A Flexible Approach to Strained Sandwich Compounds: Chiral [1]Ferrocenophanes with Boron, Gallium, Silicon, and Tin in Bridging Positions. Issue 40 (14th August 2013)

• Record Type: Journal Article
• Authors: Sadeh, Saeid; Schatte, Gabriele; Müller, Jens
• Is Part Of: Chemistry. Volume 19:Issue 40(2013)
• Page Start: 13408
• Page End: 13417
• Publication Date: 2013-08-14
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201301991
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>The enantiomerically pure dibromoferrocene <bold>3</bold> [(<italic>S<sub>p</sub></italic>, <italic>S<sub>p</sub></italic>)‐1, 1′‐dibromo‐2, 2′‐di(isopropyl)ferrocene], equipped with two <italic>i</italic>Pr groups in α positions, was prepared using known "Ugi amine" chemistry. Species <bold>3</bold> was targeted in order to gain access to new [1]ferrocenophanes ([1]FCPs) to be used as monomers for ring‐opening polymerization. The <italic>i</italic>Pr groups on the sandwich unit were introduced to stabilize bridging moieties, as well as to increase solubilities of targeted metallopolymers. The planar chiral dibromide <bold>3</bold> can quantitatively be lithiated at 0 °C [2 equiv <italic>n</italic>BuLi, hexanes/thf (9:1), 30 min]. Salt‐metathesis reactions with respective element dichloride species gave chiral [1]FCPs with a variety of bridging moieties [ER<sub><italic>x</italic></sub>=Ga[2‐(Me<sub>2</sub>NCH<sub>2</sub>)C<sub>6</sub>H<sub>4</sub>] (<bold>4 a</bold>), SiMe<sub>2</sub> (<bold>4 b</bold>), Sn<italic>t</italic>Bu<sub>2</sub> (<bold>4 c</bold>), BN<italic>i</italic>Pr<sub>2</sub> (<bold>4 d</bold>)]. The new [1]FCPs were fully characterized including single‐crystal X‐ray analysis. The stabilizing <italic>i</italic>Pr groups on the Cp rings increase the thermal stabilities of <bold>4 b</bold>–<bold>d</bold> compared to known [1]FCPs, equipped with the same bridging moieties. All three compounds <bold>4 b</bold>–<bold>d</bold> are volatile and could be isolated by vacuum sublimation. Our new approach to [1]FCPs has the potential to overcome many of the existing difficulties in ferrocenophane chemistry, such as limited stability of starting monomers and low solubilities of resulting polyferrocenes.</p> </abstract>