title: Organometallic Fe-Fe Interactions: Beyond Common Metal-Metal Bonds and Inverse Mixed-Valent Charge Transfer.
abstract: The compounds [Fe(CO)3(dRpf)]n+, n=0, 1, 2 and dRpf=1,1'-bis(dicyclohexylphosphino)ferrocene ([1]n+) or 1,1'-bis(diisopropylphosphino)ferrocene ([2]n+), were obtained as two-step reversible redox systems by photolytic and redox reactions. The iron-iron distance decreases from about 4 Å to about 3 Å on oxidation, which takes place primarily at the tricarbonyliron moiety. Whereas ferrocene oxidation is calculated to occur only in excited states, the near infrared absorptions of the mixed-valent monocations are due to an unprecedented "inverse" inter-valence charge transfer from the electron-rich iron(II) in the ferrocene backbone to the electron-deficient tricarbonyliron(I). Protonation of complex 1 results in the formation of the structurally characterized hydride [1H]BF4, which reacts with acetone to form the dication, 12+, and isopropanol. While the hydride [2H]BF4was found to be unstable, protonation of 2 in acetone resulted in the clean formation of 22+,formally a hydrogen transfer.
authors.affiliation: Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70550, Stuttgart, Germany.
authors.forename: Mark R
authors.identifier: http://orcid.org/0000-0001-7585-5757
authors.initials: MR
authors.lastname: Ringenberg
authors.affiliation: Institut für Theoretische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70550, Stuttgart, Germany.
authors.forename: Max
authors.initials: M
authors.lastname: Schwilk
authors.affiliation: Lehrstuhl für Anorganische Chemie I, Ruhr-Universität Bochum, Universitätsstraße 150, 44801, Bochum, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Wittkamp
authors.affiliation: Lehrstuhl für Anorganische Chemie I, Ruhr-Universität Bochum, Universitätsstraße 150, 44801, Bochum, Germany.
authors.forename: Ulf-Peter
authors.identifier: http://orcid.org/0000-0002-1577-2420
authors.initials: UP
authors.lastname: Apfel
authors.affiliation: Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70550, Stuttgart, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Kaim
keywords: carbonyl complexes; ferrocene; metal-metal interactions; mixed valence; organoiron compounds