Improved and Scalable Synthesis of [Et₄N][closo-1-CHB₉H₉]

Abstract

The derivatives of the [closo-1-CHB9H9]− anion have attracted increasing attention in the fields of catalysis and materials exhibiting superionic conductivity. The Brellochs method is widely utilized to synthesize the derivatives of the [closo-1-CHB9H9]− anion. On the basis of this innovative method, we have further developed a facile method, which is rapidly scalable to 37 g, and its overall yield of [Et4N]­[closo-1-CHB9H9] is up to ca 80%. The facile synthetic method is straightforward without the isolation of the [Et4N]­[arachno-6-CH2B9H12] intermediate. The cation exchange for oxidation cluster closure to the [closo-2-CHB9H9]− anion is avoided; positional isomerism of [closo-2-CHB9H9]− to [closo-1-CHB9H9]− can be conducted without a solvent, and conversion is almost quantitative.

Polymorphism and solid solutions of trimethylammonium monocarboranes

“…[NH(CH 3 ) 3 ][CB 9 H 10 ] and [NH(CH 3 ) 3 ][(CB 8 H 9 ) 0.26 (CB 9 H 10 ) 0.66 (CB 11 H 12 ) 0.08 ] were synthesized via the Brellochs method in a two-step reaction starting from B 10 H 14 , see eqn (1)–(3). 67,70 The 11 B NMR spectra of [NH(CH 3 ) 3 ][CB 9 H 10 ] reveal a high purity, and all peaks can be assigned to [ closo -2-CB 9 H 10 − ] after initial precipitation and to the more stable configuration [ closo -1-CB 9 H 10 − ] after heating to 423 K in accordance with literature (Fig. 1a).…”

“…1a). 67 The 11 B NMR spectrum of [NH(CH 3 ) 3 ][(CB 8 H 9 ) 0.26 (CB 9 H 10 ) 0.66 (CB 11 H 12 ) 0.08 ] was assigned to a mixture of mainly [ closo -1-CB 9 H 10 ] − , [ closo -CB 8 H 9 ] − and minor amounts of [ closo -CB 11 H 12 ] − along with some minor unidentified boron-containing phases with resonances at −3.8, −10.9 and −31.3 ppm (Fig. 1a).…”

“…B–H stretching and bending modes are observed in the regions 2350–2650 cm −1 and 900–1300 cm −1 , respectively. 67,71 More narrow N–H stretching modes and well defined B–H stretch modes are observed for [NH(CH 3 ) 3 ][CB 9 H 10 ], reflecting a simpler local environment for the single-anion compound as compared to [NH(CH 3 ) 3 ][(CB 8 H 9 ) 0.26 (CB 9 H 10 ) 0.66 (CB 11 H 12 ) 0.08 ]. There are no absorption modes corresponding to O–H, indicating a complete removal of water during the drying procedure.…”

“…Synthesis of [arachno-6-CH 2 B 9 H 12 ] − was done according to previously reported methods. 65,67 Decaborane (B 10 H 14 , 2.4 g, 10 mmol, Katchem, >98%) was added to a solution of KOH (2.4 g, 42 mmol, Sigma-Aldrich, ≥85%) in H 2 O (30 mL) at 0 °C. Over a period of 1 h, HCHO (37% solution in water, stabilized with 10% CH 3 OH, 9 mL, 120 mmol, Sigma-Aldrich) was added dropwise.…”

A Simple and Efficient Way to Directly Synthesize Unsolvated Alkali Metal (M = Na, K) Salts of [CB11H12]−

“…Obviously, recent studies mainly focused on the synthesis for the [Me3NH] + salt of [CB11H12] − , while methods on the direct synthesis of alkali metal (M = Na, K) salts of the [CB11H12] − anion are still very limited, which is inconsistent with the great application of alkali metal (M = Na, K) salts of the [CB11H12] − anion. Recently, we improved the synthetic method of [Et4N][closo-1-CHB9H9] [26], and on the basis of our previous work on the condensation reaction of the B-H bond for the synthesis of polyhedral boranes [27][28][29][30] and the application of a dihydrogen bond in amine boranes [31][32][33], we developed a straightforward method for the synthesis of unsolvated potassium and sodium salts of the [26], and on the basis of our previous work on the condensation reaction of the B-H bond for the synthesis of polyhedral boranes [27][28][29][30] and the application of a dihydrogen bond in amine boranes [31][32][33], we developed a straightforward method for the synthesis of unsolvated potassium and sodium salts of the [CB 11 H 12 ] − anion. This method avoids the exchange of cation, significantly simplifies the reaction procedure and can be easily scaled-up.…”