A Flexible and Modular Approach to [2]Ferrocenophanes with Nitrogen in Bridging Position

Details zur Publikation
Dey, S.
University of Saskatchewan
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Zusammenfassung, Abstract

[n]Ferrocenophanes are interesting because these strained sandwich compounds can be polymerized to metallopolymers by ring-opening polymerization reactions. Although there are many strained [n]ferrocenophanes known, only few of them can be polymerized with controlled molecular weight and molecular weight distribution. Among them, the Me2Si-bridged [1]ferrocenophane is the mostly explored species. To expand the possibility of accessible monomers we synthesized a new class of strained [2]ferrocenophanes. Although there are plenty of examples of symmetrically bridged [2]ferrocenophanes known, similar species with two different bridging elements are comparatively rare. In order to induce a difference in polarity over the diatomic bridge, nitrogen was introduced in the bridging position. Via a known synthetic methodology, one bromine of 1,1'-dibromoferrocene was selectively replaced by an amino group.

The resulting compound was then modified into a class of easily synthesizable starting materials which were cleanly lithiated under optimized condition and in-situ reacted with different elemental dihalides to produce unsymmetrically bridged aza[2]ferrocenophanes. This is the first reported development of a modular synthetic approach towards this class of strained sandwich compounds. Aza[2]ferrocenophanes with boron, gallium, silicon, tin, and phosphorus as the second bridging element were prepared and characterized. Among these strained compounds, only the silicon- and tin-bridged species have been investigated for ring-opening polymerizations. However, no polymeric materials were obtained from these reactions. The preparation of azaphospha[2]ferrocenophanes was surprisingly difficult and led to unexpected products like 1,1'-disubstituted ferrocenes and azacarbaphospha [3] ferrocenophane.

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Zuletzt aktualisiert 2021-07-10 um 10:02