A 3D Analogue of Phenyllithium: Solution‐Phase, Solid‐State, and Computational Study of the Lithiacarborane [Li−CB₁₁H₁₁]⁻

Abstract

The lithiacarborane [Li−CB11H11]− plays a central role in carborane chemistry, as it is a key intermediate to achieve the selective functionalization of the monocarba‐closo‐dodecaborate [CB11H12]− for applications in various fields. Also, it is an organometallic species of fundamental interest because it represents a 3D analogue of phenyllithium featuring an exo C−Li bond in addition to the delocalized negative endo charge of the spherical cluster. For the first time, the elusive and highly reactive endo/exo formal dianion [CB11H11]2− has been isolated as its lithiate as well as zincate in pure form and fully characterized. DFT calculations corroborate the experimental findings and underscore the remarkably high reactivity of the lithiacarborane. Subsequent derivatizations demonstrate the relevance of its initial clean formation.

Cesium carbonate mediated C–H functionalization of perhalogenated 12-vertex carborane anions

“…10 Additionally, deprotonation of the parent 12-vertex carborane anion [HCB 11 H 11 1− ] carborane with very strong bases ( i.e. n -BuLi or metal hydrides), 10 leads to the formation of the isolable 14,15 [CB 11 H 11 2− ] dianions that are nucleophilic but also very basic at carbon. 10 This basicity often leads to side reactions with the THF solvent, as well as elimination reactions, instead of clean nucleophilic substitution.…”

A 3D Analogue of Phenyllithium: Solution‐Phase, Solid‐State, and Computational Study of the Lithiacarborane [Li−CB11H11]−

“…The anionic part is displayed in Figure 2. [17] Key structural parameters are distances d(C1ÀLi1) = 2.113 (13) and d-(Li À O) = 1.992 (7) to 2.006 (7) .T he coordination modes of C1 and Li1 are hexacoordinate (pentagonal-pyramidal) for C1 and tetrahedral for Li, without dimer or aggregate formation. Furthermore,t he cage shows no significant distortion when compared to the parent [CB 11 H 12 ] À .T he observed bond lengths are similar to the ones found in 4, ar elated dicarbaboranyllithium, [18] and also monomeric aryllithium species containing bulky ortho substituents.…”

Free three-dimensional carborane carbanions

“…[34][35][36][37][38][39] Recently, Duttwyler and co-workers reported the synthesis and structural characterization of a lithiated anionic cluster Li[CB 11 H 11 ] − containing a lithium-carbon bond, which shed light on the structure of these nucleophilic intermediates and can be considered as a 3D analog of phenyllithium. 40 In this work, we report the synthesis, structural, and spectroscopic characterization of deprotonated discrete carboranyl anions, including [C 2 B 10 H 11 ] − , which, containing the "naked" carbanionic center, are the key intermediates in Cvertex functionalization of carboranes. (Scheme 1, bottom) These reactive species have been considered elusive for a number of years, yet the careful utilization of crown ethers yielded stable dissociated salts of three-dimensional carbanions.…”

“… 34–39 Recently, Duttwyler and co-workers reported the synthesis and structural characterization of a lithiated anionic cluster Li[CB 11 H 11 ] − containing a lithium–carbon bond, which shed light on the structure of these nucleophilic intermediates and can be considered as a 3D analog of phenyllithium. 40 …”