Preparation of Monomeric [LAl(NH₂)₂]—A Main‐Group Metal Diamide Containing Two Terminal NH₂ Groups

Abstract

Dedicated to Professor Dietmar Seyferth on the occasion of his 75th birthdayAluminum amides supported by organic ligands are important molecular precursors for the preparation of aluminum nitrides, such as Al À N based semiconductors and Al À N ceramics.[1] Amides with the general formula [R 2 Al(NH 2 )], in which R corresponds to an organic substituent, are rare. The presence of a reactive NH 2 group, which can be involved in further substitution reactions, may lead to mixed-metal imides that have the AlÀN(H)ÀM skeleton (M = metal atom). However the known amides show a strong tendency to oligomerize and form unstable trimers [{R 2 Al(m-NH 2 )} 3 ] (R = Me, tBu) [2a,b] or dimers [{R 2 Al(m-NH 2 )} 2 ] (R= Me 3 Si) [2b-d] because of the Lewis acidity of the aluminum center and the presence of the electron lone pair at the nitrogen atom of the NH 2 group. The steric bulk of the substituents is the major factor that determines the degree of association. However, the mechanism of the formation of the product remains unclear. The adducts of composition R 3 Al·NH 3 are thermodynamically unstable and thus decompose at elevated temperatures to the corresponding amides under elimination of alkanes. [2a, 4] So far there are no reports known on the preparation of aluminum amides by treating KNH 2 or NaNH 2

β‐Diketiminate Gallium Amides: Useful Synthons in Gallium Chemistry

“…The presence of the NH moiety was further confirmed by IR spectroscopy. In compounds 1-4 and 7, the corresponding vibrations were found in a narrow interval ν = 3371-3381 cm -1 , which is in a good agreement with the ν s vibration of the NH 2 group in LAl(NH 2 ) 2 (ν = 3396 cm -1 ) [21] and LGa(NH 2 ) 2 (ν = 3373 cm -1 ). [8] In cases of compounds 5 and 6, the matching vibrations were found at lower wavenumbers [ν = 3338 (for 5), 3335 cm -1 (for 6)].…”

“…This is supported by the planar environment of the N3 and N4 atoms in 4. The corresponding signal of the N-H proton in compounds 1-3 and 7 appears at lower field than the signal for the N-H protons in LAl(NH 2 ) 2 (δ = -0.52 ppm) [21] and LGa(NH 2 ) 2 (δ = -0.58 ppm), but at higher field compared to those in 5 and 6. The latter is caused by the presence of the chlorine atom attached to the same metallic center as the amino group.…”

Fluorine functionalized compounds of group 13 elements

“…Additionally, the steric property of the ligand works synergetically to its electronic factors offering an unique possibility to stabilize the low coordination number at the metal center or low oxidation states [31,[52][53][54]. The mono-and dihalides of Al and Ga synthesized recently by our group are interesting compounds and have been utilized to prepare the corresponding hydroxides [12,14], thiols [49], and amides [55]. Similarly we have also shown that the metathesis reaction of these compounds with suitable fluorinating agents can lead to the formation of the corresponding fluorine derivatives [56].…”

New route to alkylaluminum hydroxides via hydrolysis of cyclopentadienylaluminum complexes

“…These compounds were found to be stable at ambient conditions and successfully applied as precursors for heterobimetallic species and alumoxanes [10][11][12]. The reaction of (L)AlCl 2 or (L)Al(I)Cl with stoichiometric amounts of water in the presence of N-heterocyclic carbene was previously used for preparation of aluminum hydroxides such as (L)Al(OH) 2 and [(L)Al-(l-OH)Cl] 2 [13][14][15]. These very sophisticated and complicated procedures cause that the synthesis of hydroxyaluminum compounds still is considered as a challenge.…”