Incorporation of a First Row Element into the Bridge of a Strained Metallocenophane: Synthesis of a Boron‐Bridged [1]Ferrocenophane

Braunschweig, Holger; Dirk, Regain; Müller, Mat­thias; Nguyen, Paul; Resendes, Rui; Gates, Derek P.; Manners, Ian

doi:10.1002/anie.199723381

Cited by 114 publications

(64 citation statements)

References 43 publications

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“…For example, 13 [25] 1,1'-di(methylgallyl)ferrocene: d = 76.2 ppm [32] ). This upfield shift is characteristic of strained [n]metallocenophanes (for example, 4, C ipso : d = 44-45 ppm; [15] 1,2-bis(dimethylamino)-1,2-dibora[2]ferrocenophane, C ipso : d = 76.2 ppm [19] ).…”

Section: Summary and Outlook 5077mentioning

confidence: 97%

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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: Summary and Outlook 5077mentioning

confidence: 97%

“…[13] 2.2.2. Group 13 Elements as Bridges Boron [14] The first reported boron-bridged ferrocenophanes 4 [15] prepared by Braunschweig and Manners [Eq. (3)] currently remain the only well-characterized examples of strained [1]ferrocenophanes incorporating an element of the second period in the bridge.…”

Section: Summary and Outlook 5077mentioning

confidence: 99%

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

2007

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“…[13±15] The first [1]ferrocenophanes containing Group 16 (S, Se) [16] or Group 13 (B) [17] elements in the bridge were reported very recently. These novel, highly strained species (ring tilts 26 ± 328) also undergo ROP.…”

Section: Introductionmentioning

confidence: 99%

Synthesis, Reactivity, and Ring-Opening Polymerization (ROP) of Tin-Bridged [1]Ferrocenophanes

et al. 1998

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Abstract:The first examples of tinbridged [1]ferrocenophanes, Fe(h-C 5 H 4 ) 2 -SntBu 2 (7a) and Fe(h-C 5 H 4 ) 2 SnMes 2 (7b) have been synthesized by the low-temperature reaction of Fe(h-C 5 H 4 Li) 2´n TME-DA (TMEDA N,N,N',N'-tetramethylethylenediamine) with tBu 2 SnCl 2 and Mes 2 SnCl 2 (Mes 2,4,6-trimethylphenyl), respectively. They were isolated in 65 % (7a) and 85% (7b) yield as orange crystalline solids, which were characterized by multinuclear NMR and UV/Vis spectroscopy, mass spectrometry, elemental analysis, and single-crystal X-ray diffraction. The tilt angles between the planes of the cyclopentadienyl rings are 14.1(2)8 for 7a and 15.2(2)8 (average) for the three independent molecules of 7b in the unit cell. Although they have significantly smaller tilt angles than analogous [1]ferrocenophanes with the lighter Group 14 elements silicon or germanium in the bridge, 7 a and 7 b still readily undergo ring-opening polymerization (ROP) by thermal reaction in the solid state (7 a at 150 8C; 7 b at 180 8C), to give highmolecular-weight poly(ferrocenylstannane)s [Fe(h-C 5 H 4 ) 2 SntBu 2 ] n (8 a) and [Fe(h-C 5 H 4 ) 2 SnMes 2 ] n (8 b). Remarkably, 7 a and 7 b were also found to polymerize in solution at room temperature in the absence of externally added initiators. ROP is much more rapid for 7 a than for 7 b in solution. The cyclic dimers [Fe(h-C 5 H 4 ) 2 SnR 2 ] 2 (3; R tBu, Mes) were formed as by-products in amounts which depended on the solvent. Electrochemical studies of the cyclic dimers and polymers indicated the presence of significant Fe´´´Fe interactions that are mediated by the tin-atom spacer. When benzene solutions of 7 a and 7 b were treated with small amounts of Karstedts catalyst, slower polymerization was observed. Stoichiometric reaction of Pt(1,5-cod) 2 (cod cyclooctadiene) with 7 a yielded the novel trimetallic 1-stanna-2-platina[2]ferrocenophane Fe(h-C 5 H 4 ) 2 Pt(1,5-cod)SntBu 2 (9), which functioned as a sluggish catalyst for the ROP of 7 a and 7 b.

