Tris-dimethylaminophosphorus reactions at low pressure on GaP, InP and quartz surfaces

The decomposition of the phosphorus precursor tris-dimethylaminophosphorus (TDMAP), at low pressures (similar to 10(-4) Torr) has been studied by mass spectrometry. Three different surfaces were used: quartz, InP and GaP. For the three surfaces pyrolysis is 50% complete at approximately 820, 520 and 350 degrees C, respectively. The activation energy for decomposition on the GaP surface is 18.5 +/- 2.5 kcal/mol and for the quartz surface, 47.3 +/- 3.5 kca/mol. The principle reaction products are dimethylamine, methylmethyleneimine and methyleneimine. On the quartz surface decomposition appears to occur via homolysis of the parent molecule, producing dimethylaminyl radicals, which react subsequently to form the observed products. For the surface-catalyzed reactions an intramolecular reaction mechanism is proposed in which there is a transfer of a hydrogen atom from a methyl group to the nitrogen lone-pair on an adjacent ligand. This reaction would produce both dimethylamine and methylmethyleneimine.