The new pyridinediphosphinite ligand PONOP (1) was synthesized in one step from 2,6-pyridinedimethanol and diphenylchlorophosphane. Reaction of 1 with PtCl(2)(PhCN)(2) led to the neutral homobimetallic complex [Pt(2)Cl(4)(PONOP)(2)] (2), where the benzonitriles have been substituted by the phosphorus atoms of 1. The X-ray structure of 2 revealed a metallamacrocycle where the pyridines remained free. Addition of 2 equiv of [Cu(MeCN)(4)](BF(4)) to 2 led to CuCl and to the binuclear dicationic complex [Pt(2)Cl(2)(PONOP)(2)](BF(4))(2) (3), where chloro ligands have been substituted by pyridine groups. Conversely, reaction of 3 with chloride anions gave back complex 2. Solid-state (X-ray) and solution (NMR) studies indicated that after the transformation of 2 into 3, the platinum centers were brought much closer and the pyridinediphosphinite ligand was stiffened. The methylene NMR protons of 3 were strongly deshielded, and the corresponding proton-phosphorus coupling constants followed a Karplus-type relationship.

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The chiral diphospholane ligands Duphos (1) and Duxantphos (2), which can be differentiated by their bite angle, were applied to palladium-catalysed asymmetric reactions, essentially allylic alkylations with symmetrically (3a−d) or unsymmetrically (5a,b) substituted allylic acetates as substrates. The most interesting results were found with the first series of substrates in which 2 was more reactive and/or selective than 1. The model complexes of the catalytic intermediates [Pd{(S,S)-1}(η 3 -cyclohexenyl)](BF 4 ) (10) and exo-[Pd{(R,R)-2}(η 3 -cyclohexenyl)](SbF 6 ) (11) could be characterised by X-ray crystallography.