Synthesis of amino- and amido-aluminium derivatives and investigation of their dynamics in solution

Abstract

The salts Li[Al(C 4 H 8 N) 4 ]ؒnC 4 H 8 NH (n = 1, 2; C 4 H 8 NH = pyrrolidine) have been prepared and characterised in solution by 1 H-, 13 C-, 7 Li-and 27 Al-NMR spectroscopy. Their reaction with AlCl 3 (Cl/Li molar ratio = 3) affords the binary amido derivative [Al(C 4 H 8 N) 3 ] 2 , which, on turn, is reactive towards AlXAlternatively, the monochloro species Al(CH 3 ) 2 Cl-(C 4 H 8 NH) results from the reaction of Al(CH 3 ) 3 (C 4 H 8 NH) and AlCl 3 (C 4 H 8 NH) (CH 3 /Cl molar ratio = 2). The dichloro-methyl derivative Al(CH 3 )Cl 2 (C 4 H 8 NH) is obtained by reacting Al(CH 3 ) 3 (C 4 H 8 NH) and AlCl 3 (C 4 H 8 NH) (Cl/CH 3 molar ratio = 2). The Lewis adducts AlCl 3 (amine) n (amine = pyrrolidine, n = 1, 2; amine = N,N,NЈ-trimethylpropanediamine, n = 1) have been isolated when AlCl 3 was contacted with the stoichiometric amount of the amine. At variance with N,N,NЈ-trimethylpropanediamine, N,N,NЈ-trimethylethylenediamine and N,N,NЈ,NЈ-tetramethylethylenediamine react with AlCl 3 yielding the salt derivatives [AlCl 2 (amine) 2 ][AlCl 4 ]. The dynamic processes of the coordinated amine ligands of AlCl 3 (amine) n (amine = pyrrolidine, n = 1, 2; amine = N,N,NЈ-trimethylpropanediamine, n = 1) and [AlCl 2 (amine) 2 ][AlCl 4 ] (amine = N,N,NЈ,NЈ-tetramethylethylenediamine) have been investigated in solution by NMR spectroscopy.

Preparation, spectroscopic characterization, and deprotonation reactions of Si(NHR)4 (R = i-Pr, t-Bu, p-tolyl) — EPR identification of persistent radicals formed by oxidation of polyimidosilicates

“…As reported in the literature (19), treatment of SiCl 4 with an excess of tertbutylamine at room temperature results in the aminolysis of two silicon-chlorine bonds and the formation of 6a in 83% yield. Further treatment of 6a with an excess of t-BuNH 2 in boiling toluene resulted in the formation of 7, a colourless liquid, in 89% yield.…”

Direct syntheses and complete characterization of halide-free tetrakis(dialkylamino)silanes

“…Secondarily, both the HBr and HI by-products are slightly stronger acids than HCl, driving the non-aqueous acidbase equilibrium with excess amine further forward toward the ammonium precipitate, X À+ H 2 NR 2 [15]. Ultimately, the steric bulk of the halide versus the incoming amine may also be important since recombination of any proposed cationic intermediate [5] with the larger halide anions will be less favored with bulkier amino alkyl groups [16][17][18]. The first attempts (1) using either SiBr 4 or SiI 4 with Li +À N(CH 3 ) 2 (since dimethylamine is a gas we chose the alkali metal salt) afforded the desired homoleptic Si(DMA) 4 in >70% yield and analytical purity after a simple reduced-pressure distillation.…”

“…The primary motivation for using the heavier halides was to exploit the decreasing Si-X bond strengths when compared to Si-Cl; we felt this would be particularly important and advantageous in achieving complete amination if the substitution steps involved a dissociative mechanism, as proposed by Passarelli [5], further facilitated by anomeric effects [12] of the nitrogen lone-pair [13,14]. Secondarily, both the HBr and HI by-products are slightly stronger acids than HCl, driving the non-aqueous acidbase equilibrium with excess amine further forward toward the ammonium precipitate, X À+ H 2 NR 2 [15].…”

“…Essential to both processes is the availability of high-purity chemical sources that display appropriate chemistry and appreciable volatility [1,2]. One general precursor class that has recently generated significant commercial [3] and scientific [4] interest are heteroand homoleptic pnictogenyl compounds of group 14 elements, of which tetrakis(dialkylamino)silanes are an important subset.These compounds -recognized to always contain various levels of halide impurity typically resulting from incomplete amination of the SiCl 4 starting material [3,[5][6][7] -are under active exploration as silicon sources for binary oxides (SiO 2 ) and higher-order silicates such as Zr x Si 1Àx O 2 and Hf x Si 1Àx O 2 [8][9][10]. Apart from their use as gate dielectric precursors in vapor and liquid delivery solutions, they have also been considered promising metal-organic sources for IV/V films; specifically the growth of amorphous silicon nitride [6,7,11] whose expanding applications range from semiconductor diffusion barriers and passivation layers to antireflection coatings on silicon solar cells.…”

“…These compounds -recognized to always contain various levels of halide impurity typically resulting from incomplete amination of the SiCl 4 starting material [3,[5][6][7] -are under active exploration as silicon sources for binary oxides (SiO 2 ) and higher-order silicates such as Zr x Si 1Àx O 2 and Hf x Si 1Àx O 2 [8][9][10]. Apart from their use as gate dielectric precursors in vapor and liquid delivery solutions, they have also been considered promising metal-organic sources for IV/V films; specifically the growth of amorphous silicon nitride [6,7,11] whose expanding applications range from semiconductor diffusion barriers and passivation layers to antireflection coatings on silicon solar cells.…”