CO2 as an Oxygen Source for Polysiloxanes – Preparation, Crystal Structure and Thermal Decomposition of Two Novel Silylcarbamates

Diaminosilanes (CH3)2Si(NHR)2 1a, b are obtained from dichlorodimethylsilane and primary amines (R = n-hexyl, iso-propyl) in good yields. Bis-insertion of CO2 into the Si–N bonds of the aminosilanes quantitatively gives the silylcarbamates (CH3)2Si(OCONHR)2, 2a, b. Oligoand polydimethylsiloxanes 3a, b as well as N,N′-substituted ureas CO(NHR)2 4a, b are formed upon heating the silylcarbamates 2a, b to ∼ 150 ◦C. The results of comprehensive NMR analyses of the aminosilanes, the two novel bis-silylcarbamates, the siloxanes and the ureas, and of single-crystal structure analyses of 2a and 4b are presented. In the crystal the n-hexyl silylcarbamate 2a shows a similar molecular packing arrangement as the iso-propyl urea derivative 4b.