The thioethers 2-pyridylmethyl p-tolyl sulfide (a) and p-chlorophenyl 2-pyridylmethyl sulfide (b) react with the precursors cis-[RuCl 2 (N,N-diimine) 2 ] [diimine = di-2-pyridyl sulfide (dps), 1; 2,2Ј-bis(4-methylpyridyl) sulfide (4mdps), 2; 2,2Ј-bis(5-methylpyridyl) sulfide (5mdps), 3; di-2-pyrimidyl sulfide (dprs), 4; and 2,2Ј-bis(5-ethylpyrimidyl) sulfide (5edprs), 5] in the presence of NH 4 PF 6 to give the complexes [Ru(N,Ndiimine) respectively. As a consequence of the N,S chelation all the complexes contain a five-membered RuSCCN(Ru−N) ring, the sulfur and ruthenium atoms of which are stereogenic centres, with (R) and (S) and ∆ and Λ configurations, respectively. Furthermore, the coordinated thioethers contain anisochronous methylene protons and phenyl protons which are sensor nuclei for pyramidal sulfur inversion and rotation of the pendant phenyl ring, respectively. In the low-temperature 1 H NMR spectra of the complexes a single AB system for the methylene protons, in agreement with a fast sulfur inversion, is observed. Well-separated signals of the two ortho-as well as the meta-phenyl protons, indicating restricted phenyl rotation, are also observed. At higher temperatures

The thioether ligands L [L = 2-pyridylmethyl 2Ј-pyridyl sulfide (L 1 ), 2-pyridylmethyl 2Ј-pyrimidyl sulfide (L 2 ) and 2-pyr-investigations show that these potentially tridentate ligands act as N,S-bidentate species, to form a five-membered RuSCCN(Ru-N) ring, and in certain cases, as N-monodentate species coordinated to the ruthenium through the 2-pyridylmethyl group. The N,S-chelated species contain chiral sulfur and ruthenium atoms with (R) and (S), and Δ and Λ configurations, respectively. Two invertomers and two sets of NMR signals in the slow-exchange region are expected. However, the low-temperature 1 H NMR spectra show that sulfur inver-