ABINITIO MOLECULAR-ORBITAL STUDY ON THE REACTION OF TMA WITH H-2

The reaction of trimethylaluminium (Al(CH3)3, TMA) with H2 has been investigated using ab initio molecular orbital calculations. It has been shown that the activation energy of the reaction, TMA + H-2 --> AlH(CH3)2 + CH4, is about 1/2 of the dissociation energy of radical decomposition, TMA-->Al(CH3)2+CH3. This means that TMA decomposition under conditions where collisions between TMA and H-2 are sufficiently frequent is dominated by hydrogenolysis. This explains the experimental result that the decomposition temperature of TMA becomes lower with increasing H-2 pressure.