title: A Redox-Switchable Germylene and its Ligating Properties in Selected Transition Metal Complexes.
abstract: The synthesis, structure, and full characterization of a redox-switchable germylene based on a [3]ferrocenophane ligand arrangement, [Fc(NMes)2Ge] (4), is presented. The mesityl (Mes)-substituted title compound is readily available from Fc(NHMes)2(2) and Ge{N(SiMe3)2}2, or from the dilithiated, highly air- and moisture-sensitive compound Fc(NLiMes)2⋅3 Et2O (3) and GeCl2. Cyclic voltammetry studies are provided for 4, confirming the above-mentioned view of a redox-switchable germylene metalloligand. Although several 1:1 RhIand IrIcomplexes of 4 (5-7) are cleanly formed in solution, all attempts to isolate them in pure form failed due to stability problems. However, crystalline solids of [Mo(κ1Ge-4)2(CO)4] (8) and [W(κ1Ge-4)2(CO)4] (9) were isolated and fully characterized by common spectroscopic techniques (8 by X-ray diffraction). DFT calculations were performed on a series of model compounds to elucidate a conceivable interplay between the metal atoms in neutral and cationic bimetallic complexes of the type [Rh(κ1E-qE)(CO)2Cl]0/+(qE=[Fc(NPh)2E] with E=C, Si, Ge). The bonding characteristics of the coordinated Fc-based metalloligands (qE/qE+) are strongly affected upon in silico oxidation of the calculated complexes. The calculated Tolman electronic parameter (TEP) significantly increases by approximately 20 cm-1(E=C) to 25 cm-1(E=Si, Ge) upon oxidation. The change in the ligand-donating abilities upon oxidation can mainly be attributed to Coulombic effects, whereas an orbital-based interaction appears to have only a minor influence.
authors.affiliation: Institute of Inorganic Chemistry, Karlsruhe Institute of Technology (KIT), Engesserstr. 15, 76131, Karlsruhe, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Walz
authors.affiliation: Institute of Inorganic Chemistry, Karlsruhe Institute of Technology (KIT), Engesserstr. 15, 76131, Karlsruhe, Germany.
authors.forename: Eric
authors.initials: E
authors.lastname: Moos
authors.affiliation: Institute of Inorganic Chemistry, Karlsruhe Institute of Technology (KIT), Engesserstr. 15, 76131, Karlsruhe, Germany.|Institute of Organic Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany.
authors.forename: Delphine
authors.initials: D
authors.lastname: Garnier
authors.affiliation: Institute of Inorganic Chemistry, Karlsruhe Institute of Technology (KIT), Engesserstr. 15, 76131, Karlsruhe, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Köppe
authors.affiliation: Institute of Inorganic Chemistry, Karlsruhe Institute of Technology (KIT), Engesserstr. 15, 76131, Karlsruhe, Germany.
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Anson
authors.affiliation: Institute of Inorganic Chemistry, Karlsruhe Institute of Technology (KIT), Engesserstr. 15, 76131, Karlsruhe, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Breher
keywords: carbene ligands; ferrocene; germylene; metalloligands; redox-active ligands