The synthesis and polymerization behaviour of silicon-bridged [1]- and [2]ferrocenophanes with sterically demanding trimethylsilyl substituents attached to the cyclopentadienyl rings

Peckham, Timothy J.; Foucher, Daniel A.; Lough, Alan J.; Manners, Ian

doi:10.1139/v95-255

Cited by 24 publications

(24 citation statements)

References 17 publications

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“…(2)] can be modified to accommodate substituted cyclopentadienyl rings in preparing derivatives 20-26. [13,[86][87][88] Trends such as decreasing ring tilt and FeÀCp distances are associated with strengthened FeÀCp bonding as the Cp ligands become increasingly electron-rich on substitution of Cp hydrogen atoms for electron-donating groups. [17] Other effects, such as increased stability towards air and moisture, are observed when sterically bulky substituents are introduced, such as the tBu groups in 25 and 26.…”

Section: Ansa Complexesmentioning

confidence: 99%

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

2007

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The structures, bonding, and ring-opening reactions of strained cyclic carbon-based molecules form a key component of standard textbooks. In contrast, the study of strained organometallic molecules containing transition metals is a much more recent development. A wealth of recent research has revealed fascinating nuances in terms of structure, bonding, and reactivity. Building on initial work on strained ferrocenophanes, a broad range of strained organometallic rings composed of a variety of different metals, pi-hydrocarbon ligands, and bridging elements has now been developed. Such strained species can potentially undergo ring-opening reactions to functionalize surfaces and ring-opening polymerization to form easily processed metallopolymers with properties determined by the presence of the metal and spacer. This Review summarizes the current state of knowledge on the preparation, structural characterization, electronic structure, and reactivity of strained organometallic rings with pi-hydrocarbon ligands and d-block metals.

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Section: Ansa Complexesmentioning

confidence: 99%

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

2007

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“…However, previous attempts at polymerizing species with more than one silicon atom in the bridge (e.g., the [2]ferrocenophane Fe(η-C 5 H 4 ) 2 -(SiMe 2 ) 2 ) have been unsuccessful as a consequence of the smaller degree of strain present. 20,21 In this paper, as a follow up to our communication, 22 we report full details of an alternate approach toward the copolymerization of the cyclic silane 1 and the silicon-bridged [1]ferrocenophane 3 and studies of the properties of the resulting materials.…”

Section: Introductionmentioning

confidence: 99%

Ring-Opening Copolymerization of Cyclotetrasilanes and Silicon-Bridged [1]Ferrocenophanes: Synthesis and Properties of Polysilane−Poly(ferrocenylsilane) Random Copolymers

Rulkens¹,

Resendes²,

Verma³

et al. 1997

Macromolecules

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Novel poly(methylphenylsilane)-poly(ferrocenyldimethylsilane) copolymers 5a-d of varying monomer composition were prepared via the thermal ring-opening polymerization of a mixture of the strained cyclic tetrasilane [MePhSi]4 (1) and the silicon-bridged [1]ferrocenophane Fe(η-C5H4)2SiMe2 (3). The resulting materials were structurally characterized by 1 H and 29 Si NMR and also by gel permeation chromatography (GPC), pyrolysis mass spectrometry (MS), and cyclic voltammetry. GPC in THF indicated that the molecular weights of the polymers 5a-d were in the range Mn ) (2.0 × 10 4 )-(8.9 × 10 4 ) with PDI values of 2.4-3.5. Polymers 5a-c were photosensitive and GPC traces of 5a-c were studied both before and after irradiation of the sample with UV light (λ ) 340 nm). The formation of short chain oligo(ferrocenylsilanes) after irradiation was consistent with exclusive photodegradation of the polysilane segments and indicated that the copolymers were random in nature. Pyrolysis MS of 5a-c also supported a random structure. Cyclic voltammetric studies of 5a-c in CH2Cl2 showed the presence of the characteristic two reversible oxidation waves arising from oligo(ferrocenylsilane) segments with interacting iron atoms at E1/2 ) 0.00 and 0.23 V (relative to ferrocene/ferrocenium) and an irreversible oxidation with Ep(ox) ) 0.39 V arising from the polysilane segments. UV/vis spectroscopy showed that the σ-electrons in the oligosilane segments are delocalized and that λmax increased from 325 to 333 nm as the proportion of the cyclotetrasilane 1 in the initial monomer mixture increased. These values suggest that the oligosilane segments are relatively short and do not approach the limit corresponding to ca. 30 silicon atoms (Mn ) ca. 3 000), which levels off at 338 nm. Attempted anionic initiation of the copolymerization of 1 and 3 was unsuccessful and led exclusively to homopolymerization. Transition metal catalyzed copolymerization of 1 and 3 using PtCl2 resulted in a copolymer which was derived almost exclusively from 3. The charge transport properties of the representative copolymer 5d were also investigated. Films of pristine 5d were insulating (conductivity <10 -14 S cm -1 ) but after exposure to iodine the conductivity increased by a factor of 10 8 to (6.5-8.2) × 10 -6 S cm -1 . In comparison, the conductivities of iodineexposed films of poly(ferrocenyldimethylsilane) (4) and poly(ferrocenyldi-n-butylsilane) (7) were ca. 2 × 10 -4 S cm -1 . The hole mobility of 5d was studied by standard time of flight techniques and was found to be appreciable with a value of 4.0 × 10 -6 cm 2 /V s.

