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(eta-C5H4)(2)-Si(H)TMP] (12) (TMP = 2,2,6,6-tetramethylpiperidyl) towards the hydride-abstraction reagent trityl tetrakis(pentafluorophenyl) borate ([CPh3][B(C6F5)(4)]) was explored. This yielded the unusual dinuclear species [Fe(eta-C5H4)(2)Si(TMP center dot H)(eta-C5H3)Fe(eta-C5H4)Si(H)TMP][B(C6F5)(4)] [13][B(C6F5)(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(eta-C5H4)(2)SiMe2] (1) with the Au(I) species AuCl(PMe3). 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(C5H4SiMe2Cl){C5H4Au(PMe3)}] (14). This represents the first example of ring-opening addition of a metallocenophane with a reagent possessing a transition metal-halogen bond.