Monomeric Chelated Amides of Aluminum and Gallium: Volatile, Miscible Liquid Precursors for CVD
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R-NM M Me 2 N
MNMe NMe 2
Figure 1. The general formula of a series of group 13 chelated amides designed to be low viscosity, monomeric liquids. M = Al or Ga and R = Me or Et. Recently, the compound (Me 2NCH 2CH 2NMe)AI(NMe 2)2 was synthsized.4 Unfortunately, there was no physical characterization nor reactivity reported for this material, and its extent of 83 Mat. Res. Soc. Symp. Proc. Vol. 606 © 2000 Materials Research Society
oligomerization was not addressed. This work will expand what is known about this compound, as well as exploring other diamine ligands and examining similar reactivity for gallium. EXPERIMENTAL AND RESULTS All syntheses were performed using standard Schlenk techniques. All NMR spectra were taken on either a Bruker AM 500 MI-Hz or a Bruker AM 300 MHz NMR spectrometer. Diethylether was dried over Na/K alloy and used freshly distilled. Both diamines were purchased from Aldrich Chemical Company and distilled before use. The hexakis(dimethylamido)digallium was made according to the seminal literature preparation'; the hexakis(dimethylamido)dialuminum was a gift from Aldrich Chemical Company. Transamination from the starting material [M(NMe 2)31 2 (where M = Al, Ga) proved to be facile. The reaction occurred at room temperature under stirring for both [AI(NMe 2)3 ]2 and [Ga(NMe 2)3] 2. [M•4Me 2)312 +(Me) 2NCH 2 CH 2NH(R) -4 [(Me) 2NCH 2CH 2NR]M(NMe 2)2 + HNMe 2
(1)
The syntheses were performed neat, with the diamine initially behaving as the solvent and the liquid product acting as the solvent towards the end of the reaction. Synthesis of AI(N(CHa
CH2_CH_
3)2_)fN(CH3)2_)2_(1.
In a 100-mL flask, [AI(N(CH 3)2)312 (2.0 g, 12.6 mmol) and (CH 3)2NCH 2CH 2NH(CH 3) (1.63 mL, 12.6 mmol) were mixed, and the clear, slightly orange solution was stirred overnight. Volatile materials were removed in vacuo, and clear, colorless 1 (2.54 g, 88 % yield) was distilled out at 65-70 'C at 300 mTorr with the distillation condenser just above ambient temperature. C: 51.76% found, 52.14% calc., H: 11.82% found, 11.92% calc., N: 24.32% found, 23.92% calc. 1H NMR: (2.85 ppm, singlet, 12H), (2.70 ppm, double doublet, 2H), (2.15 ppm, double doublet, 2H), (2.03 ppm, singlet, 3H), (1.75 ppm, singlet, 6H) When N,N,N '-trimethylethylenediamine (H3meda) was added to solid [AI(NMe 2)3]2 at room temperature, a slightly orange, clear liquid formed immediately with effervescence. After stirring over night at room temperature, 1 was distilled off in high yield between 65-70 'C. It was a clear, colorless liquid that froze around 26 'C (Table I). Compound 1 crystallized from the melt, and a single crystal X-ray diffraction study revealed the material to be a monomer with two molecules in the unit cell. Of the nitrogen-aluminum bonds, three were within the range 1.8051.810 A, which is expected for a covalent bond. The dative bond from the tertiary amine in the diamine was longer (2.036 A). Compound 1 was found to be a monomer in solution by using the melting point depression ofp-xylene. The molecular complexity that is reported
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