The synthesis and the structural characterization of azahelicene platinum complexes obtained from cis-PtCl2(NCEt)(PPh3) and from ligands that differ both in terms of the position of the N atom and the number of fused rings, is reported. These square planar complexes of 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 a chirality control of the cis-trans stereochemistry. Indeed, while starting from a racemic mixture of aza[6]helicene, Pt complexes with a cis configuration are invariably obtained, the more thermodynamically stable trans isomers are formed when using enantiopure ligands. We further corroborated these results by NMR analysis in solution.

Synthesis and Structural Properties of Aza[n]helicene Platinum Complexes: Control of Cis and Trans Stereochemistry

MENDOLA, DANIELE;CASTIGLIONE, FRANCA;Martí Rujas, Javier;MALPEZZI, LUCIANA;MELE, ANDREA;
2016-01-01

Abstract

The synthesis and the structural characterization of azahelicene platinum complexes obtained from cis-PtCl2(NCEt)(PPh3) and from ligands that differ both in terms of the position of the N atom and the number of fused rings, is reported. These square planar complexes of 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 a chirality control of the cis-trans stereochemistry. Indeed, while starting from a racemic mixture of aza[6]helicene, Pt complexes with a cis configuration are invariably obtained, the more thermodynamically stable trans isomers are formed when using enantiopure ligands. We further corroborated these results by NMR analysis in solution.
2016
Helicenes, Platinum, Cis/Trans isomerism, Chirality
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11311/995761
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