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).

Graphical abstractReaction 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 full-size imageDownload as PowerPoint slide