title: Bis-Arene Complexes [Re(η6-arene)2]+as Highly Stable Bioorganometallic Scaffolds.
abstract: The synthesis of mono- and difunctionalized [Re(η6-C6H5R)(η6-C6H6-nRn)]+(n = 0, 1; R = COOH, Br) complexes starting from [Re(η6-benzene)2]+is described. The lithiation of [Re(η6-benzene)2]+with n-BuLi leads preferentially to the neutral, alkylated product [Re(η6-C6H6)(η5-C6H6-Bu)] but not to the expected deprotonation of the arene ring. Deprotonation/lithiation with LDA gave the mono- and the dilithiated products in situ. Their reactions with 1,1,2,2-tetra-bromoethane (TBE) or with CO2, respectively, gave [Re(η6-C6H5Br)(η6-C6H6)]+, [Re(η6-C6H5Br)2]+, or [Re(η6-C6H5COOH)(η6-C6H6)]+, [Re(η6-C6H5COOH)2]+. These functionalized derivatives of [Re(η6-benzene)2]+represent novel precursors for the synthesis of bioconjugates to bioactive structures, comparable to [Co(Cp)2]+or [Fe(Cp)2]. Different model compounds [Re(η6-C6H5R)(η6-C6H6-nRn)]+(n = 0, 1; R = -SCH2Ph, -NHPh, -CONHCH2Ph, -C6H5-COdpa) were synthesized via amide bond formation and nucleophilic aromatic substitution. These conjugates were fully characterized including X-ray structure analyses of most products. For all complexes, the1H NMR arene proton signals are strongly upfield-shifted as compared to those of the noncoordinated arenes. The electrochemical analyses show an irreversible, probably substituent-centered oxidation, which contrasts the cyclic voltammetry of the underivatized complexes where oxidation is fully reversible. The stability of the core and the reactivity of the substituents make these bis-arene complexes useful precursors in medicinal inorganic chemistry, comparable to cobaltocenium or ferrocene.
authors.affiliation: Department of Chemistry, University of Zürich , Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Meola
authors.affiliation: Department of Chemistry, University of Zürich , Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
authors.forename: Henrik
authors.initials: H
authors.lastname: Braband
authors.affiliation: Department of Chemistry, University of Zürich , Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
authors.forename: Paul
authors.initials: P
authors.lastname: Schmutz
authors.affiliation: Department of Chemistry, University of Zürich , Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Benz
authors.affiliation: Department of Chemistry, University of Zürich , Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Spingler
authors.affiliation: Department of Chemistry, University of Zürich , Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
authors.forename: Roger
authors.initials: R
authors.lastname: Alberto
mesh_terms: D001555:Benzene Derivatives / Q000737:chemistry*; D056831:Coordination Complexes / Q000737:chemistry*; D018360:Crystallography, X-Ray; D005296:Ferrous Compounds / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D000075163:Metallocenes / Q000737:chemistry; D008958:Models, Molecular; D010084:Oxidation-Reduction; D012428:Ruthenium / Q000737:chemistry*
chemical_list: D001555:Benzene Derivatives; D056831:Coordination Complexes; D005296:Ferrous Compounds; D000075163:Metallocenes; D012428:Ruthenium; C004998:ferrocene