Synthesis and electronic structure of dissymmetrical, naphthalene-bridged sandwich complexes [Cp′Fe(μ-C_(10)H_8)MCp*] ~x (x = 0, +1; M = Fe, Ru; Cp′ = η~5-C _5H_2-1,2,4- t Bu_3; Cp* = η~5-C_5Me_5)

摘要

The dissymmetrical naphthalene-bridged complexes [Cp′Fe(μ-C _(10)H_8)FeCp*] (3; Cp* = η~5-C _5Me_5, Cp′ = η~5-C_5H _2-1,2,4-tBu_3) and [Cp′Fe(μ-C_(10)H _8)RuCp*] (4) were synthesized via a one-pot procedure from FeCl_2(thf)_(1.5), Cp′K, KC_(10)H_8, and [Cp*FeCl(tmeda)] (tmeda = N,N,N′,N′- tetramethylethylenediamine) or [Cp*RuCl]_4, respectively. The symmetrically substituted iron ruthenium complex [Cp*Fe(μ-C _(10)H_8)RuCp*] (5) bearing two Cp* ligands was prepared as a reference compound. Compounds 3-5 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 3-5 can be oxidized to monocations 3~+-5~+ and dications 3~(2+)-5 ~(2+). The chemical oxidation of 3 and 4 with [Cp_2Fe]PF _6 afforded the paramagnetic hexafluorophosphate salts [Cp′Fe(μ-C_(10)H_8)FeCp*]PF_6 ([3]PF_6) and [Cp′Fe(μ-C_(10)H_8) RuCp*]PF_6 ([4]PF_6), which were characterized by various spectroscopic techniques, including EPR and 57Fe M?ssbauer spectroscopy. The molecular structure of [4]PF_6 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.