Ansa‐Cycloheptatrienyl–Cyclopentadienyl Complexes

Abstract

Introduction of the Me2Si bridge and distortion of the sandwich structure facilitate the interaction of the 16‐electron ansa‐complex (see picture; blue Ti, yellow Si, gray C) with σ‐donor/π‐acceptor ligands, such as CO or isocyanides, which allows the electronic structure of this strongly bent first ansa‐cycloheptatrienyl–cyclopentadienyl transition‐metal complex to be studied. The complex is prepared from [(η‐C7H7)Ti(η‐C5H5)].

Photocontrolled Living Anionic Polymerization of Phosphorus‐Bridged [1]Ferrocenophanes: A Route to Well‐Defined Polyferrocenylphosphine (PFP) Homopolymers and Block Copolymers

“…We have explored photocontrolled living anionic ROP of the phosphorus-bridged 2 PR}] (R = alkyl groups, such as CMe 3 , CH 2 CMe 3 , and CH 2 SiMe 3 ) initiated by NaCp in THF at 5 8C, which provides access to well-defined polyferrocenylphosphines [Fe-A C H T U N G T R E N N U N G {(h-C 5 H 4 ) 2 PR}] n , with molecular weight control and narrow Table 3. Characterization data for PFP-b-PFS F diblock copolymers after sulfurization of the P III centers.…”

“…[2] In this context, polyferrocenylsilanes (PFSs) [3] in particular have been systematically studied. These materials have been shown to exhibit a range of interesting characteristics, such as a controlled response to a redox stimulus, thereby allowing their use in photonic crystal devices and as single-chain motors, [4] etch resistance to plasmas, [5] high refractive indices, [6] and to function as precursors to nanostructured magnetic ceramics [7] and carbon nanotube growth catalysts.…”

“…[15] These phosphorus-bridged [1]ferrocenophane derivatives were found to undergo ROP upon UV irradiation in polar solvents, such as THF and CH 3 CN, to yield PFPs in which the metal fragments ([M]) remained coordinated (Scheme 1a). Later, the same group reported the photolytic ROP 2 PPh}] when irradiated by UV light in THF at 0 8C, through a M À Cp bond cleavage mechanism affording PFPs with a broad molecular weight distribution (Scheme 1b). [16] In the work described, no externally added initiator was used and the polymerization was non-living with no control of molecular weight.…”

“…Moreover, with a moderately basic, delocalized cyclopentadienyl (Cp) anion as the initiator and propagating site, this "soft" living polymerization method is easier to perform in practice than the conventional procedures that use organolithium initiators and also allows for the controlled and living polymerization of functional monomers containing more sensitive functionalities. [17] We have also shown that this method can be used for the ROP of [2]dicarbaferrocenophanes, which had only previously been polymerized by using the thermal ROP method. [18] Scheme 1.…”

Synthesis and Solution Self‐Assembly of Polyisoprene‐block‐poly(ferrocenylmethylsilane): A Diblock Copolymer with an Atactic but Semicrystalline Core‐Forming Metalloblock

“…1 Thus, analogues of PFS with other elements in the bridge or containing different metals to iron (in some cases in combination with alternative π-hydrocarbon ligands) have been prepared and their ROP has been successfully demonstrated in a growing number of cases. This provides a route to new and fascinating metallopolymers with modified properties, 222,[399][400][401][402][403][404][405] and studies of these materials are likely to constitute a broad new area of future research.…”