Kinetics and thermodynamics of the Al + trimethylaluminum reaction

Equilibrium between Al atoms, trimethylaluminum (TMA), and an Al–TMA complex has been observed over the temperature range 341–396 K at 50 Torr total pressure. Rate constants for the forward reaction are reported from 296 to 396 K. A vanʹt Hoff plot of the equilibrium constant versus 1/T yields ΔH0 and ΔS0 values for the complexation reaction as −19.6 (±1.7) kcal mol−1 and −27.7 (±4.8) cal mol−1 K−1, respectively. An MP2 calculation gives ΔH0 of complexation as −12.6 kcal mol−1. A complex which contains an Al–Al bond semi-bridged by a methyl group is predicted by ab initio and DFT calculations.