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

Neutral hexacoordinate organoantimony compounds LSb(Xyl)C6H4 (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 SbC 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 SbN bond was found to be distinguishable from the stereomutation. Energies of SbN 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. Heteroatom Chem 22:553–561, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/hc.20721