Reactions of 2‐Substituted Pyridines with Titanocenes and Zirconocenes: Coupling versus Dearomatisation

Reiß, Fabian; Altenburger, Kai; Becker, Lisanne; Schubert, Kathleen; Jiao, Haijun; Spannenberg, Anke; Hollmann, Dirk; Arndt, Perdita; Rosenthal, Uwe

doi:10.1002/chem.201504411

Cited by 15 publications

(16 citation statements)

References 64 publications

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“…The reactions of Cp* 2 M(η 2 ‐btmsa) with 2‐acetylpyridine gave with substitution of the alkyne a Ti(III) or a Zr(IV) complex (Scheme ) …”

Section: Reactions With Neutral N‐donor Compoundsmentioning

confidence: 83%

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Recent Synthetic and Catalytic Applications of Group 4 Metallocene Bis(trimethylsilyl)acetylene Complexes

Rosenthal

2019

Eur J Inorg Chem

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With the 30 years old first example of a stable group 4 metallocene bis(trimethylsilyl)acetylene (btmsa) complex Cp2Ti(η2‐btmsa) a series of similar complexes like Cp′2M(η2‐btmsa) (M = Ti, Zr; Cp′ = Cp, Cp* as η5‐pentamethylcyclopentadienyl and Cp′2 = rac‐(ebthi) as rac‐1,2‐ethylene‐1,1′‐bis(η5‐tetrahydroindenyl) ) represent excellent sources for the generation of the very reactive coordinatively and electronically unsaturated complex fragments [Cp'2M], which were used in many synthetic and catalytic reactions. Examples for this were oresented in several papers and summarized in some reviews. In this update new reactions of group 4 metallocene bis(trimethylsilyl)acetylene complexes towards symmetrically and unsymmetrically α‐dihetero‐substituted alkynes, reactions with other alkynes, di‐ and polyynes to metallacyclopentadienes as well as the conversions of the formed products are summarized. Additionally, novel synthetic applications of the formed metallacyclopentadienes on the basis of the zirconocene bis(trimethylsilyl)acetylene complex Cp2Zr(py)(η2‐btmsa) are highlighted. Reactions with imines, neutral N‐donor ligands, E‐H compounds (E = N, O, P), molecular hydrogen, water, phosphino‐ and aminoboranes, E‐Cl compounds (E = C, P), disilylated germylenes and aryloxy ketones were described. Different self‐assembly reactions to multinuclear complexes by using group 4 metallocene bis(trimethylsilyl)acetylene complexes in C‐C coupling reactions with or without C‐H bond activation to tri‐ or tetranuclear complexes are considered, too. These examples are discussed following the general L‐M‐S principle for stoichiometric and catalytic reactions, whereby different ligands L (L = Cp′ = Cp, Cp*, rac‐ebthi), metals M (M = Ti, Zr, Hf) and substrate substituents S influence the reactivity and the obtained products.

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“…The reactions of Cp* 2 M(η 2 ‐btmsa) with 2‐acetylpyridine gave with substitution of the alkyne a Ti(III) or a Zr(IV) complex (Scheme ) …”

Section: Reactions With Neutral N‐donor Compoundsmentioning

confidence: 83%

“…In the above described reaction of Cp 2 Ti(η 2 ‐btmsa) with PhN=C( p Tol)‐ p Tol an azabutadiene complex was formed (Scheme ) . In the case of 2‐phenylpyridine neither ortho ‐metallated nor dearomatised products were obtained in reactions with different complexes Cp′ 2 M(L)(η 2 ‐btmsa) …”

Section: Reactions With Neutral N‐donor Compoundsmentioning

confidence: 99%

Recent Synthetic and Catalytic Applications of Group 4 Metallocene Bis(trimethylsilyl)acetylene Complexes

Rosenthal

2019

Eur J Inorg Chem

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“…Pyridine dearomatization in the presence of Group IV transition metals is unprecedented, except for reactions that involve redox‐active ligands in the presence of selected metallocenes (Figure ; I ) . However, organolanthanide complexes are well known to undergo intramolecular metal‐to‐ligand alkyl migrations that cause pyridine dearomatization (Figure ; II ), which include deeper and unpredictable ligand rearrangements .…”

