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

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).