Intramolecular rearrangement of organosilyl groups between oxygen and nitrogen in aminosiloxanes: A joint experimental–theoretical study

Lithium amino-di-tert-butysilanolate reacts with halosilanes to give 1-silylamino-1,3-siloxanes (1–4). The tetrakis(1-silylamino)siloxane 4 thermally condenses yielding a spiocyclic six-membered ring (5) and NH3. Lithium salts of animo-disiloxanes form silylamino-silanolates or amido-disiloxanes. The first includes a 1,3-silyl group migration from the oxygen to the nitrogen atonm. The energies of the isomeric lithium salts of model compunds are calculated. Exemplary crystal structures are presented. (SiOSiN)-four- or eight-membered rings (6,7) are thermally obtaines by LiF-elimination from fluoro containing salts. In further reactions of lithiated animo-disiloxanes with halosilanes isomeric 1-silylamino-1,3-disiloxanes can be obtaines (15,16). The 1,3-silyl group migration can sterically (9) or electronically (10–14) be prevented. The most stable lithium salts of 1-silylamino-1,3-disiloxanesform amides. This explains that in further reactions with halosilanes, the new ligand is bonded wo the nitrogen atom (23–25). In results of crystal structure determinations new lithium-1-fluorosilylamio-1,3-disiloxanes (19–21) are presented. 19 crystallizes as tricyclic, 20 as an unknown pentacyclic, and 21 as monomeric compound. In 21, the shortest Si-N bond length (157.9 pm) with four coordinate silicon is found.