Synthesis and Structural Properties of Aza[n]helicene Platinum Complexes: Control of Cis and Trans Stereochemistry
Daniele Mendola, Nidal Saleh, Nora Hellou, Nicolas Vanthuyne, Christian Roussel, Loïc Toupet, Franca Castiglione, Federica Melone, Tullio Caronna, Francesca Fontana, Javier Martı́-Rujas, Emilio Parisini, Luciana Malpezzi, Andrea Mele, Jeanne Crassous
The synthesis and structural characterization of azahelicene platinum complexes obtained fromcis-PtCl2(NCEt)(PPh3) and from ligands that differ in terms of both the position of the nitrogen atom and the number of fused rings are reported. These square-planar complexes of the general formula PtCl2(nHm)(PPh3) (n = 4, 5; m = 5, 6) display mainly a cis configuration. However, by X-ray crystallographic analysis, we show that for both PtCl2(4H6)(PPh3) and PtCl2(5H6)(PPh3) there is chirality control of the cis/trans stereochemistry. Indeed, starting from a racemic mixture of azahelicene, platinum complexes with a cis configuration are invariably obtained, and the more thermodynamically stable trans isomers are formed when using enantiopure ligands. We further corroborated these results by NMR analysis in solution.
Circular dichroism, Stereochemistry, Coordination chemistry, Inorganic chemistry