Poly(ferrocenylphosphines) (e.g.4) obtained from the ring‐opening polymerization (ROP) of [1]ferrocenophanes such asP‐phenylphospha[1]ferrocenophane,1, have potential applications as catalytic materials based upon the reactivity of the phosphorus lone pair.1,2,3Unfortunately, thermally induced ROP does not permit molecular weight control, and well‐defined polymers must be synthesizedvialiving anionic polymerization, a painstaking synthetic technique. Ideally, transition‐metal catalyzed ROP reactions, using capping agents to control molecular weight,4would be used to generate suitably tractable polymers, a process presenting much less of a synthetic challenge. The versatility of this approach has been demonstrated for a number of silicon‐bridged ferrocenophanes, where access to both block copolymers and poly(silaferrocenes) with comb and star architectures has been possible.5As expected, however, the P(III)‐bridged [1]ferrocenophanes do not undergo transition‐metal catalyzed ROP, presumably because the lone pair on phosphorus binds strongly to the catalyst's metal centre.We have previously reported that reaction of a P(III)‐ bridged [1]ferrocenophane with methyl triflate led to a phosphonium‐bridged system (7) that did undergo transition‐metal catalyzed ROP.6The work presented herein is part of an investigation into whether the phosphorus lone pair could be protected to allow a formally P(III)‐bridged ferrocenophane to be polymerized using transition‐metal catalysts. This approach has the advantage that subsequent deborylation of the poly(ferrocenylphosphine) borane adduct should be possible, for example by reaction with amines, thus providing a route to controlled molecular weight poly(ferrocenylphosphines).