Structure and dynamic behavior of neutral hexacoordinate antimony compounds with intramolecular coordination

Abstract

Neutral hexacoordinate organoantimony compounds LSb(Xyl)C6H 4 (o-Y) [L = tridentate ligand; Xyl = C6H3 (3,5-Me2); Y = CH2 OMe (4), CH2 NMe2 (5), and 2-pyridyl (6)] with intramolecular coordination were synthesized. Single crystal X-ray crystallography revealed that the donor atom (N or O) of 4-6 was coordinated trans to one of the two carbon atoms of the tridentate ligand. Variable temperature (VT) NMR measurements of compounds 4 and 5 indicated that the stereomutations proceeded via dissociation of the Sb-donor (N or O) bond followed by Sb-C bond rotation. Compound 4 was found to have a stereomutation barrier of ca. 12 kcal mol-1. In the case of 5, dissociation of the Sb-N bond was found to be distinguishable from the stereomutation. Energies of Sb-N dissociation 5 and interconversion of enantiomers were estimated to be ca. 15 and ca. 19 kcal mol-1, respectively, from the VT-NMR measurements. © 2011 Wiley Periodicals, Inc.