American Chemical Society
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Deltoid versus Rhomboid: Controlling the Shape of Bis-ferrocene Macrocycles by the Bulkiness of the Substituents

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posted on 2017-02-06, 18:19 authored by Viktor Hoffmann, Loïc le Pleux, Daniel Häussinger, Oliver T. Unke, Alessandro Prescimone, Marcel Mayor
Precise structural control of heteroannularly disubstituted ferrocene (Fc) structures is very challenging as the high rotational mobility of the Fc unit allows a large conformational diversity. Herein we present the syntheses, characterization, and electrochemical investigation of two complementary bis-ferrocene macrocycles, built up via Sonogashira cross coupling and intramolecular ring-closing reaction. While the X-ray structure of 1,2-ethynylbenzene bridged bis-ferrocene complex 1 shows a deltoidal conformation, a stretched oriented rhomboidal bis-ferrocene metallacycle 2 is formed when the peripheral benzene rings are decorated with bulky tert-butylsulfanyl groups. VT-NMR spectroscopy is used to assign the rotation of the embedded Fc units in rhomboid 2. Moreover, cyclic voltammetry (CV) of deltoid 1 and rhomboid 2 indicate that electronic communication between both ferrocenyl groups can be neglected, while the electrostatic through space coupling is significant.