Bis(1°-amino)cyclodistib(III)azanes: the First Structural Characterization of cis and trans Isomers of a Single Cyclodipnict(III)azane
dataset
posted on 2006-12-25, 00:00 authored by Dana J. Eisler, Tristram ChiversThe dichlorocyclodistib(III)azane [ClSb(μ-N<i><sup>t</sup></i><sup></sup>Bu)]<sub>2</sub> (<b>1</b>) has been shown to exist as the cis isomer in the solid state.
A series of bis(1°-amino)cyclodistib(III)azanes [R‘NHSb(μ-N<i><sup>t</sup></i><sup></sup>Bu)]<sub>2</sub> (<b>2</b>, R‘ = <i><sup>t</sup></i><sup></sup>Bu; <b>3</b>, R‘ = Dipp; <b>4</b>, R‘ = Dmp) has
been prepared by the reaction of <b>1</b> with 2 equiv. of LiNHR‘. On the basis of NMR solution spectra, all three
derivatives are formed as a mixture of cis and trans isomers. In the case of <b>3</b>, the structures of both the cis and
trans isomers have been determined by X-ray crystallography; <i>cis</i>-<b>3 </b>adopts an endo, endo arrangement for the
amido protons of the DippNH groups. Isomerization of <i>trans</i>-<b>3</b> into <i>cis</i>-<b>3</b> occurs slowly in solution. Deprotonation
of <b>2</b> with 2 equiv. of <i><sup>n</sup></i><sup></sup>BuNa or <i>trans</i>-<b>3</b> with <i><sup>n</sup></i><sup></sup>BuLi produces [Na<sub>2</sub>Sb<sub>2</sub>(μ-N<i><sup>t</sup></i><sup></sup>Bu)<sub>4</sub>] (<b>5</b>) and [Li<sub>2</sub>Sb<sub>2</sub>(μ-N<i><sup>t</sup></i><sup></sup>Bu)<sub>2</sub>(μ-NDipp)<sub>2</sub>]
(<b>6</b>), whose solvated cubane structures were established by X-ray crystallography. In contrast, the reaction of <i>cis</i>-<b>3</b>
with 2 equiv. of <i><sup>n</sup></i><sup></sup>BuLi produces the tricyclic compound [Li<sub>2</sub>Sb(μ-N<i><sup>t</sup></i><sup></sup>Bu)<sub>2</sub>(μ-NDipp)(μ-NHDipp)] (<b>7</b>).
