Synthesis, structures, and reactions of 1,2,3-tris(diethylamino)-1,2,3,4-tetrakis(1,1,2-trimethylpropyl)cyclotetrasilanes

The reaction of dichloro(diethylamino)thexylsilane (thexyl = 1,1, 2-trimethylpropyl) with lithium gave 1,2,3-tris(diethylamino)-1 ,2,3,4-tetrathexylcyclotetrasilane (2) as a mixture of four diastereomers (r-1,t-2,c-3,t-4-2, r-1,t-2,t-3,t-4-2, r-1,t-2,c-3,c-4-2, and r-1,c-2,t-3,t-4-2). The isomers were separated and identified by H-1, C-13, and Si-29 NMR, IR, Mass, and UV spectroscopy. The structures of r-1,t-2,c-3,t-4-2, r-l,t-2,t-3,t-4-2, and r-l,t-2,c-3,c-4-2 were confirmed by X-ray crystallography, The Si-Si bond lengths are 2.391(1)-2.499(2) Angstrom for r-1,t-2,c-3,t-4-2, 2.389(2)-2.478(1) Angstrom for r-1,t-2, t-3,t-4-2, and 2.397(2)-2.485(2) Angstrom for r-1,t-2,c-3,t-4-2. In these molecules, there is a significant change in the structures of the Si-4 frameworks; the dihedral angles were 18 degrees for r-1,t-2,c-3,t-4-2, 34 degrees for r-1,t-2,t-3,t-4-2, and 3 degrees for r-1,t-2,c-3, t-4-2. The chlorodeamination or bromodeamination of 2 with HCl or HBr afforded 1,2,3-trichloro-1,2,3,4-tetrathexylcyclotetrasilane or 1,2,3-tribromo-1,2,3,4-tetrathexylcyclotetrasilane, respectively. Also, a tetrachlorocyclotetrasilane, 1,2,3, 4-tetrachloro-1,2,3,4-tetrathexylcyclotetrasilane was obtained via cyclotetrasilanyllithium.