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Publisher: Weinheim : Wiley-VCH × Subject: iron ×

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    Covalency-Driven Preservation of Local Charge Densities in a Metal-to-Ligand Charge-Transfer Excited Iron Photosensitizer
    (Weinheim : Wiley-VCH, 2019) Jay, Raphael M.; Eckert, Sebastian; Vaz da Cruz, Vinicius; Fondell, Mattis; Mitzner, Rolf; Föhlisch, Alexander
    Covalency is found to even out charge separation after photo-oxidation of the metal center in the metal-to-ligand charge-transfer state of an iron photosensitizer. The σ-donation ability of the ligands compensates for the loss of iron 3d electronic charge, thereby upholding the initial metal charge density and preserving the local noble-gas configuration. These findings are enabled through element-specific and orbital-selective time-resolved X-ray absorption spectroscopy at the iron L-edge. Thus, valence orbital populations around the central metal are directly accessible. In conjunction with density functional theory we conclude that the picture of a localized charge-separation is inadequate. However, the unpaired spin density provides a suitable representation of the electron–hole pair associated with the electron-transfer process. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
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    Dehydropolymerisation of Methylamine Borane and an N-Substituted Primary Amine Borane Using a PNP Fe Catalyst
    (Weinheim : Wiley-VCH, 2020) Anke, Felix; Boye, Susanne; Spannenberg, Anke; Lederer, Albena; Heller, Detlef; Beweries, Torsten
    Dehydropolymerisation of methylamine borane (H3B⋅NMeH2) using the well-known iron amido complex [(PNP)Fe(H)(CO)] (PNP=N(CH2CH2PiPr2)2) (1) gives poly(aminoborane)s by a chain-growth mechanism. In toluene, rapid dehydrogenation of H3B⋅NMeH2 following first-order behaviour as a limiting case of a more general underlying Michaelis–Menten kinetics is observed, forming aminoborane H2B=NMeH, which selectively couples to give high-molecular-weight poly(aminoborane)s (H2BNMeH)n and only traces of borazine (HBNMe)3 by depolymerisation after full conversion. Based on a series of comparative experiments using structurally related Fe catalysts and dimethylamine borane (H3B⋅NMe2H) polymer formation is proposed to occur by nucleophilic chain growth as reported earlier computationally and experimentally. A silyl functionalised primary borane H3B⋅N(CH2SiMe3)H2 was studied in homo- and co-dehydropolymerisation reactions to give the first examples for Si containing poly(aminoborane)s. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.