The complex [Ru(py)(3)([9]aneS(3))][PF6](2), 1 (py = pyridine), has proved to be a suitable starting material for the synthesis of heteroleptic Ru(ZI) complexes. By exploiting unfavorable steric interactions between 2-H and 6-H hydrogens of coordinated pyridyl ligands, we have synthesized half-sandwich complexes incorporating the thiocrown [9]aneS(3) and a variety of facially coordinated N-donor ligands. Such complexes are easily prepared: Stirring 1 at room temperature in the presence of a suitable nitrile ligand leads to the exclusive substitution of one py ligand to produce complexes such as [([9]aneS(3))Ru(py)(2)(NCMe)] [PF6](2), 2. However, if the same reaction is carried out at higher temperatures, two py ligands are substituted, leading to complexes such as [([9]aneS(3))Ru(py)(NCMe)(2)][PF6](2), 3. An alternative approach to such heteroleptic species has also been developed which exploits the restricted ability of thioethers to neutralize positive charges through a-donation. This phenomenon allows the synthesis of heteroleptic complexes in a two-step procedure via monocationic species. By variation of the donor/acceptor properties of ligands incorporated into the [Ru([9]aneS(3))](2+) metal center, it is possible to tune the Ru(III)/Ru(II) redox couple over a range of >700 mV. The solid-state structures of 1-3 were confirmed by X-ray crystallography studies. Crystal data: C22H30F12N4O2P2RuS3 (1.CH3NO2), monoclinic, Cc, a = 23.267(5) Angstrom, b = 11.5457(18) Angstrom, c = 26.192(5) Angstrom, alpha = 90 degrees, beta = 114.836(10)degrees, gamma = 90 degrees, Z = 8; C18H25F12N3P2RuS3 (2), triclinic, P1, a = 11.3958(19) Angstrom, b = 11.4280(19) Angstrom, c = 11.930(2) Angstrom, alpha = 100.518(3)degrees, beta = 100.542(3)degrees, gamma = 112,493(3)degrees, Z = 2; C15H23F12N3P2RuS3 (3), orthorhombic, Pna2(1), a = 14.748(5) Angstrom, b = 18.037(18) Angstrom, c = 10.341(5) Angstrom, alpha = 90 degrees, beta = 90 degrees, gamma = 90 degrees, Z = 4.