title: Synthesis, characterization, and reactivity of furan- and thiophene-functionalized bis(N-heterocyclic carbene) complexes of iron(II).
abstract: The synthesis of iron(II) complexes bearing new heteroatom-functionalized methylene-bridged bis(N-heterocyclic carbene) ligands is reported. All complexes are characterized by single-crystal X-ray diffraction (SC-XRD), nuclear magnetic resonance (NMR) spectroscopy, and elemental analysis. Tetrakis(acetonitrile)-cis-[bis(o-imidazol-2-ylidenefuran)methane]iron(II) hexafluorophosphate (2a) and tetrakis(acetonitrile)-cis-[bis(o-imidazol-2-ylidenethiophene)methane]iron(II) hexafluorophosphate (2b) were obtained by aminolysis of [Fe{N(SiMe3)2}2(THF)] with furan- and thiophene-functionalized bis(imidazolium) salts 1a and 1b in acetonitrile. The SC-XRD structures of 2a and 2b show coordination of the bis(carbene) ligand in a bidentate fashion instead of a possible tetradentate coordination. The four other coordination sites of these distorted octahedral complexes are occupied by acetonitrile ligands. Crystallization of 2a in an acetone solution by the slow diffusion of Et2O led to the formation of cis-diacetonitriledi[bis(o-imidazol-2-ylidenefuran)methane]iron(II) hexafluorophosphate (3a) with two bis(carbene) ligands coordinated in a bidentate manner and two cis-positioned acetonitrile molecules. Compounds 2a and 2b are the first reported iron(II) carbene complexes with four coordination sites occupied by solvent molecules, and it was demonstrated that those solvent ligands can undergo ligand-exchange reactions.
authors.affiliation: Chair of Inorganic Chemistry/Molecular Catalysis, Catalysis Research Center, Technische Universität München , Ernst-Otto-Fischer-Straße 1, D-85747 Garching, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Rieb
authors.forename: Andreas
authors.initials: A
authors.lastname: Raba
authors.forename: Stefan
authors.initials: S
authors.lastname: Haslinger
authors.forename: Manuel
authors.initials: M
authors.lastname: Kaspar
authors.forename: Alexander
authors.initials: A
authors.lastname: Pöthig
authors.forename: Mirza
authors.initials: M
authors.lastname: Cokoja
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Basset
authors.forename: Fritz E
authors.initials: FE
authors.lastname: Kühn