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“…This compound, which was isolated as a dark red oil, exists as a pair of enantiomers resulting from the chiral nature of the silicon center. This effect is reflected particularly in the 13 C NMR spectrum, as 10 separate, closely spaced signals are observed in the Cp region.…”

Section: Resultsmentioning

confidence: 95%

“…[13,18] A possible method for incorporation of boron centers into ferrocene polymers without decrease of solubility was envisaged to be the formation of a poly(ferrocenylsilane)-ferrocenylborane hybrid material. [37] We have previously shown that the addition of hydride-functionalized silanes provides a facile route for molecular weight control in transition metal catalyzed ring-opening polymerizations of sila [1]ferrocenophanes.…”

Section: Resultsmentioning

confidence: 99%

Selective Ring-Opening Reactions of [1]Ferrocenophanes with Boron Halides: A Novel Route to Functionalized Ferrocenylboranes and Boron-Containing Oligo- and Poly(ferrocene)s

et al. 2000

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The reactivity of strained [1]ferrocenophanes, [Fe(eta-C5H4)2ERx] (ERx = SiMe2, 1a: SiMePh, 1b; SnR2, 1c), towards boron halides has been investigated and has been shown to provide a facile pathway to ferrocene derivatives functionalized with Lewis acidic boron centers. The boron halides RBX2 (R = Cl, Ph, fc; X = Cl, Br) (fc = Fe(eta-C5H4)2) lead to selective cleavage of the Si-Cp bonds in 1a and 1b to give, depending on the reaction stoichiometry, functionalized mono- or diferrocenylboranes RnB [(eta-C5H4)Fe(eta-C5H4SiMe2Cl)](3-n) (2a: R = Cl, n = 2; 2b: R = Cl, n = 1; 2c: R = Ph, n = 1) and RnB[(eta-C5H4)Fe(eta-C5H4SiMePhCl)](3-n) (2d: R = Cl, n = 2) in high yields. Compounds 2a-d were characterized by multinuclear NMR spectroscopy, mass spectrometry, and by single-crystal X-ray diffraction (for 2b). Most likely due to steric constraints, a triferrocenylborane was not obtained even from the reaction of BCl3 with an excess of 1a, whereas facile formation of the diferrocenylphenylborane 2c from PhBCl2 and two equivalents of 1a was observed. Selective hydrolysis of the B-Cl bonds of chlorodiferrocenylborane 2b in the presence of trace amounts of water led to the silylated tetranuclear ferrocene complex [(ClMe2Sifc)2B-O-B(fcSiMe2Cl)2] (3) without cleavage of the Si-Cl bonds. The structure of 3 was confirmed by an X-ray diffraction study. Studies of the reactivity of the higher Group 14 homologue of 1a and 1b, the tin-bridged [1]ferrocenophane 1c, revealed that facile addition of B-Cl bonds occurs across the Sn-Cp bonds to yield the 1-stannyl-1'-borylferrocenes [(ClMes2Sn)fc(BClR)] (4a: R = Cl; 4b: R = Ph; Mes = 2,4,6-Me3C6H2). The new synthetic methodology can be extended to bifunctional Lewis acids such as the bis(boryl)ferrocene 1,1'-fc(BBr2)2, which affords the linear boron-bridged ferrocene trimer 1,1'-[fc[B(Br)fcSiMe2Br]2] 5 in 54% isolated yield. In order to incorporate the functionalized ferrocenylboranes into polymer structures, compound 2c was reduced with Li[BEt3H] to give the silicon-hydride functionalized species [PhB[(eta-C5H4)Fe(eta-C5H4SiMe2H)]2] (6), which was then used as a capping reagent in the transition metal catalyzed polymerization of 1a. This process leads to the incorporation of the ferrocenylborane unit into the main chain of a poly(ferrocenylsilane) to afford [PhB-[(fcSiMe2)(n-1)fcSiMe2H]2] (7).

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Incorporation of a First Row Element into the Bridge of a Strained Metallocenophane: Synthesis of a Boron‐Bridged [1]Ferrocenophane

Cited by 114 publications

References 43 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

Synthesis, Reactivity, and Ring-Opening Polymerization (ROP) of Tin-Bridged [1]Ferrocenophanes

Selective Ring-Opening Reactions of [1]Ferrocenophanes with Boron Halides: A Novel Route to Functionalized Ferrocenylboranes and Boron-Containing Oligo- and Poly(ferrocene)s

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