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A Paramagnetic Heterobimetallic Polymer: Synthesis, Reactivity, and Ring-Opening Polymerization of Tin-Bridged Homo- and Heteroleptic Vanadoarenophanes

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posted on 04.02.2015 by Holger Braunschweig, Alexander Damme, Serhiy Demeshko, Klaus Dück, Thomas Kramer, Ivo Krummenacher, Franc Meyer, Krzysztof Radacki, Sascha Stellwag-Konertz, George R. Whittell
The synthesis of the first tin-bridged bis­(benzene) vanadium and trovacene sandwich compounds and the investigation of their oxidative addition and insertion behavior are reported. The vanadoarenophanes and the corresponding platinum insertion products were fully characterized including electrochemical and electron paramagnetic resonance (EPR) measurements. Controllable ring-opening polymerization of the heteroleptic tin-bridged [1]­trovacenophane using Karstedt’s catalyst yields a high molecular weight polymer (up to Mn = 89 200 g·mol–1) composed of d5-vanadium metal centers in the main chain, making it a rare example of a spin-carrying macromolecule. Magnetic susceptibility measurements (SQUID) confirm the paramagnetic scaffold with repeating S = 1/2 centers in the main chain and suggest antiferromagnetic interactions between adjacent spin sites (Weiss constant Θ = −2.9 K).