The presence of a stereogenic carbon centre (R or S) in the racemic ligand 1-(diphenylphosphanyl)propane-2-thiol induces a conformational preference (λ or δ) in the five-membered chelate ring of its 2:1 and 2:2 coordination compounds with NiII: the mononuclear trans-[Ni{SCH(CH3)CH2PPh2-P,S}2] (1) and the binuclear trans-[Ni{μ-SCH(CH3)CH2PPh2-P,S}(Cl)]2 (2). Both complexes exist as mixtures of two diastereomers: racemic-trans (Rλ, Rλ and Sδ, Sδ) and meso-trans (Rλ, Sδ), in an equilibrium displaced towards the more stable isomer, the meso-trans for 1 (calculated ΔE = < −0.1 kcal·mol−1) and the racemic-trans for 2 (calculated ΔE = −5.1 kcal·mol−1). This phenomenon is especially evident for complex 2, in which an efficient chiral recognition between the two enantiomeric forms of the racemic ligand was observed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)