Silylene-Bridged Dinuclear Iron Complexes [Cp(OC)₂Fe]₂SiX₂ (X = H, F, Cl, Br, I). Synthesis, Molecular Structure, Vibrational Spectroscopy, and Theoretical Studies

Abstract

The mu2-silylene-bridged iron complexes [Cp(OC)(2)Fe](2)SiX(2) (X = F (2), Br (4), I (5)) have been prepared from the mu2-SiH(2) functional precursor [Cp(OC)(2)Fe](2)SiH(2) (1) by hydrogen/halogen exchange, using HBF(4), CBr(4), and CH(2)I(2), respectively. The fluoro- and bromo-substituted derivatives 2 and 4 are converted upon UV irradiation to the carbonyl- and dihalosilylene-bridged dinuclear complexes [Cp(OC)Fe](2) (mu2-CO)(mu2-SiX(2)) (X = F (6), Br (7)) via CO elimination. All new compounds have been characterized spectroscopically, and, in addition, the molecular structure of 2, 4, and the previously reported chloro derivative [Cp(OC)(2)Fe](2)SiCl(2) (3) has been determined by single-crystal X-ray diffraction methods. For 1-5, the Fourier transform infrared and Raman spectra have been recorded and discussed, together with density functional theory calculations, which support the experimental results of the structural and vibrational analysis. The computed geometries, harmonic vibrational wavenumbers, and their corresponding Raman scattering activities are in good agreement with the experimental data. A significant dependence of the CO and Fe-Si stretching modes on the X substituents of the mu2-silylene bridge has been observed and discussed.

Photochemical Reaction of CpFe(CO)2SiMe3 (Cp = η5-C5H5) with a Trihydrosilane Containing a Bulky Amino Substituent, Bis(trimethylsilyl)aminosilane

“…Two of the three iron atoms are further bridged by a hydrosilylene ligand, HSiN(SiMe 3 ) 2 . The Fe−Si bond lengths (2.2830(6) and 2.2889(6) Å) in 4 are within the range of usual Fe−Si bond lengths found in silylene-bridged diiron complexes (2.25−2.36 Å). ,− , The C(1)−C(2) distance (1.410(3) Å) is comparable to those of alkyne-bridged triiron complexes: Fe 3 (CO) 9 (PPh 3 )(μ 3 -η 2 -CH 3 CCOC 2 H 5 ) (1.399(5) Å) and [Fe 3 (CO) 9 (μ 3 -η 2 -EtOCCPMePh 2 )] - (1.393(5) Å) . To our knowledge, this is the first example of the coupling of two carbon monoxide molecules by the reaction with hydrosilane to give an alkyne molecule.…”

“…The Fe−Fe distance of 2.6320(4) Å indicates the Fe−Fe single-bond character. The Fe−Si bonds (2.2771(5) and 2.2919(5) Å) are within the range of usual Fe−Si single bonds found in the known silylene-bridged diiron complexes (2.25−2.36 Å). ,− ,

2 ORTEP drawing of 3 (thermal ellipsoids at the 50% probability level). Hydrogen atoms are omitted for clarity.

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“…The Fe(1) atom was connected to the Fe(2) and Fe(3) atoms by Fe−Fe single bonds (Fe(1)−Fe(2) = 2.6589(4) Å, Fe(1)−Fe(3) = 2.6511(4) Å) and bridging carbonyl ligands, but there is no direct bond between Fe(2) and Fe(3) (Fe(2)···Fe(3) = 3.9611(4) Å). Three Fe−Si bond lengths are within the range of usual Fe−Si single-bond lengths (2.21−2.43 Å); ,− , however, the Fe(1)−Si(1) bond (2.3544(6) Å) is apparently longer than the others (Fe(2)−Si(1) = 2.2741(6) Å and Fe(3)−Si(1) = 2.2810(6) Å), suggesting that the bonding character of Fe(1)−Si(1) is different from the others. The geometry around the bridging silicon atom Si(1) is extremely distorted from a regular tetrahedral structure.…”

Reactions of Hydrosilanes with Transition Metal Complexes and Characterization of the Products

“…Structural data reported for silyl−transition metal complexes prepared from hydrosilanes that include both “classical” M−Si, M−H, and/or Si−H bonds and “nonclassical” M···H···Si interactions as well as silylene complexes (formed from hydrosilanes) are summarized in Table and includes entries from Tables , , and as well as additional complexes listed in the footnotes to these tables. Data for Si−TM bond distances reported for silyl−metal complexes prepared by routes that did not involve hydrosilanes and that have been reported in the Cambridge Data Base through Mar 2009 (version 5.30) are recorded in the footnotes to Table . …”

Iron‐Fragment‐Substituted Heterosiloxanes of Gallium [Cp(OC)2Fe−SiR2OGaR′2]2(R, R′ = Alkyl, Aryl) − Structures of [Cp(OC)2Fe−SiR2OGaMe2]2(R = Me, Ph)

“…The aggregation of 3e, due to GaϪO interaction, results in the formation of like and unlike diastereomers (Figure 1), as can be directly confirmed in solution by 1 H NMR spectroscopy (C 6 D 6 , Figure 2). Since the two diastereomers dif- fer in the topicities of their Ga-bonded methyl groups, the like diastereomer (RR/SS), which has a C 2 axis as symmetry element, provided free rotation around the OϪSi axis, and has homotopic methyl groups, while the unlike diastereomer (RS/SR), characterized by a mirror plane, has diastereotopic methyl groups.…”