Synthesis and crystal structures of novel silylsubstituted diphosphanes

• Sterically protected diphosphanes have been synthesized.
• Experimental data concerning stereochemistry correlates with DFT calculations.
• Solid state structures are reported for three novel diphosphanes.
• Distribution of products strongly depends on n-BuLi:educt ratios.

Reaction of two equivalents of lithium hypersilylphosphanide (hypersilyl, Hyp = tris(trimethylsilyl)silyl) with dichlorotetramethyldisilane at low temperatures gives [HypPH–SiMe2–]21, a compound with high steric protection on both phosphane functionalities. Dehydrogenation reaction of 1 with n-butyl lithium yields the dilithiated [2.1.1] bicyclic phosphanide salt [HypPLi–SiMe2–]22. The bicyclic structure is confirmed by NMR spectroscopy and X-ray diffraction analysis. As a major byproduct during the synthesis of 1 as well as via reaction of 2 with dichlorotetramethyldisilane, 1,4-diphospha-cyclosilahexane [HypP–(SiMe2)2–]23 is obtained. X-Ray diffraction analysis shows exclusive formation of the trans-conformer 3a in the solid state, which is supported by calculations at the level of density functional theory (DFT).

Reaction of a sterically protected diphosphane with n-butyl lithium leads to a bicyclic diphosphanide structure. The bicyclic structure, in which each lithium atom coordinates to only one solvent molecule, is retained in solution.Figure optionsDownload as PowerPoint slide