Silicon–nitrogen compounds. Part X. Dehydrofluorination of tetrafluorosilane–amine adducts with anionic hydrides and related compounds

Abstract

Adducts of tetrafluorosilane and secondary amines NHR,(R = Me or Et) react, especially when an excess of tetrafluorosilane is present, with the following dehydrofluorinating agents : LiAIH, (200") ; NaBH, (200') ; B2H6 (1 90-200") ; electropositive metals (350"). The products are corresponding substituted aminofluorosilanes Si F,-,(NR,), (R = Me, n = 1 or 2; R = Et, n = I ) . Tetrafluorosilane slowly reacts at 25" with alkali metals in liquid NHMe, to give SiF,(NMe,),.Similarly, SiF, and primary amines, on heating with LiAIH, (or in some cases NaBH4), produce corresponding N-substituted hexafluorodisilazanes (SiF,)%NR (R = H, Me, Et, Ph, or NMe,). In some cases, evidence for partly-substituted SiF,NHR or condensed SiF,NR(SiF, NR),SiF3 derivatives was obtained. The chief or sole product from SiF4-NH,R-B,H6reactions is a borazole B3H3N3R3: also the diamine NHMe[CH,],NHMe gives rise to HhNMeCH,CH,hMe. The adduct SiF,,ZNH,Me is not dehydrofluorinated when heated alone or with added NEt,, NH2Ph. zinc, or Fe(CO),; above 300" some disproportionation of the amine occurs. Physical properties of the products, including the mass spectrum of (SiF3),NH and i.r. spectra are reported : also possible intermediates in dehydrofluorination are discussed.