Section: Resultsmentioning

confidence: 99%

Benzoimidazole‐Pyridylamido Zirconium and Hafnium Alkyl Complexes as Homogeneous Catalysts for Tandem Carbon Dioxide Hydrosilylation to Methane

et al. 2018

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Neutral ZrIV and HfIV alkyl/amido complexes stabilized by a tridentate N ligand that contains a “rolling” heterodentate benzoimidazole fragment have been prepared and characterized. The ultimate nature of the ligand denticity, the electronic properties of the ligand binding pocket and the metal coordination environment are controlled by the protection/deprotection of the benzoimidazole NH group. The metal precursor used [MIV(Bn)4 or MIV(NMe2)4] also has an influence on the final coordination sphere of the complex; indeed, a permanent central pyridine dearomatization occurs in the presence of dimethylamido ancillary groups. DFT calculations on the real system have been used to elucidate the mechanism. Selected alkyl species from this series have been scrutinized for the tandem hydrosilylation of CO2 to CH4 in combination with the strong Lewis acid B(C6F5)3 using a variety of hydrosilanes. A positive effect of the hardness modification of the ligand donor atom set is observed in the catalytic outcomes. Indeed, κ3{N−,N,N−}ZrIV(Bn)2 catalyzes the process to methane selectively with a turnover frequency as high as 272 h−1 (at 96 % substrate conversion) almost twice as much as that claimed for the benchmark κ3{O−,O,O−}ZrIV(Bn)2 complex under similar experimental conditions.

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“…Furthermore, the split‐off of [Cp* 2 M] is more probable to result in stable organic substances. Besides, the compounds contain vacant coordination sites with the N atoms of the pyridine ring, which might lead to fascinating new complexes . Owing to this, the investigation of the reactivity of the pyridyl‐substituted compounds is of considerable interest.…”

Section: Introductionmentioning

confidence: 99%

Reactivity Study of Pyridyl‐Substituted 1‐Metalla‐2,5‐diaza‐cyclopenta‐2,4‐dienes of Group 4 Metallocenes

Becker

Reiß

Altenburger

et al. 2016

Chemistry A European J

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In this work the reactivity of 1-metalla-2,5-diaza-cyclopenta-2,4-dienes of group 4 metallocenes, especially of the pyridyl-substituted examples, towards small molecules is investigated. The addition of H2 , CO2 , Ph-C≡N, 2-py-C≡N, 1,3-dicyanobenzene or 2,6-dicyanopyridine results in exchange reactions, which are accompanied by the elimination of a nitrile. For CO2 , a coordination to the five-membered cycle occurs in case of Cp*2 Zr(N=C(2-py)-C(2-py)=N). A 1,4-diaza-buta-1,3-diene complex is formed by H-transfer in the conversion of the analogous titanocene compound with CH3 -C≡N, PhCH2 -C≡N or acetone. For CH3 -C≡N a coupling product of three acetonitrile molecules is established additionally. In order to split off the metallocene from the coupled nitriles, we examined reactions with HCl, PhPCl2 , PhPSCl2 and SOCl2 . In the last case, the respective thiadiazole oxides and the metallocene dichlorides were obtained. A subsequent reaction produced thiadiazoles.

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Reactions of 2‐Substituted Pyridines with Titanocenes and Zirconocenes: Coupling versus Dearomatisation

Cited by 15 publications

References 64 publications

Recent Synthetic and Catalytic Applications of Group 4 Metallocene Bis(trimethylsilyl)acetylene Complexes

Recent Synthetic and Catalytic Applications of Group 4 Metallocene Bis(trimethylsilyl)acetylene Complexes

Benzoimidazole‐Pyridylamido Zirconium and Hafnium Alkyl Complexes as Homogeneous Catalysts for Tandem Carbon Dioxide Hydrosilylation to Methane

Reactivity Study of Pyridyl‐Substituted 1‐Metalla‐2,5‐diaza‐cyclopenta‐2,4‐dienes of Group 4 Metallocenes

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