Teaching an old dog new tricks: new directions in fundamental and applied closo-carborane anion chemistry

Abstract

In this feature article we cover new directions in the fundamental and applied chemistry of the closo-carborane anions [HCB11H11]−1 and [HCB9H9]−1, including energy storage applications, ionic liquids, anionic carborane fused heterocycles/radicals, ligand substituents, and ligands for catalysis and coordination chemistry.

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

“…In the anionic moiety,t he Zn II center is coordinated by C cage ,atrimethylamine ligand and two chlorides,which act as bridging ligands towards aL i(THF) 2 unit. Important distances are d(C1 À Zn1) = 2.032 (7) , d(Zn1 À N1) = 2.094 (8) , d(Zn1 À Cl1) = 2.327(2) ,a nd d(Zn1ÀCl1) = 2.320 (2) .S imilar to 4,t he anion 5 is monomeric and well separated from the [Li-(THF) 4 ] + cation.…”

“…Themonocarborane [CB 11 H 12 ] À (1)isthe monoanion that results from the formal replacement of aboron vertex in the icosahedral closo-dodecaborate [B 12 H 12 ] 2À by ac arbon atom (Figure 1a). [1,2] Polyhedral boranes and carboranes possess unique steric and electronic properties that set them apart from traditional organic or inorganic building blocks.T heir delocalized bonding and sphere-like distribution of the electron density give rise to remarkable chemical and thermal stability,i ncluding low toxicity.C arborane 1 and its halogenated and/or methylated derivatives are best known as weakly coordinating anions;related to this property,areas of application are the isolation of reactive intermediates and Lewis-acid catalysis. [3] More recently, 1 has also become ab uilding block for coordination [4] and supramolecular [5] chemistry,t he synthesis of fused 3D/2D heterocycles, [6] as well as luminescence [7] and materials science.…”

Recent Progress in the Synthesis of the Monocarba‐closo‐dodecaborate(−) Anions

“…We also investigated the coordinating availability of 41 and 42 as WCAs using the methodd evelopedb yR eed et al and found that the coordinating availability of 41 was decreased that of [B 12 H 12 ] 2À 43,[ CB 11 H 6 Cl 6 ] À 2b,a nd wasc omparable to that of [CB 11 HCl 12 ] À 3b,o ne of the most widely used WCAs in the solid state (Table 3). [27] Even more surprisingly,d espite the fact that iodonium species are generally reactive/sensitive, the newly synthesized "clacker"-shapeda nion 42 showedh ighc hemical stability under various conditions in which the corresponding carboranyl(phenyl)iodonium 44 was convertedt oB 12 substituted C1 carborane anion derivatives 45 a-c (Scheme 14).…”

“…Developments of synthetic methods and functionalized molecules often go hand-in-hand. In this context, the monocarbacloso-dodecaborate(À)a nion [CB 11 H 12 ] À (1;d enoted here as "C1 carborane anion", Figure 1) has recently received increasing attention because of its unique structure andp roperties. [1] It is ar igid clusterm olecule composed of one carbon atom and eleven boron atoms, and forms ah ighly stable monochargedanion, because the negative charge is spread through-out the molecule through s-bonds.A saresult,i ts hows extremely high chemical, thermal, andp hotochemical stability.…”

“…In regard to other applicationso f1,avery recent review by Lavallo et al describes the fundamental and applied chemistry of 1 in coordination chemistry and materials science (battery electrolytesetc.). [11] Recent Advances in Synthetic Chemistry at the Carbon Vertex:V ersatile Cross-Coupling Reactions Before we developed cross-coupling reactionm ethodology at the carbon vertex, there had been only af ew methods to introduce aromatic rings, and they lackedv ersatility and practicality.T hat is, it was necessary to use either the C1 carborane anion precursor (6,[ nido-B 11 H 14 ] À )( Scheme 1A)o rp ermethylated C1 carborane anion (7,[ closo-CB 11 HMe 11 ] À )( Scheme 1B)a sa substrate. [12] In addition, the reaction conditions were severe, and the functional group tolerance was low.…”