands. There are six Ru 12S4 complexes that exhibit this type of behavior in their solid state structures [15,18]. Furthermore, in all of these cases where a chloride ligand is present, the lone pair on the equatorial S donor cis to the chloride always points away from that chloride donor.…”