Solid-State Structural Analysis of the “Naked” Isodicyclopentadienide Anion

Abstract

The crystallographically determined structural features of Na(isodiCp)(15-crown-5) and [K-cryptand(2.2.2)]+(isodiCp)- are compared to those of the corresponding Li(TMEDA) complex and the sandwich dimer involving Li+ (cocrystallized with Li(12-crown-4)2). The features of the potassium salt are distinctively different from those of its congeners. As a consequence of the encapsulation of the K+ ion by the cryptand, no interaction occurs with the isodiCp anion, which is “naked”. Notwithstanding the complete dissociation that exists, the stand-alone isodiCp anion exhibits appreciable folding about the bond that it shares with the norbornyl framework. The dihedral angle is 8.3(1)° in a downward direction away from the exo surface. This unrivaled opportunity to observe the free isodicyclopentadienide anion is shown to be in agreement with the results of HF−SCF calculations.

Fusing Rigid Spin Probes to Paramagnetic Sandwiches. Synthesis, Crystal Structures, and NMR Spectroscopy of Bis(isodicyclopentadienyl)metal Compounds

“…the angle α in Figure , G ), the interplanar angles ϑ (C8/9) and ϑ (C10) deviate from 120°, and the dihedral angles θ (C8/9) (Figure , F ) are considerably smaller than θ (C10). Similar features can be extracted from previous X-ray crystal data of other compounds containing the Isodicp ligand. 15c,

4 Molecular structures of (top) 3a + PF 6 - and (middle) 5a + PF 6 - . The H atoms were calculated for idealized C−H bonds.

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“…Cp π -Face Isomers. Ample preparative, structural, NMR, and computational evidence has been collected by Paquette, Gautheron, Gleiter, Bauer, and associates (see recent literature compilation in refs e and f) which demonstrates that at ambient temperature the isodicyclopentadienyl anion ( 2 ) is attacked by electrophiles preferably at the face next to the methano bridge ( exo -face). Therefore, it is not surprising that the exo , exo -isomer was obtained for all sandwich compounds of this work and that it was the predominating isomer when the exo , endo - and endo , endo -isomers were formed as well.…”

Ether and crown ether adduct complexes of sodium and potassium cyclopentadienide and methylcyclopentadienide—molecular structures of [Na(dme)Cp]∞, [K(dme)0.5Cp]∞, [Na(15-crown-5)Cp], [Na(18-crown-6)CpMe] and the “naked Cp–” complex [K(15-crown-5)2][Cp]

“…The distance from the Na cation to the cyclopentadienide centroid is 2.563 Å, this compares well to the mean of 1 (2.55 Å) and that of Na(15-crown-5) isocyclopentadienide (2.519 Å). 19 However, although the crown species relative to 1, they do promote the rationale that the smaller Na-C Cp distances seen in 1 and 5 are caused by the relative donor qualities of the bis(amine) donor; i.e. that the contraction results from the weaker Na-O interactions of poly-O Lewis bases relative to N-donors.…”

Magnesiation of Isodicyclopentadiene. Formation of Sandwich and Monomeric Complexes and the Stereoselectivity of Their Reactions with Transition Metal Halides

“…In the case of Na isodiCp, exposure to 15-crown-5 furnished pale green crystals of an exo monomeric complex similar to 5 but with the sodium ion now ligated to the crown ether . Extension to K isodiCp provided the opportunity to involve (2.2.2) cryptand.…”

“…Extension to K isodiCp provided the opportunity to involve (2.2.2) cryptand. The resulting purple-tinted crystals feature the potassium ion totally encapsulated by the cryptand, such that no interaction occurs with the naked isodiCp anion …”