om4005862_si_002.cif (217.54 kB)

Synthesis and Electronic Structure of Dissymmetrical, Naphthalene-Bridged Sandwich Complexes [Cp′Fe(μ‑C10H8)MCp*]x (x = 0, +1; M = Fe, Ru; Cp′ = η5‑C5H2‑1,2,4‑tBu3; Cp* = η5‑C5Me5)

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posted on 28.10.2013, 00:00 by Jennifer Malberg, Elizabeth Lupton, Eva-Maria Schnöckelborg, Bas de Bruin, Jörg Sutter, Karsten Meyer, František Hartl, Robert Wolf
The dissymmetrical naphthalene-bridged complexes [Cp′Fe­(μ-C10H8)­FeCp*] (3; Cp* = η5-C5Me5, Cp′ = η5-C5H2-1,2,4-tBu3) and [Cp′Fe­(μ-C10H8)­RuCp*] (4) were synthesized via a one-pot procedure from FeCl2(thf)1.5, Cp′K, KC10H8, and [Cp*FeCl­(tmeda)] (tmeda = N,N,N′,N′-tetramethylethylenediamine) or [Cp*RuCl]4, respectively. The symmetrically substituted iron ruthenium complex [Cp*Fe­(μ-C10H8)­RuCp*] (5) bearing two Cp* ligands was prepared as a reference compound. Compounds 35 are diamagnetic and display similar molecular structures, where the metal atoms are coordinated to opposite sides of the bridging naphthalene molecule. Cyclic voltammetry and UV/vis spectroelectrochemistry studies revealed that neutral 35 can be oxidized to monocations 3+5+ and dications 32+52+. The chemical oxidation of 3 and 4 with [Cp2Fe]­PF6 afforded the paramagnetic hexafluorophosphate salts [Cp′Fe­(μ-C10H8)­FeCp*]­PF6 ([3]­PF6) and [Cp′Fe­(μ-C10H8)­RuCp*]­PF6 ([4]­PF6), which were characterized by various spectroscopic techniques, including EPR and 57Fe Mössbauer spectroscopy. The molecular structure of [4]­PF6 was determined by X-ray crystallography. DFT calculations support the structural and spectroscopic data and determine the compositions of frontier molecular orbitals in the investigated complexes. The effects of substituting Cp* with Cp′ and Fe with Ru on the electronic structures and the structural and spectroscopic properties are analyzed.