Isolation and characterisation of the mixed-metal alkyl amide [(TMEDA)Na(μ-Bu)(μ-TMP)Mg(TMP)], an unexpected chelate-trapped intermediate in the formation of inverse crowns

Hevia, Eva; Gallagher, Daniel J.; Kennedy, Alan R.; Mulvey, Robert E.; O’Hara, Charles T.; Talmard, Christine

doi:10.1039/b410293b

Cited by 71 publications

(73 citation statements)

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“…In diesem Fall sollte das Monoalkylbisamido-System 75 ([(tmeda)Na(m-Bu)(m-tmp)Mg(tmp)]) in der ersten Stufe eine selektive Monodeprotonierung des Toluols in meta-Position ("5-Position") bewirken. [76,77] Tatsäch Beim Furan findet die AMMM ausschließlich in a-Position statt, was bezüglich der Selektivität nicht weiter überra-schend ist (a-Lithiierungen sind verbreitete Reaktionen). [78] Schon sehr viel ungewöhnlicher ist dagegen die Tatsache, dass die zwölfgliedrige inverse (NaOCMgCO) 2 Umgekehrt vermittelt die AMMM von Dibenzolchrom [79] und Ditoluolchrom [80] zwar nicht die Bildung inverser Kronenverbindungen, bringt aber besondere synergetische Selektivitäten hervor.…”

Section: R E Mulvey Et Alunclassified

Deprotonierende Metallierungen mit 'at‐Verbindungen: Synergie, Synthese und Strukturaufbau

Mongin²,

et al. 2007

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In der organischen Synthesechemie werden Monometallspezies wie Organolithiumverbindungen seit langem für Deprotonierungsreaktionen genutzt. In den letzten Jahren ist mit den 'at‐Komplexen eine neue Klasse von Metallierungsreagentien hinzugetreten, die das Syntheserepertoire metallorganischer Spezies ergänzt. Dank eines frei wählbaren Metallzentrums (Magnesium, Zink oder Aluminium), frei wählbarer Liganden (in Art und Anzahl) und eines frei wählbaren sekundären Metallzentrums (eines Alkalimetalls wie Lithium oder Natrium) sind 'at‐Komplexe äußerst vielseitige basische Reagentien, deren synergetische Reaktionsweisen mit den homometallischen Magnesium‐, Zink‐ oder Aluminiumverbindungen nicht beobachtet werden. Deprotonierungen mit metallorganischen 'at‐Komplexen haben neue Perspektiven in der organischen Chemie eröffnet, mit ungewöhnlichen Reaktivitäten und manchmal unvorhergesehenen Regioselektivitäten.

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Section: R E Mulvey Et Alunclassified

Deprotonierende Metallierungen mit 'at‐Verbindungen: Synergie, Synthese und Strukturaufbau

Mongin²,

et al. 2007

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“…Zincate 3 has been characterised by X-ray crystallography in the solid state and by NMR spectroscopy in deuterated THF solution. Keywords: alkali metals · metallation · synergic chemistry · zincates piperidide) monometallates benzene at room temperature, [9] whereas its even more reactive unsolvated form 2 ]" can selectively double deprotonate benzene at the sterically optimum 1,4-positions. [10] Another example that illustrates the selectivity of these mixed-metal reagents is the stoichiometric controlled deprotonation of naphthalene with the TMP-dialkyl zincate [(tmeda)NaA C H T U N G T R E N N U N G (tBu)-…”

Section: A C H T U N G T R E N N U N G (Tmp)zna C H T U N G T R E N Nmentioning

confidence: 99%

“…Crystal data for 3: C 27 H 57 N 4 NaZn; monoclinic space group P2 1 , a = 9.2211(3) b = 18.3639(6) c = 9.4349(3) , b = 94.172(2)8, V = 1593.43 (9) 3 , T = 123 K, Z = 2, 1 calcd = 1.097 Mg m À3 , 2q max = 54.168. R1 = 0.0405 (for 5033 reflections with I > 2s(I)) wR2 = 0.0690 and S = 1.054 for 351 parameters and 6016 unique reflections.…”

mentioning

confidence: 99%

Synthetic and Structural Insights into the Zincation of Toluene: Direct Synergic Ring Metallation versus Indirect Nonsynergic Lateral Metallation

