Stabile Cyclopentine – Metalle machen's möglich!?

Rosenthal, Uwe

doi:10.1002/ange.200401761

Cited by 58 publications

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“…[13] Thus,t he metallacyclobutadiene unit in 2 is compressed along the C7-C9 direction, leading to the disappearance of the bonding interaction between Os1 and C8, in sharp contrast to the previous report of 1,3-related metal-carbon bonding. [7,15] Complex 2 was further characterized by NMR spectroscopy,h igh-resolution mass spectrometry (HRMS), and elemental analysis.I nt he 1 HNMR spectrum, the doublet resonance signal at d = 14.00 ppm is assigned to the OsCH proton, which falls within the range of signals of OsCH protons in reported osmapentalynes and osmapentalenes (d = 13.25-14.25 ppm). Accordingly,compound 2 contains ametallapentalene unit and am etallacyclobutadiene unit, which can be considered as arare example of ametallacyclobutadiene with al ate transition metal.…”

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confidence: 99%

Stabilizing Two Classical Antiaromatic Frameworks: Demonstration of Photoacoustic Imaging and the Photothermal Effect in Metalla‐aromatics

et al. 2015

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Stabilizing Two Classical Antiaromatic Frameworks: Demonstration of Photoacoustic Imaging and the Photothermal Effect in Metalla‐aromatics

et al. 2015

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“…Therefore,w eh ave successfully stabilized two classical antiaromatic systems by using one metal fragment at ambient temperature.T his result demonstrates the ability of ametal fragment to stabilize antiaromatic and/or strained systems. [7,15] Complex 2 was further characterized by NMR spectroscopy,h igh-resolution mass spectrometry (HRMS), and elemental analysis.I nt he 1 HNMR spectrum, the doublet resonance signal at d = 14.00 ppm is assigned to the OsCH proton, which falls within the range of signals of OsCH protons in reported osmapentalynes and osmapentalenes (d = 13.25-14.25 ppm). [7,8] Theo ther three proton signals on the metallacycle are detected in the aromatic regions (H3:8 .54, H5:8.78, and H8:8.20 ppm).…”

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Stabilizing Two Classical Antiaromatic Frameworks: Demonstration of Photoacoustic Imaging and the Photothermal Effect in Metalla‐aromatics

et al. 2015

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Antiaromatic species are substantially less thermodynamically stable than aromatic moieties. Herein, we report the stabilization of two classical antiaromatic frameworks, cyclobutadiene and pentalene, by introducing one metal fragment through the first [2+2] cycloaddition reaction of a latetransition-metal carbyne with alkynes. Experimental observations and theoretical calculations reveal that the metal fragment decreases the antiaromaticity in cyclobutadiene and pentalene simultaneously, leading to air-and moisture-stable products. These molecules show broad absorption from the UV to the near-IR region, resulting in photoacoustic and photothermal effects for metalla-aromatic compounds for the first time. These results will encourage further efforts into the exploration of organometallic compounds for photoacoustic-imagingguided photothermal therapy.Aromaticity, an old but still fascinating topic in organic chemistry, has attracted continuous attention from both experimental and theoretical chemists for many decades. [1] According to the Hückel aromaticity rule, [2] cyclic species with 4n + 2 p electrons are aromatic and thus more stable than antiaromatic moieties that contain 4n p electrons. For instance, cyclobutadiene (CBD; Scheme 1, compound I) and pentalene (Scheme 1, compound II), two typical representatives of antiaromatic compounds for monocyclic and bicyclic systems, are highly unstable. [3,4] CBD, with four p electrons, is highly reactive and antiaromatic and was first captured in 1965.[3] Thereafter, the antiaromaticity and geometry of CBD have continued to intrigue computational and synthetic chemists.[5] Pentalene, the archetypal antiaromatic compound with eight p electrons, is highly unstable and was first observed in 1997 in argon matrices. [4, 6] Thus, efforts have been made to stabilize these antiaromatic species. Among various stabilizing approaches, introducing a metal fragment into the carbocycle has been an effective strategy. [7][8][9][10] A series of metallapentalenes [8, 9] and metallacyclobutadienes [10] have been realized through this strategy. However, the simultaneous stabilization of two antiaromatic systems by one metal fragment has not been reported to date. Herein, we report the stabilization of two typically antiaromatic frameworks, CBD and pentalene, by introducing a metal fragment (III in Scheme 1) through unprecedented [2+2] cycloaddition reactions of alkynes with a late-transition-metal carbyne complex. These novel metallaaromatics exhibit broad absorption and remarkable photoacoustic and photothermal properties.The treatment of osmapentalyne 1 [7] with HC CCOOH or HCCOEt in dichloromethane at room temperature afforded complexes 2 or 3, respectively (Scheme 2), which are air and moisture stable. Specifically, both of them can be stored in air at room temperature for several weeks in the solid state. The driving force for the formal [2+2] cycloaddition reaction of osmapentalyne 1 with the alkynes could be attributed to the release of the large ring strain in the fiv...

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“…Nevertheless, some very view examples exist in which the substitution of the bis(trimethylsilyl)acetylene ligand did not work and a coupling of the alkyne with other substrates was found. [2][3][4][5][6][7][8][9][10][11][12][13][14]17,22] The main advantages of one complex of this group, Cp 2 Zr (py)(η 2 -btmsa) compared to other [Cp 2 Zr] generating systems, were summarized by Tilley et al and discussed below in detail. All these advantages are not only restricted to the zirconium complex Cp 2 Zr(pyr)(η 2 -btmsa) but were described in a similar manner for other group 4 metallocene bis(trimethylsilyl) acetylene complexes for several synthetic and catalytic reactions.…”

Section: Metallocene Complexes With Bis(trimethylsilyl)acetylene Cp' mentioning

confidence: 99%

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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Stabile Cyclopentine – Metalle machen's möglich!?

Cited by 58 publications

References 60 publications

Stabilizing Two Classical Antiaromatic Frameworks: Demonstration of Photoacoustic Imaging and the Photothermal Effect in Metalla‐aromatics

Stabilizing Two Classical Antiaromatic Frameworks: Demonstration of Photoacoustic Imaging and the Photothermal Effect in Metalla‐aromatics

Stabilizing Two Classical Antiaromatic Frameworks: Demonstration of Photoacoustic Imaging and the Photothermal Effect in Metalla‐aromatics

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

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