Direct Hydrogenation of Aluminum via Stabilization with Triethylenediamine: A Mechanochemical Approach to Synthesize the Triethylenediamine ⋅ AlH₃ Adduct

Abstract

Two approaches for the synthesis of the triethylenediamine (TEDA) · AlH 3 adduct have been discovered. Both, the mechanochemical procedure and the wet chemical method lead to crystalline products. Starting from metallic Al powder and TEDA, ball milling under a pressure of 100 bar H 2 facilitates a direct hydrogenation of aluminum with conversions up to 90 %. Structure determination from X-ray powder diffraction data revealed an 1-D-coordination polymer of the type [TEDAÀ AlH 3 ] n .Furthermore, solid-state NMR techniques have been applied to analyze composition and structure of the products. Due to the polymeric arrangement, an enhanced stability of the material occurred which was investigated by thermal analysis showing a decomposition located above 200°C. Overall, the stabilization of AlH 3 by TEDA holds promise for hydrogen storage applications.

Activation of Molecular Hydrogen by Inter‐ and Intramolecular Al−N Lewis Pairs

“…[13] Recently, the monomeric Al(I) compound Al(C 6 H-2,6-(C 6 H 2 -2,4,6-i Pr 3 ) 2 -3,5-i Pr 2 ) was described for hydrogen activation without the presence of a Lewis base. [14] Interestingly, it has been shown that aluminium metal can be mechanochemically hydrogenated in the presence of one equivalent of a triethylenediamine (TEDA) [15] or a transition metal catalyst and piperidine. [16] The CÀ H activation and hydroalumination of alkynes by the intramolecular AlÀ N compound (o-TMPÀ C 6 H 4 )AlH 2 ((2-(2,2,6,6tetramethyl-piperidin-1-yl)phenyl)-aluminium dihydride) have been previously reported.…”

“…Therein, the AlÀ N distance of 2.311(2) Å is significantly longer if compared to representative Al-N distances in similar compounds. Some selected representative compounds and their AlÀ N bond lengths are as follows, [Me 2 NÀ C 10 H 6 À AlH 2 ] 2 2.118(3) Å (hydride bridged dimer), [20] Me 3 NÀ AlMe 3 2.045(2) Å, [21] (Me 3 N) 2 AlH 3 2.163(2) Å, [22] [TEDAÀ AlH 3 ] n 2.161(2) Å (both AlÀ N distances are equal) [15] and TEDA-(AlMe 3 ) 2 2.065(8) Å. [23] FLPs and classic Lewis pairs can be discriminated by atomic distances.…”

Sustainability Assessment of Mechanochemistry by Using the Twelve Principles of Green Chemistry

“…Nevertheless, sublimation has also been used to remove volatile reactants used in excess in mechanochemical reactions, thus rendering pure nonvolatile product. For example, using this approach nonvolatile products such as the triethylenediamine (TEDA)⋅AlH 3 adduct, [23] and zeolitic imidazolate frameworks (ZIFs), [24] were easily isolated from their corresponding starting materials (Figure 3).…”

Aluminum hydride for solid-state hydrogen storage: Structure, synthesis, thermodynamics, kinetics, and regeneration

“…AlH 3 can react with a variety of organic compounds [119][120][121][122][123][124][125][126][127] . A variety of AlH 3 adducts of TMEDA (Me 2 NCH 2 CH 2 NMe 2 ), DIOX (O(CH 2 CH 2 ) 2 O), TEA (Et 3 N), BDMA (PhNMe 2 ), and TMPDA (Me 2 NCH 2 CH 2 CH 2 NMe 2 ) have been characterized by XRD, NMR, FT-Raman, FT-IR, DFT calculation, elemental analysis, and thermal analysis [126 , 127] .…”