Crystal structure of ferrocenophanyllithium: absence of an intramolecular C–H ⋯^–C hydrogen bond

Abstract

The previously inferred intramolecular [C-H-CIhydrogen bond in ferrocenophanyllithium from 1H NMR chemical shifts in solution is found to be absent in the solid state.We report results of an X-ray crystallographic study of ferrocenophanyllithium 1 (Fig. l), prepared from [l. llferrocenophane by abstraction of the C-1 proton by n-butyllithium and crystallized from a 2,5-dimethyltetrahydrofuran (DMTHF)-hexane solution. Crystals of lt are dark-red needles that decompose rapidly when isolated at ambient temperature, even under inert atmosphere. Special low temperature handling techniques2 have therefore been employed for isolating, selecting and mounting crystals of 1 for X-ray analysis.Previously, Mueller-Westerhoff and coworkers have, based on solution 1H NMR studies of the title compound and derivatives in tetrahydrofuran, claimed the 'first evidence for the existence of C-H-C hydrogen bonds'.3 Now, the solid state structure shows a long distance between the endo bridge

A Crystallographic and Computational Study of a Diethyl Ether Complex of Fluorenyllithium

“…The O1−Li1−O2 angle of 115° lies between a trigonal-planar and a tetrahedral geometry. Similar η 2 coordination geometries in organolithium chemistry have been observed, e.g., in the bis-quinuclidine complex of fluorenyllithium,7a ferrocenophanyllithium, and in some of the benzyllithium complexes mentioned. 8a,d,e

1 ORTEP drawing of the DEE complex of fluorenyllithium ( 1 ) showing the crystallographic numbering.

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Mechanism and Solvent Catalysis of the Degenerate 1,12-Metalations of [1.1]Ferrocenophanyllithium and [1.1]Ferrocenophanylsodium Studied by NMR Spectroscopy

“…In the preceding publication,3e general procedures for purification and handling of solvents and chemicals as well as preparation of precursors except for [11,12- 2 H 4 ][1.1]ferrocenophane 3b and their lithium salts have been reported together with NMR spectroscopy including transient 1D NOE experiments.…”

“…Typically 15 mg of [1.1]ferrocenophane was transferred to an NMR tube (cf. carbanion preparation) 3e…”

“…In preceding papers, we have presented results on the structure of 1 in the solution and in the solid state showing the absence of a [C−H−C] - hydrogen bond and the importance of ion pairing and solvation. Compound 1 has been found in the solid state as well as in solution to be a monomeric ion pair and to have a syn -structure with the lithium ion exo -coordinated.…”

Synthesis of New [14]Metallocenophanes

“…2,3 Examples of [1.1]ferrocenophanes with heteroatom bridges, [(C 5 H 4 ) 2 X] 2 Fe, with X ) SiMe 2 , 4-6 SnMe 2 , 7,8 Sn n Bu 2 , 7,8 SnI n Bu, 9 and PbPh 2 , 10 have also been reported. Aspects of carbon-bridged [1.1]metallocenophanes that have attracted interest include the isomerism and conformational flexibility possible in [1.1]ferrocenophane derivatives, 1,[11][12][13][14][15][16][17][18] the unusually stable carbanions formed by the deprotonation of [1.1]ferrocenophanes, [19][20][21][22] the stable carbocations formed by hydride abstraction from the bridges of [1.1]ferrocenophanes and ruthenocenophanes, 1, 23,24 the utility of [1.1]ferrocenophanes as hydrogen generation catalysts, [25][26][27][28] the unusual reversible oxidation of [1.1]ruthenocenophane, 29 and metal-metal interactions [30][31][32][33][34] in mono-and dioxidized [1.1]ferrocenophanes. [29][30][31][32][33][34] Although many studies have been concerned with [1.1]ferrocenophanes, relatively few [1 n ]metallocenophanes with n > 2 have been studied.…”