Catalysis

Starting with the invention of Ziegler-Natta catalysis, organoaluminium compounds have a prominent role in the production of polyolefins, such as polyethylene and polypropylene. Methylaluminoxane, which is produced from TMA, is an activator for many transition metal catalysts.

Semiconductor applications

TMA is also used in semiconductor fabrication to deposit thin film, high-k dielectrics such as Al₂O₃ via the processes of chemical vapor deposition or atomic layer deposition. TMA is the preferred precursor for metalorganic vapour phase epitaxy (MOVPE) of aluminium-containing compound semiconductors, such as AlAs, AlN, AlP, AlSb, AlGaAs, AlInGaAs, AlInGaP, AlGaN, AlInGaN, AlInGaNP, etc. Criteria for TMA quality focus on (a) elemental impurities, (b) oxygenated and organic impurities.

Photovoltaic applications

In deposition processes very similar to semiconductor processing, TMA is used to deposit thin film, low-k (non-absorbing) dielectric layer stacks with Al₂O₃ via the processes of chemical vapor deposition or atomic layer deposition. The Al₂O₃ provides excellent surface passivation of p-doped silicon surfaces. The Al₂O₃ layer is typically the bottom layer with multiple silicon nitride (Si_xN_y) layers for capping.

Hydrolysis and related protonolysis reactions

Trimethylaluminium is hydrolyzed readily, even dangerously:

Al₂Me₆ + 3 H₂O → Al₂O₃ + 6 CH₄

Under controlled conditions, the reaction can be stopped to give methylaluminoxane:

AlMe₃ + H₂O → 1/n [AlMeO]_n + 2 CH₄

Alcoholysis and aminolysis reactions proceed comparably. For example, dimethylamine gives the dialuminium diamide dimer:^[7]

2 AlMe₃ + 2 HNMe₂ → [AlMe₂NMe₂]₂ + 2 CH₄

Reactions with metal chlorides

TMA reacts with many metal halides to install alkyl groups. When combined with gallium trichloride, it gives trimethylgallium.^[8] Al₂Me₆ reacts with aluminium trichloride to give (AlMe₂Cl)₂.

TMA/metal halide reactions have emerged as reagents in organic synthesis. Tebbe's reagent, which is used for the methylenation of esters and ketones, is prepared from TMA and titanocene dichloride.^[9] In combination with 20 to 100 mol % Cp₂ZrCl₂ (zirconocene dichloride), the (CH₃)₂Al-CH₃ adds "across" alkynes to give vinyl aluminium species that are useful in organic synthesis in a reaction known as carboalumination.^[10]

Adducts

As for other "electron-deficient" compounds, trimethylaluminium gives adducts R₃N.AlMe₃. The Lewis acid properties of AlMe₃ have been quantified.^[11] The enthalpy data show that AlMe₃ is a hard acid and its acid parameters in the ECW model are E_A =8.66 and C_A = 3.68.

These adducts, e.g. the complex with the tertiary amine DABCO, are safer to handle than TMA itself.^[12]

The NASA ATREX mission (Anomalous Transport Rocket Experiment) employed the white smoke that TMA forms on air contact to study the high altitude jet stream.

Synthetic reagent

TMA is a source of methyl nucleophiles, akin to methyl lithium, but less reactive. It reacts with ketones to give, after a hydrolytic workup, tertiary alcohols.