title: Subtle effects control the polymerisation mechanism in α-diimine iron catalysts.
abstract: α-diimine iron complexes have been suggested to catalyse polymerisation via two distinct pathways, depending on the spin state of the iron complex. Here, we study a typical complex of this family, (R'')[N,N]FeCl(2), with [N,N] = Cy-N=CR''-CR''=N-Cy (Cy = cyclohexyl, R'' = PhF (para-fluorophenyl), PhOMe (para-methoxyphenyl), PhNMe(2) (para-dimethylaminophenyl). With R'' = PhF, PhOMe, polymerisation proceeds as a catalytic chain transfer (CCT) mechanism, with R'' = PhNMe(2), the polymerisation follows an atom transfer radical polymerisation (ATRP) pathway. Contrary to previous suggestions, we show that the spin-states of the complexes involved are not affected by the R'' group. Instead, the different behaviour arises from a subtle interplay between the electron-withdrawing or donating character of the reasonably distant phenyl substituent and the iron centre, and small but crucial differences in the reorganisation energies affected during the reactions.
authors.affiliation: Institut de Química Computacional and Departament de Química, Universitat de Girona, Campus Montilivi, ES-17071, Girona, Spain.
authors.forename: Mikael P
authors.initials: MP
authors.lastname: Johansson
authors.forename: Marcel
authors.initials: M
authors.lastname: Swart
mesh_terms: D001593:Benzyl Compounds / Q000737:chemistry; D002384:Catalysis; D004583:Electrons; D007097:Imines / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000737:chemistry*; D058105:Polymerization
chemical_list: D001593:Benzyl Compounds; D007097:Imines; D009942:Organometallic Compounds; C021292:benzyl chloride; D007501:Iron