Ru(II) thioether complexes with dangling pyridine ligands

Through two different methods, new Ru(II) polypyridyl complexes were prepared in an attempt to replicate previously reported heptacoordinate Ru(II) syntheses. The tetradentate thioethers, 1,8-bis(2′-pyridyl)-3,7-dithianonane (Pdto), 1,9-bis(2′-pyridyl)-3,7-dithianonane (Pdtn), and 1,10-bis(2′-pyridyl)-3,8-dithiadecane (Pdtd), were used to form dinuclear ruthenium(II) complexes of the type [{Ru(L1)}2(μ-Cl)2]2+via reaction with RuCl3·xH2O. Upon reaction of the dinuclear complexes with the triimine ligand 2,6-bis(N′-methyl-benzimidazolyl)pyridine (Me2Bzimpy), facile symmetrical bridge cleavage occurs, producing mononuclear complexes of the form [Ru(L1)(L2)]2+, where L1 is one of the three tetradentate thioether ligands and L2 is the tridentate triimine. A second method of producing the mononuclear [Ru(L1)(L2)]2+ complexes involves the reaction of Ru(L2)Cl3 with L1 under ethanolic conditions. In such mononuclear complexes, one of the pyridine arms of the tetradentate thioether is forced to be uncoordinated, due to the firmly hexacoordinate nature of Ru(II). A similar experiment was conducted using the pentadentate thioether 1,11-bis(2′-pyridyl)-3,6-9-dithianonane (Pttu) and the diimine Phen, forming the stable hexacoordinate [Ru(Pttu)(Phen)]2+ complex. The mononuclear complexes exhibit single-electron Ru(II) → Ru(III) oxidative response, in the range of +825 to +845 mV versus APE, involving the removal from an electron from the t2g orbital set.

Graphical abstractDue to the firmly hexacoordinate nature of Ru(II), it transpires that in the mononuclear [Ru(Pttu)(Phen)]2+ complex, one of the pyridine arms of the tetradentate thioether is forced to be uncoordinated.Figure optionsDownload full-size imageDownload as PowerPoint slide