Abstract
The ring‐opening reactions of a series of sila[1]ferrocenophanes with protic acids of anions with various degrees of noncoordinating character have been explored. Ferrocenyl‐substituted silyl triflates FcSiMe~2~OTf (5 a) and Fc~3~SiOTf (5 b) (Fc=(η^5^‐C~5~H~4~)Fe(η^5^‐C~5~H~5~)) were synthesized by means of HOTf‐induced ring‐opening protonolysis of strained sila[1]ferrocenophanes fcSiMe~2~ (3 a) and fcSiFc~2~ (3 b) (fc=(η^5^‐C~5~H~4~)~2~Fe). Reaction of 3 a and 3 b with HBF~4~ yielded fluorosubstituted ferrocenylsilanes FcSiMe~2~F (6 a) and Fc~3~SiF (6 b) and suggested the intermediacy of a highly reactive silylium ion capable of abstracting F^−^ from the [BF~4~]^−^ ion. Generation of the solvated silylium ions [FcSiMe~2~⋅THF]^+^ (7a^+^), [Fc~3~Si⋅THF]^+^ (7b^+^) and [FcSi__i__Pr~2~⋅OEt~2~]^+^ (7c^+^) at low temperatures, by reaction of the corresponding sila[1]ferrocenophanes (3 a, 3 b, and fcSi__i__Pr~2~ (3 c), respectively) with H(OEt~2~)(S)TFPB (S=Et~2~O or THF; TFPB=tetrakis[3,5‐bis(trifluoromethyl)phenyl]borate) was monitored by using low‐temperature ^1^H, ^13^C, and ^29^Si NMR spectroscopy. In situ reaction of 7a^+^, 7b^+^, and 7c^+^ with excess pyridine generated [FcSiMe~2~⋅py]^+^ (8a^+^), [Fc~3~Si⋅py]^+^ (8b^+^), and [FcSi__i__Pr~2~⋅py]^+^ (8c^+^), respectively, as observed by ^1^H, ^13^C, and ^29^Si NMR spectroscopy. A preparative‐scale reaction of 3 b with H(OEt~2~)(THF)TFPB at −60 °C and subsequent addition of excess pyridine gave isolable red crystals of 8b‐[TFPB]⋅CHCl~3~, which were characterized by ^1^H and ^29^Si NMR spectroscopy as well as by single‐crystal X‐ray diffraction.