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“…[b] Three independent molecules in the unit cell. [18] [Fe(h 5 -C 5 H 4 ) 2 SiR 2 OSiR 2 ], R = Me or Ph 2.5(12) [45] [Fe(h 5 -C 5 H 4 ) 2 SiMe 2 (OSiMe 2 ) x ], x = 2 or 3 1.5(5) [45] [Fe(h 5 -C 5 H 4 ) 2 Pt(PEt 3 ) 2 SiMe 2 ] 11.6(3) [47] [Fe(h 5 5.9(6) [48] [Fe(h 5 11.4(7) [58] [(h 5 [54] SiMe{Co 2 (CO) 6 C 2 nBu} 19.51(19) [54] Si{Co 2 (CO) 6 C 2 nBu} 2 19.87(22) [54] SiMe{Mo 2 Cp 2 (CO) 4 C 2 Ph} 20.93(20) [54] SiMeCo(CO) 4 19.98(5) [55] SiMe{Ni 2 (Cp) 2 C 2 Ph} 21.21(21) [56] SiMe{Ni(dppe)C 2 Ph} [a] 20.38(10) [54] SiMe{Ni(dmpe)C 2 Ph} [a] 19.90(13) [54] [a] dmpe = 1,2-bis(dimethylphosphino)ethane.…”

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Polyferrocenylsilane‐Based Polymer Systems

Bellas¹,

Rehahn²

2007

Angew Chem Int Ed

290

207

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The study of metallopolymers has blossomed into a mature field over the last few decades. Especially, polyferrocenylsilane (PFS) chemistry has taken a tremendous leap and continues to raise intense interest. Since the discovery of thermal ring-opening polymerization (ROP) of sila[1]ferrocenophanes, PFSs have been also accessed by anionic, cationic, transition-metal-catalyzed, and photolytic anionic ROP methodologies. A plethora of synthetic strategies have been devised, enabling access to a wide variety of copolymers, polyelectrolytes, and nanostructured materials. The distinctive physical properties and functions of many PFS-based polymers have been explored, leading to their apt exploitation in technical applications. Therefore, it is conceivable that PFS-related platforms might be indispensable nano-objects in the near future, as they stand on the verge of a new generation of sophisticated materials.

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The synthesis and polymerization behaviour of silicon-bridged [1]- and [2]ferrocenophanes with sterically demanding trimethylsilyl substituents attached to the cyclopentadienyl rings

Cited by 24 publications

References 17 publications

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

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

Ring-Opening Copolymerization of Cyclotetrasilanes and Silicon-Bridged [1]Ferrocenophanes: Synthesis and Properties of Polysilane−Poly(ferrocenylsilane) Random Copolymers

Polyferrocenylsilane‐Based Polymer Systems

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