η^2 bonded Nickel(0) thiophene π-complexes - identifying the missing link in catalyst transfer polymerization

We have structurally characterized a nickel(0) thiophene complex that represents a close analog to the proposed intermediates in the mechanism of catalyst transfer polycondensation (CTP) of thiophenes. Additional studies on this intermediate allow us to determine the bonding in such complexes using a combination of nuclear magnetic resonance spectroscopy, X-ray absorption spectroscopy, and DFT-based computations. Our structure of the catalyst agrees with previous postulates but provides important new structural insights into the species. Furthermore, our studies explain why these complexes actually exist and are stable enough to support living CTP.