Synthesis and Ring‐Opening Polymerization of Highly Strained, Ring‐Tilted [2]Ruthenocenophanes

Abstract

Only an ethylene bridge braces the Cp2Ru unit in the first [2]rutheno‐cenophane. This leads to a highly strained molecular framework (shown on the right) and makes [2]ruthenocenophanes suitable starting materials for thermal ring‐opening polymerization to give poly‐(ruthenocenylethylene)s.

Strained Metallocenophanes and Related Organometallic Rings Containing π‐Hydrocarbon Ligands and Transition‐Metal Centers

“…The downfield shift of the signal assigned to the ipso carbon atom on the ruthenocene fragment of the zirconium-bridged [1]ruthenocenophane 69 is unusual for tilted ansa metallocenes, but consistent with the analogous [1]ferrocenophane (C ipso : d = 159.0 ppm). [28] Thermal ROP has been reported for ethane-bridged [2]ruthenocenophanes [153] and stanna [1]ruthenocenophanes [155] to yield high-molecular-weight polyruthenocenes.…”

Recent developments with strained metallocenophanes

“…Hydrogen atoms omitted for clarity. The a angle is 23.5(2) [12]. Figure used with permission from Ref.…”

Organometallic Polymers of the Transition Metals

“…[155] The insoluble homopolymer had a conductivity of 10 À3 O À1 Á cm À1 , while the copolymer prepared with norbornene had M w and M n values of 21 000 and 11 000, respectively. Thermal ROP of [2] [157][158][159] Cyclic voltammetric studies of these polymers showed that the ruthenium-based polymers underwent irreversible oxidation, while the iron-based polymers underwent reversible oxidation. [158] Oxidation of the poly(ferrocenylethylene) with tetracyanoethylene (TCNE) resulted in antiferromagnetic interactions.…”

“…Thermal ROP of [2] [157][158][159] Cyclic voltammetric studies of these polymers showed that the ruthenium-based polymers underwent irreversible oxidation, while the iron-based polymers underwent reversible oxidation. [158] Oxidation of the poly(ferrocenylethylene) with tetracyanoethylene (TCNE) resulted in antiferromagnetic interactions. [159] Unsymmetrical [2]ferrocenophanes have also been synthesized and ring-opened by Manners and coworkers.…”