Article ID Journal Published Year Pages File Type
1340443 Polyhedron 2006 17 Pages PDF
Abstract

We have synthesized and fully characterized three chiral ligands with a rigid xanthene backbone having phosphorus and/or nitrogen donor atoms, viz. the diimine 5 and the iminophosphines 15a and 15b. When the imine functions were derived from (1R)-camphor (compounds 5 and15a), their configuration was (E), whereas a dynamic mixture of (Z) and (E) isomers was observed in solution for the (1S)-fenchone derivative 15b. Attempts to coordinate palladium (II) with these ligands have led to untractable mixtures. By contrast, we isolated in good yields the well-defined silver (I) complexes 18–20, in which the ligands were bidentate, and the rhodium (III) complex 21 in which ligand 15a was tridentate. Complexes 18, 19 and 21 were characterized by X-ray crystallography. A fluxionality of the silver complexes owed to conformational (flip-flop) equilibrium was revealed by VT-NMR analysis. The rhodium complex was not fluxional. In the silver complexes, the camphimine was in the (E) configuration as in the free ligand, whereas it had isomerized to (Z) in the rhodium complex. Pd-, Ag- or Rh-catalyzed reactions implemented with our ligands have in general led to good conversions but modest enantioselectivities (0–36%).

Graphical abstractChiral ligands with a rigid xanthene backbone and phosphorus and/or nitrogen donor atoms were synthesized and characterized. They behaved as bidentate ligands in silver (I) complexes, whereas a tridentate coordination mode was observed in a rhodium (III) complex.Figure optionsDownload full-size imageDownload as PowerPoint slide

Related Topics
Physical Sciences and Engineering Chemistry Inorganic Chemistry
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