Synthesis of New Silylated and N-Si-N bridged Urea Derivatives from Aminosilanes and Diisocyanates.

Urea derivatives of the general motifs R(N(SiMe)C(O)NRR) and [R(NC(O)NRR)SiMe] (R=difunctional organic linker, i. e., core of diisocyanate used; R,R= H,Pr; H,Ph; Et,Et) were synthesized by insertion of four different diisocyanates (1,6-HMDI, 2,4-TDI, 1,3-TMXDI and 4,4'-MDI) into aminotrimethylsilanes MeSiNRR and diaminodimethylsilanes MeSi(NRR). The products obtained were analyzed by NMR and IR spectroscopy. Insertion into aliphatic aminosilanes was found to be favored for primary over secondary amino groups. For insertion into 4,4'-methylenebis(phenylisocyanate) (4,4'-MDI), good results were obtained for silanes derived from secondary amines as well. Insertion into aminosilanes with aromatic N-bound substituents turned out to be kinetically inhibited. Elucidation of molecular structures of the products by crystallography and NMR spectroscopy revealed interesting differences in N-Si connectivity, caused by steric and electronic effects of the reactants and migration of -SiMe and -(SiMe)- moieties.