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Abstract Exploration of the reduction chemistry of the 2,2’‐bipyridine (bipy) lanthanide metallocene complexes Cp*2LnCl(bipy) and Cp*2Ln(bipy) (Cp* = C5Me5) resulted in the isolation of a series of complexes with unusual composition and structure including complexes with a single Cp* ligand, multiple azide ligands, and bipy ligands with close parallel orientations. These results not only reveal new structural types, but they also show the diverse chemistry displayed by this redox‐active platform. Treatment of Cp*2NdCl(bipy) with excess KC8resulted in the formation of the mono‐Cp* Nd(III) complex, [K(crypt)]2[Cp*Nd(bipy)2],1, as well as [K(crypt)][Cp*2NdCl2],2, and the previously reported [K(crypt)][Cp*2Nd(bipy)]. A mono‐Cp* Lu(III) complex, Cp*Lu(bipy)2,3, was also found in an attempt to make Cp*2Lu(bipy) from LuCl3, 2 equiv. of KCp*, bipy, and K/KI. Surprisingly, the (bipy)1−ligands in neighboring molecules in the structure of3are oriented in a parallel fashion with intermolecular C⋅⋅⋅C distances of 3.289(4) Å, which are shorter than the sum of van der Waals radii of two carbon atoms, 3.4 Å. Another product with one Cp* ligand per lanthanide was isolated from the reaction of [K(crypt)][Cp*2Eu(bipy)] with azobenzene, which afforded the dimeric Eu(II) complex, [K(crypt)]2[Cp*Eu(THF)(PhNNPh)]2,4. Attempts to make4from the reaction between Cp*2Eu(THF)2and a reduced azobenzene anion generated instead the mixed‐valent Eu(III)/Eu(II) complex, [K(crypt)][Cp*Eu(THF)(PhNNPh)]2,5, which allows direct comparison with the bimetallic Eu(II) complex4. Mono‐Cp* complexes of Yb(III) are obtained from reactions of the Yb(II) complex, [K(crypt)][Cp*2Yb(bipy)], with trimethylsilylazide, which afforded the tetra‐azido [K(crypt)]2[Cp*Yb(N3)4],6, or the di‐azido complex [K(crypt)]2[Cp*Yb(N3)2(bipy)],7 a, depending on the reaction stoichiometry. A mono‐Cp* Yb(III) complex is also isolated from reaction of [K(crypt)][Cp*2Yb(bipy)] with elemental sulfur which forms the mixed polysulfido Yb(III) complex [K(crypt)]2[Cp*Yb(S4)(S5)],8 a. In contrast to these reactions that form mono‐Cp* products, reduction of Cp*2Yb(bipy) with 1 equiv. of KC8in the presence of 18‐crown‐6 resulted in the complete loss of Cp* ligands and the formation of [K(18‐c‐6)(THF)][Yb(bipy)4],9. The (bipy)1−ligands of9are arranged in a parallel orientation, as observed in the structure of3, except in this case this interaction is intramolecular and involves pairs of ligands bound to the same Yb atom. Attempts to reduce further the Sm(II) (bipy)1−complex, Cp*2Sm(bipy) with 2 equiv. of KC8in the presence of excess 18‐crown‐6 led to the isolation of a Sm(III) salt of (bipy)2−with an inverse sandwich Cp* counter‐cation and a co‐crystallized K(18‐c‐6)Cp* unit, [K2(18‐c‐6)2Cp*]2[Cp*2Sm(bipy)]2 ⋅ [K(18‐c‐6)Cp*],10.
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Di(indenyl)beryllium
Abstract The bonding in beryllocene, [BeCp2], took decades to establish, owing to its unexpected mixed hapticity structure (i.e., [Be(η5‐Cp)(η1‐Cp)]). Beryllium complexes containing the indenyl ligand, which is a close relative of the cyclopentadienyl anion, but which is also known to exhibit its own bonding peculiarities (e.g., facile η5⇄ η3shifts), have remained unknown. Standard metathetical approaches to their synthesis (e.g., with K[Ind′] + BeX2in an ether solvent) give rise to intractable oils from which nothing identifiable can be isolated. In contrast, mechanochemical preparation, involving the solvent‐free grinding of BeBr2and potassium indenides, leads to the production of discrete (indenyl)beryllium complexes, including [Be(C9H7)2] (1) and [Be{1,3‐(SiMe3)2C9H5}Br] (2). The former displays η5/η1‐coordinated ligands in the solid state, but DFT calculations indicate that an η5/η5‐conformation is less than 5 kcal mol−1higher in energy.
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- Award ID(s):
- 1665327
- PAR ID:
- 10305151
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Angewandte Chemie International Edition
- Volume:
- 60
- Issue:
- 39
- ISSN:
- 1433-7851
- Format(s):
- Medium: X Size: p. 21174-21178
- Size(s):
- p. 21174-21178
- Sponsoring Org:
- National Science Foundation
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