Armstrong

García‐Álvarez

Graham

et al. 2009

Chemistry A European J

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Unprecedented direct zincation of toluene can be achieved by using a bimetallic base that bypasses the acidic methyl group and instead affords a statistical mixture of the meta and para deprotonated regioisomers (see scheme).magnified imageToluene has been directly zincated by reaction with the heteroleptic sodium zincate [(tmeda)Na(tBu)(tmp)Zn(tBu)] (1) to afford a statistical mixture of the meta and para regioisomers of [(tmeda)Na(C6H4Me)(tmp)Zn(tBu)] (2) (TMEDA=N,N,N′,N′‐tetramethylethylenediamine, TMP=2,2,6,6‐tetramethylpiperidide). Interestingly, the methyl group of toluene has been left untouched by the mixed‐metal base. The crystal structures of both regioisomers have been elucidated by using X‐ray crystallography, which revealed a common motif, in which zinc lies in the same plane as the tolyl ring and binds strongly to the carbon that has experienced the deprotonation, leading to a covalent σ bond; whereas sodium adopts a perpendicular disposition, π‐engaging with the aromatic ring. DFT studies of the reaction of 1 with toluene showed that of the four possible regioisomers, the experimentally observed meta and para ones are the most thermodynamically preferred products due to a large extent to the combined (synergic) effect of the zinc and sodium and the different way in which each metal binds to the tolyl anion. In contrast, the more straightforward benzyl‐based zincate [(tmeda)2Na(CH2Ph)Zn(tBu)2] (3) is obtained through an indirect route, in which toluene is first laterally metallated by monometallic butylsodium to afford benzylsodium, which then forms a mixed‐metal compound by co‐complexation with tBu2Zn. Zincate 3 has been characterised by X‐ray crystallography in the solid state and by NMR spectroscopy in deuterated THF solution.

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“…b) Section of the extended framework structure showing atom connectivity between normal-C2 (C1 and C28) sites to K, and abnormal-C4 (C2 and C29) and the nBu ligand to Mg. Sodium magnesiate [(TMEDA)NaMg(TMP)2(nBu)] [24] 4 reacted with IPr in a 1:1 stoichiometry in n-hexane and after a crystallisation process in n-hexane/THF produced the tris(monoanionic) carbene [(THF)3Na(-IPr -)Mg(THF)(IPr Figure 2). Our NMR studies point to a complicated ligand redistribution process in forming 5 (Scheme 2) when THF is present in the reaction media.…”

mentioning

confidence: 99%

“…Complexes of type [(donor)NaMg(TMP)2(nBu)] are common. [24] Pre-inverse-crowns invariably magnesiate via nBu basicity so part of the template attached to "C2" through Na could execute the para-aryl magnesiation. [27] However, given the extended length of emergent IPr -with respect to substituted benzene substrates, this magnesiation is likely to be accompanied by template fragmentation as its 12-atom ring would be too small to circumnavigate IPr -.…”

mentioning

confidence: 99%

Alkali‐Metal‐Mediated Magnesiations of an N‐Heterocyclic Carbene: Normal, Abnormal, and “Paranormal” Reactivity in a Single Tritopic Molecule

et al. 2015

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This version is available at https://strathprints.strath.ac.uk/54271/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge.Any correspondence concerning this service should be sent to the Strathprints administrator: strathprints@strath.ac.ukThe Strathprints institutional repository (https://strathprints.strath.ac.uk) is a digital archive of University of Strathclyde research outputs. It has been developed to disseminate open access research outputs, expose data about those outputs, and enable the management and persistent access to Strathclyde's intellectual output. O'HaraAbstract: The metalation reaction is currently in the midst of an extraordinary transformative period due largely to development of bimetallic metalating agents, which operate through metal-metal' synergistic effects inaccessible to unimetal bases. Here the sodium alkylmagnesium amide [Na4Mg2(TMP)6(nBu)2], a template base as its deprotonating action is dictated primarily by its 12-atom ring structure, is studied with the common NHC, IPr [1,3-bis(2,6-diisopropylphenyl)-imidazol-2-ylidene]. Remarkably, magnesiation of IPr occurs at the para-position of an aryl substituent, sodiation occurs at the abnormal C4 position and a dative bond occurs between normal C2 and sodium, all within a 20-atom ring structure that accommodates two IPr 2-dianions. Studies with different K-Mg and Na-Mg bimetallic bases have realized two other magnesiated NHC structures containing two or three IPr -monoanions bound to

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Isolation and characterisation of the mixed-metal alkyl amide [(TMEDA)Na(μ-Bu)(μ-TMP)Mg(TMP)], an unexpected chelate-trapped intermediate in the formation of inverse crowns

Abstract: Only two-fold amination occurs when 3 molar equivalents of TMPH are offered to a 1:1 BuNa-Bu2Mg mixture; adding TMEDA gives the mixed alkyl amide [(TMEDA)Na(mu-Bu)(mu-TMP)Mg(TMP)], which itself affords the phenyl-bridged analogue when reacted with benzene.

Cited by 71 publications

References 5 publications

Deprotonierende Metallierungen mit 'at‐Verbindungen: Synergie, Synthese und Strukturaufbau

Deprotonierende Metallierungen mit 'at‐Verbindungen: Synergie, Synthese und Strukturaufbau

Synthetic and Structural Insights into the Zincation of Toluene: Direct Synergic Ring Metallation versus Indirect Nonsynergic Lateral Metallation

Alkali‐Metal‐Mediated Magnesiations of an N‐Heterocyclic Carbene: Normal, Abnormal, and “Paranormal” Reactivity in a Single Tritopic Molecule

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