The synthesis and structure of chiral compounds with two hypervalent silicon atoms, Si,Si′-substituted 1,2-bis(dimethylsilylmethyl)diacetylhydrazines

The multi-stage character of the reaction of 1,2-diacetylhydrazine bis-O,O′-trimethylsilyl derivative with ClCH₂SiMe₂Cl to give bis-(OSi)-1,2-bis(dimethylchlorosilylmethyl)-1,2-diacetylhydrazine (VIII) was established from NMR spectroscopy. Methanolysis of VIII in the presence of NEt₃ gives the Si,Si′-dimethoxy derivative (IX). The corresponding Si,Si′-difluoro derivative (XI) was obtained by treatment of IX with boron trifluoride etherate. The structure, the stereodynamic behaviour, and the exchange reactions of chiral molecules of VIII, IX and XI and their precursors have been studies by multinuclear NMR spectroscopy. Compounds VIII, IX, and XI are the first examples of substances that contain two hypervalent silicon atoms and an XSi(C)₃O coordination centre.