Preparation, crystal structure and thermal decomposition study of some trimethylsilyl esters of dicarbamic acids

Article abstract of DOI:10.1016/0022-328X(95)05833-B

Some new trimethylsilylated dicarbamic acid esters 1-9 and 10 were prepared. Their thermal decomposition was studied in n-alkanes as media. The reactions were monitored by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS), respectively. Some N-silylated cyclic ureas 11-15 were also prepared from the corresponding esters 2-6 by thermolysis. The crystal structures of 2, 5 and 8 are also discussed. The crystal and molecular structures of 2 and 5 have very similar characteristics. Both molecules are sited via their molecular centre of symmetry on crystallographic inversion centres. The carbamate groups are planar in all three cases as expected. An analysis of the data showed that the force due to Si-O conjugation which constrains the Si atom into the plane of the carbamate group is comparable to the crystal packing forces with a small out-of-plane movement being not unfavourable.