From lithiumhalosilylamide to small and large ring compounds, iminosilenes and iminosilanes

Structure investigations on lithiumhalosilylamides have repeatedly yielded astonishing results. Depending on the solvents and the substitution of the nitrogen, they are isolated as acyclic, three- to penta-, bi-, and spiro-cyclic compounds. The shortest Si–N bond (157.9 pm) of four-coordinated silicon is found in these salts. The different formation of silicon–nitrogen containing rings by elimination of alkaline halides from halosilylamides depends on the solvent and structural make-up of the halosilylamides. Four- to 14-membered rings are formed. Four-membered SiN-rings with the smallest angles at the silicon (76°), and the cyclodisilazane dications are obtained. Stable iminosilenes and iminosilanes are isolated and unusual cycloaddition products are presented.