Modeling and experiment reveal an unexpected stereoelectronic effect on conformation and scalar couplings of alpha-aminoorganostannanes, with possible relevance to the tin-lithium exchange reaction.
The solution conformation of N-methyl-2-(tributylstannyl)piperidines has been determined through the use of vicinal 119Sn-13C coupling constants, revealing a conformational distortion caused by an unexpected stereoelectronic effect in some cases. Specifically, the "equatorial" conformer is distorted into a half-chair, in which the nitrogen lone pair eclipses the C-Sn bond. This distortion, which "costs" approximately 1 kcal/mol, correlates with a conformational dependence of geminal 119Sn-15N couplings and a possible correlation with reactivity in the tin-lithium exchange reaction.
Santiago
Marcelina
M
Department of Chemistry, University of Miami, Coral Gables, Florida 33124, USA.
Low
Eddy
E
Chambournier
Gilles
G
Gawley
Robert E
RE
D002247:Carbon Isotopes; D008094:Lithium / Q000737:chemistry*; D008956:Models, Chemical; D008968:Molecular Conformation; D009584:Nitrogen / Q000737:chemistry; D009587:Nitrogen Isotopes; D009947:Organotin Compounds / Q000737:chemistry*; D010880:Piperidines / Q000737:chemistry; D014001:Tin / Q000737:chemistry*; D014220:Trialkyltin Compounds / Q000737:chemistry
D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D009947:Organotin Compounds; D010880:Piperidines; D014220:Trialkyltin Compounds; C011559:tributyltin; D014001:Tin; D008094:Lithium; D009584:Nitrogen