New reactivity at the silicon bridge in sila[1]ferrocenophanes

We describe two new types of reactivity involving silicon-bridged [1]ferrocenophanes. In an attempt to form a [1]ferrocenophane with a bridging silyl cation, the reaction of sila[1]ferrocenophane [Fe(η-C 5 H 4 ) 2 Si(H)TMP] ( 12 ) (TMP = 2,2,6,6-tetramethylpiperidyl) towards the hydride-abstraction reagent trityl tetrakis(pentafluorophenyl)borate ([CPh 3 ][B(C 6 F 5 ) 4 ]) was explored. This yielded the unusual dinuclear species [Fe(η-C 5 H 4 ) 2 Si(TMP·H)(η-C 5 H 3 )Fe(η-C 5 H 4 )Si(H)TMP][B(C 6 F 5 ) 4 ] [13][B(C 6 F 5 ) 4 ] in low yield. The formation of [13] + is proposed to involve abstraction of hydride from the silicon bridge in 12 with subsequent C-H bond cleavage of a cyclopentadienyl group by the resulting electrophilic transient silyl cation intermediate. We also explored the reaction of dimethylsila[1]ferrocenophane [Fe(η-C 5 H 4 ) 2 SiMe 2 ] ( 1 ) with the Au( i ) species AuCl(PMe 3 ). This was found to result in addition of the Au-Cl bond across the Cp ipso -Si bond to yield the ring-opened species [1′-(chlorodimethylsilyl)-ferrocenyl](trimethylphosphine)gold( i ), [Fe(C 5 H 4 SiMe 2 Cl){C 5 H 4 Au(PMe 3 )}] ( 14 ). This represents the first example of ring-opening addition of a metallocenophane with a reagent possessing a transition metal-halogen bond. Two new types of reactivity involving silicon-bridged [1]ferrocenophanes are described.