Transition Metal-catalyzed ROP of Strained Metallocenophanes

A very convenient, transition metal-catalyzed ROP route to polymetallocenes from strained metallocenophanes was reported in 1995 [87, 88]. Various Rh , Pd , Pd , 

Studies have shown that unsymmetrical [Ijferrocenophanes, in which only one of the cyclopentadienyl rings is methyl-substituted, yield regioregular polyferroce-nylsilanes upon transition metal-catalyzed ROP, whereas thermal ROP of the same monomers yields regioirregular materials [69, 90j. 

Research has also focused on understanding the mechanism of the transition metal-catalyzed ROP reactions of [l]ferrocenophanes. A logical first step in the polymerization is insertion of the transition metal into the strained Cp-carbon-bridg-ing element bond in the ferrocenophane. Polymers 3.42 formed in the presence of hydrosilanes are believed to result from competitive oxidative-addition between the Si-H bond of the hydrosilane and the strained Cp-Si bond of the ferrocenophane at the catalytic center, followed by reductive elimination. Detailed work has indicated that colloidal metal is the likely catalyst in the ROP reactions [94]. 

Metal-catalyzed ROP has also been reported for a [2]ferrocenophane with a Ge-Ge bridge, whereas the analogous species with an Si-Si bridge resists polymerization [95]. The presence of weak Cp-Ge bonds may be important in the successful ROP observed in the former case. 

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Thermal ROP of silicon-bridged [1 Jferrocenophanes Thermal ROP of other strained metallocenophanes Living anionic ROP of strained metallocenophanes Transition metal-catalyzed ROP of strained metallocenophanes Other ROP methods for strained metallocenophanes Properties of polyferrocenylsilanes... 

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