Synthesis, Structures, and Properties of Strained, Silicon-Bridged [1]Ferrocenophanes with Methylated Cyclopentadienyl Rings

Pudelski, John K.; Foucher, Daniel A.; Honeyman, Charles H.; Lough, Alan J.; Manners, Ian; Barlow, Stephen; O’Hare, Dermot

doi:10.1021/om00005a051

Cited by 72 publications

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“…Compounds 9 and 11 were subjected to a cyclic voltammetric study in order to probe any electronic effect that the bis(phosphine)metal(II) fragments may have on the ferrocene/ferrocenium redox couple. The platinum-containing compound 11 exhibited an electrochemically reversible redox couple, as was previously reported for sila[1]-, [20] germa[1]-, [21] and stanna[1]ferrocenophanes, [5c] whereas oxidation proved irreversible in the case of 9. The most striking feature of each voltammogram was the oxidation potential, which occurred at À0.821 (E p ) and À0.682 V (E8) versus the ferrocene/ferrocenium redox couple (scan rate of 250 mV s À1 ) for compounds 9 and 11, respectively.…”

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confidence: 65%

“…In cases where the Cp rings are more firmly bound, deformation occurs preferentially at the Cp ipso-carbon atoms. [20] This is due to the higher energy penalty associated with tilting the Cp rings and is manifested structurally in higher b and lower a angles. In 9 and 11 the converse is true, with the b angles proving considerably less marked (25.5 and 25.98 for 9, and 26.4 and 26.28 for 11) than in 1 (M = Fe, ER x = SiMe 2 ) [both 37.0(6)8].…”

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confidence: 99%

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Strained Metallocenophanes with Late Transition Metals in the Bridge: Syntheses and Structures of Nickel‐ and Platinum‐Bridged [1]Ferrocenophanes

et al. 2008

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Until recently, few classes of strained rings containing transition elements had been explored, but these interesting species are now attracting substantial attention.[1] In particular, strained metallocenophanes (1) and related species containing p-hydrocarbon ligands (e.g. 2-5) [2] have been the focus of recent investigations due to the fascinating questions that surround their electronic structures, bonding, and reactivity. Furthermore, the ability of these compounds to yield functional metallopolymers by ring-opening polymerisation (ROP) has provided an extra impetus to the field. [3] The nature of the transannular bridge, ER x , in such species is of pivotal importance as the size and geometric preferences of the bridging element directly influence the strain present. Moreover, in the ring-opened polymers 6 the metal-metal interactions are modulated by the spacer unit.[4] To date, most work in the area of strained metallorings has involved [1]ferrocenophanes (e.g. 1, M = Fe) containing bridging nonmetallic main group elements E such as Si, P, and more recently S and B.[2a] The incorporation of main group metals (Sn, [5] Al, [2c, 6] and Ga [2c, 7] ) and early d-block metals (Ti, Zr, and Hf) [8] has also been successful. However, to date no transition metals other than the aforementioned Group 4 d 0 tetrahedral centers have been successfully introduced into the bridge. Herein, we report examples of [1]ferrocenophanes with the Group 10 metals Ni and Pt in the bridge, which leads to strained, unexpectedly electron-rich species containing square-planar d 8 centers. The scarcity of metal-bridged [1]ferrocenophanes is at first sight somewhat surprising, given that the main synthetic route to these molecules would appear applicable to any element for which a dichloride is available.[2a] We have found, however, that reaction of many transition-metal dihalides with dilithioferrocene-tmeda complex (tmeda = N,N,N',N'-tetramethylethylenediamine) results in reduction of the metal center. For instance, treatment of Li 2 [Fe(h 5 -C 5 H 4 ) 2 ]·tmeda (7) [9] with trans-[NiCl 2 (PMe 3 ) 2 ], [10] in hexane at À20 8C, only leads to the precipitation of metallic nickel. In striking contrast, the analogous reaction of 7 with trans-[NiCl 2 -(PnBu 3 ) 2 ] (8, Scheme 1) [11] resulted in a cloudy, dark red solution with a single new product detected by 31 P{ 1 H} NMR spectroscopy (d = 13.5 ppm, ca. 20 % conversion). Work-up afforded a dark red crystalline solid in modest yield (11 %) that was subsequently characterized as the first nickel-bridged [1]ferrocenophane [{Fe(h 5 -C 5 H 4 ) 2 }Ni(PnBu 3 ) 2 ] (9). [12] It is of interest that the Ni II component readily undergoes a trans-tocis isomerisation during the reaction and that no product containing the original trans configuration was observed.Compound 9 was fully characterized by 1 H, 13 C{ 1 H}, and 31 P{ 1 H} NMR spectroscopy. It is noteworthy that all three spectra displayed resonances at predictable chemical shifts and as such were consistent with the incorporation of a diam...

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Strained Metallocenophanes with Late Transition Metals in the Bridge: Syntheses and Structures of Nickel‐ and Platinum‐Bridged [1]Ferrocenophanes

et al. 2008

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“…FCPs [14] These values, compared with those of their nonmethylated counterparts, revealed that with increasing ring methylation, the tilt angle decreases significantly. Whereas the onset temperature for the thermal ROP increases by increasing the methylation level, the corresponding enthalpy DH ROP is not substantially affected, as revealed by differential scanning calorimetry (DSC) data.…”

Section: Ring-opening Polymerization Behavior Of Ansa Compoundsmentioning

confidence: 95%

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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“…(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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Synthesis, Structures, and Properties of Strained, Silicon-Bridged [1]Ferrocenophanes with Methylated Cyclopentadienyl Rings

Cited by 72 publications

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Strained Metallocenophanes with Late Transition Metals in the Bridge: Syntheses and Structures of Nickel‐ and Platinum‐Bridged [1]Ferrocenophanes

Strained Metallocenophanes with Late Transition Metals in the Bridge: Syntheses and Structures of Nickel‐ and Platinum‐Bridged [1]Ferrocenophanes

Polyferrocenylsilane‐Based Polymer Systems

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

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