Reactive Sigma-Aryliron Complexes or Iron-Promoted Coupling of Two Phenyl Anions to One Bis(cyclohexadienylidene) Ligand: Synthesis, Structure, Mass Spectrometry, and DFT Calculations

A reaction of the bulky alkylcyclopentadienyliron(II) high-spin complex [Cp′′′Fe(μ-Br)]2 (1a) (Cp′′′ = C5H2(CMe3)3-1,2,4) with phenylmagnesium bromide produced the deep blue dinuclear complex [{Cp′′′Fe}2(μ,η5:η5-H5C6C6H5)] (2) with a bridging bis(cyclohexadienylidene) ligand. Its structural analysi...

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Bibliographic Details
Published in:	Organometallics Vol. 29; no. 4; pp. 806 - 813
Main Authors:	Wallasch, Mark W, Weismann, Daniel, Riehn, Christoph, Ambrus, Stefan, Wolmershäuser, Gotthelf, Lagutschenkov, Anita, Niedner-Schatteburg, Gereon, Sitzmann, Helmut
Format:	Journal Article
Language:	English
Published:	American Chemical Society 22-02-2010
Online Access:	Get full text
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Summary:	A reaction of the bulky alkylcyclopentadienyliron(II) high-spin complex [Cp′′′Fe(μ-Br)]2 (1a) (Cp′′′ = C5H2(CMe3)3-1,2,4) with phenylmagnesium bromide produced the deep blue dinuclear complex [{Cp′′′Fe}2(μ,η5:η5-H5C6C6H5)] (2) with a bridging bis(cyclohexadienylidene) ligand. Its structural analysis shows a centrosymmetric dimer. Each tri(tert-butyl)cyclopentadienyliron fragment is η5-coordinated to a cyclohexadienylidene moiety in which one carbon atom is bent out of the plane by 0.39 Å, exhibiting a bond length of 1.370 Å to its symmetry equivalent. Electrospray ionization mass spectra (ESI-MS) from acetonitrile solution confirm nicely the elemental composition of 2 by way of their isotope patterns. Reaction of 1a or its tetraisopropylcyclopentadienyl analogue [4CpFe(μ-Br)]2 (1b) (4CpC5H(CHMe2)4) with 2,6-diisopropylphenylmagnesium bromide affords the extremely air-sensitive, paramagnetic σ-aryl complexes [Cp′′′Fe(C6H3 iPr2)] (3a) or [4CpFe(C6H3 iPr2)] (3b), whose 4Cp−Fe distance of 1.92 Å is typical for cyclopentadienyliron high-spin complexes. In reactions with copper(I) halides 3a is rearranged to a diamagnetic π complex and coordinated via the ipso carbon atom of the six-membered ring to copper(I) halide fragments to form heterodinuclear complexes [Cp′′′Fe(μ,η5:η1-C6H3 iPr2)CuCl] (4-Cl) and [Cp′′′Fe(μ,η5:η1-C6H3 iPr2)CuBr] (4-Br). ESI mass spectra of complexes 4 do not show the molecular cations, but fragmentation to cyclopentadienyliron arene cations and formation of the hexa(tert-butyl)ferrocenium cation on one hand and fusion of complex fragments to oligonuclear complexes with or without inclusion of oxygen or fragments of solvent molecules on the other hand. Three of these oligonuclear complexes formed under the conditions of the ESI-MS experiment, whose elemental composition could be derived from isotope patterns, have been interpreted as [Cp′′′Fe(μ,η5:η1-C6H3 iPr2)Cu(μ,η1:η5-OC6H3 iPr2)FeCp′′′]+ and [{Cp′′′Fe(μ,η5:η1-C6H3 iPr2)Cu}2X]+ (X = Cl, Br). DFT calculations support the structural analysis of 2 and predict the structure of the dication 2 2+. The crystal structures obtained by X-ray diffraction for 2 and 3b are reported.
ISSN:	0276-7333 1520-6041
DOI:	10.1021/om900870j