Group 4 Metallocene Complexes and Cyanopyridines: Coordination or Coupling to Metallacycles

Tomaschun, Gabriele; Altenburger, Kai; Reiß, Fabian; Becker, Lisanne; Spannenberg, Anke; Arndt, Perdita; Jiao, Haijun; Rosenthal, Uwe

doi:10.1002/ejic.201501235

Cited by 21 publications

(39 citation statements)

References 51 publications

(26 reference statements)

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“…This supports spontaneously C-C coupling reactions of 1,3-or 1,4dicyanobenzene, [12] adiponitrile, [12] 2,6-dicyanopyridine [13] or pyrazine [9,14] without or of quinoxalines [15] with C-H bond activation reactions and enable for instance the formation of the trinuclear complexes IV and V (Scheme 2). This supports spontaneously C-C coupling reactions of 1,3-or 1,4dicyanobenzene, [12] adiponitrile, [12] 2,6-dicyanopyridine [13] or pyrazine [9,14] without or of quinoxalines [15] with C-H bond activation reactions and enable for instance the formation of the trinuclear complexes IV and V (Scheme 2).…”

Section: Introductionsupporting

confidence: 70%

“…Here, the increased steric demand hinders the formation of rectangles or squares. The Ti-N and Zr-N distances of the triangles 16-19 are on average slightly longer (2.28-2.37 Å) than in the tetramers (10)(11)(12)(13)(14)(15). Table 3 shows the distances between the metal centers, the angles between the metal centers und the bridging ligands, and the angles between the metal centers and their sum for the complexes 16-19.…”

Section: Resultsmentioning

confidence: 99%

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Self‐Assembly Reactions To Form Multinuclear Zirconium(III) and Titanium(III) Complexes with Imidazole Derivatives as Bridging Ligands

et al. 2018

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Self-assembly reactions with low valent early transition metals, leading to neutral multinuclear complexes are rare. Mostly late transition metals like Pt, Pd or Ru together with Nheterocycles or O-donor-based ligands are used to form supramolecular coordination complexes. This paper reports on selfassembly reactions of low valent titanocene and zirconocene units and five-membered N-heterocycles as bridging ligands. These reactions lead to novel molecular triangles and rectangles with the metal centers marking the vertices. Five different imidazole derivatives and four different metallocene precursors were used. For the first time, molecular triangles and architec-Scheme 1. Molecular quadrangle with pyrazine I and 4,4′-bipyridine II and a combination of both III as bridging ligands.[a]

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Section: Introductionsupporting

confidence: 70%

Section: Resultsmentioning

confidence: 99%

Self‐Assembly Reactions To Form Multinuclear Zirconium(III) and Titanium(III) Complexes with Imidazole Derivatives as Bridging Ligands

et al. 2018

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“…Instead of the coordination of the substrate, we examined C−C couplings in the reaction of 2‐(trimethylsilylethynyl)pyridine ( tmsepy ) with [Cp 2 Ti( η 2 ‐Me 3 SiC 2 SiMe 3 )] (Scheme , left), resulting in two regioisomeric titanacyclopentadienes . A similar C−C coupling was observed upon addition of 2‐cyanopyridine ( cypy ) to [Cp* 2 M( η 2 ‐Me 3 SiC 2 SiMe 3 )] (M=Ti, Zr; Cp*= η 5 ‐pentamethylcyclopentadienyl) …”

Section: Introductionmentioning

confidence: 99%

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

Reiß

Altenburger

Becker

et al. 2016

Chemistry A European J

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Reactions of group 4 metallocene sources with 2-substituted pyridines were investigated to evaluate their coordination type between innocent and reductive dearomatisation as well as to probe the possibility for couplings. A dependence on the cyclopentadienyl ligands (Cp, Cp*), the metals (Ti, Zr), and the substrates (2-phenyl-, 2-acetyl-, and 2-iminopyridine) was observed. While 2-phenylpyridine is barely reactive, 2-acetylpyridine reacts vigorously with the Cp-substituted complexes and selectively with their Cp* analogues. With 2-iminopyridine, in all cases selective reactions were observed. In the isolated [Cp Ti], [Cp Zr], and [Cp* Zr] compounds the substrate coordinates by its pyridyl ring and the unsaturated side-chain. Subsequently, the pyridine was dearomatised, which is most pronounced in the [Cp* Zr] compounds. Using [Cp* Ti] leads to the unexpected paramagnetic complexes [Cp* Ti (N,O-acpy)] and [Cp* Ti (N,N'-impy)]. This highlights the non-innocent character of the pyridyl substrates.

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“…Such coupling reactions were later described for 2,6‐dicyanopyridine and very recently by Reiß, Beweries and coworkers for 2‐cyanofuran as well as 2‐cyanothiophene, giving several mixed tri‐ and tetranuclear complexes by homo‐ and heterocoupling using Cp* 2 M(η 2 ‐btmsa) (M=Ti, Zr) . When changing from aryl‐dinitriles to dicyanoalkyl adiponitrile, by a nitrile‐nitrile C−C coupling and subsequent protonation no 1‐titana‐2,5‐diaza‐cyclopenta‐2,4‐diene but a 1,4‐diazadiene complex was formed in a yield of 46 % (Scheme )…”

Section: Examples For Substrate Substitutionmentioning

confidence: 93%

Advantages of Group 4 Metallocene Bis(trimethylsilyl)acetylene Complexes as Metallocene Sources Towards Other Synthetically used Systems

Rosenthal

2019

ChemistryOpen

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Active species for synthetic and catalytic applications are formed from well defined complexes or mixtures of compounds. For group 4 metallocenes, three pathways for the formation of the reactive complex fragment [Cp′ 2 M] are known: (i) reductive mixtures and well defined complexes which are able to form the metallocene fragments either by (ii) addition or (iii) substitution reactions. In this account for each of theses systems (i)–(iii) a prominent example will be discussed in detail, (i) the Negishi reagent Cp 2 ZrCl 2 /n‐BuLi, (ii) bis(η 5 : η 1 ‐pentafulvene) complexes and (iii) metallocene bis(trimethylsilyl)acetylene complexes, to show the advantages and the disadvantages for each of these methods for synthetic applications. This account summarizes some main advantages of group 4 metallocene bis(trimethylsilyl)acetylene complexes as metallocene generating agents over other synthetically used systems. For each of the special purposes, all described systems have advantages as well as disadvantages. The aim of this overview is to help synthetic chemists in selecting the most effective system on the basis of [Cp′ 2 M] (M=Ti, Zr) for synthetic or catalytic puposes.

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Group 4 Metallocene Complexes and Cyanopyridines: Coordination or Coupling to Metallacycles

Cited by 21 publications

References 51 publications

Self‐Assembly Reactions To Form Multinuclear Zirconium(III) and Titanium(III) Complexes with Imidazole Derivatives as Bridging Ligands

Self‐Assembly Reactions To Form Multinuclear Zirconium(III) and Titanium(III) Complexes with Imidazole Derivatives as Bridging Ligands

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

Advantages of Group 4 Metallocene Bis(trimethylsilyl)acetylene Complexes as Metallocene Sources Towards Other Synthetically used Systems

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