Heavy Grignard Reagents: Challenges and Possibilities of Aryl Alkaline Earth Metal Compounds

Westerhausen, Matthias; Gärtner, Martin; Fischer, R.; Langer, Jens; Yu, Lian; Reiher, Markus

doi:10.1002/chem.200700558

Cited by 164 publications

(85 citation statements)

References 131 publications

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“…The chemistry is simplified by the absence of Ca 2 + redox chemistry. [19][20][21][22][23][24] Treatmento fy tterbium with iodobenzene in thf yields ar ed solution described as "PhYbI"(thf) x . [25] Although written as containing divalent ytterbium, the mixture contains trivalents pecies, as proposedb yE vanse tal.…”

Section: Introductionmentioning

confidence: 99%

Lanthanoid Pseudo‐Grignard Reagents: A Major Untapped Resource

Ali

Deacon

Junk

et al. 2017

Chemistry A European J

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Pseudo-Grignardr eagents PhLnI (Ln = Yb, Eu), readily prepared by the oxidative addition of iodobenzene to ytterbium or europium metal at À78 8Cint etrahydrofuran (THF) or 1,2-dimethoxyethane (DME), react with ar ange of bulky N,N'-bis(aryl)formamidines to generate an extensive series of Ln II or more rarely Ln III complexes,n amely [Eu(Dipp-, and [Yb(XylForm) 2 I(dme)]·dme (7b){ (Form = ArNCHNAr;X ylForm (Ar = 2,6-Me 2 C 6 H 3 ), MesForm (Ar = 2,4,6-Me 3 C 6 H 2 ), DippForm (Ar = 2,6-iPr 2 C 6 H 3 )}. Reaction of PhEuI and MesFormH in DME consistently gave 2, and reactionw ith XylFormH in THF gave 4.E uropium complexes 1 and 3a are seven-coordinate divalent monomers, whilst 3b is as even-coordinate dme-bridged polymer.C omplex 5a of the smaller Yb II is as ix-coordinate monomer,b ut the related 6 and 7a are six-coordinatei odide-bridged dimers. 4 is at rivalent seven-coordinate hydroxide-bridged dimer,w hereas complexes 5b and 7b are seven-coordinate monomeric Yb III derivatives. Ac haracteristic structural feature is that iodide ligands are cisoid to the formamidinate ligand.T oi llustrate the synthetic scope of the pseudoGrignardr eagents,[ Yb(Ph 2 pz)I(thf) 4 ]( Ph 2 pz = 3,5-diphenylpyrazolate) was oxidised with 1,2-diiodoethane to afford seven-coordinate monomeric pyrazolato-ytterbium (III)

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Section: Introductionmentioning

confidence: 99%

Lanthanoid Pseudo‐Grignard Reagents: A Major Untapped Resource

Ali

Deacon

Junk

et al. 2017

Chemistry A European J

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“…Over the past few decades, the understanding of the coordination chemistry of the elements of the heavy alkaline earth metals (M = Ca, Sr, Ba) has advanced dramatically, owing primarily to an interest in their application as chemical vapour deposition precursors (Hanusa 1990(Hanusa , 1993(Hanusa , 2000(Hanusa , 2002Westerhausen 1998Westerhausen , 2001Westerhausen , 2006Westerhausen , 2008Alexander & Ruhlandt-Senge 2002;Westerhausen et al 2007). Reaction studies upon organometallic compounds of calcium, strontium and barium have, however, been largely overshadowed by those of the lighter congener, magnesium.…”

Section: Introductionmentioning

confidence: 99%

Heterofunctionalization catalysis with organometallic complexes of calcium, strontium and barium

et al. 2010

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Despite the routine employment of Grignard reagents and Hauser bases as stoichiometric carbanion reagents in organic and inorganic synthesis, a defined reaction chemistry encompassing the heavier elements of Group II (M = Ca, Sr and Ba) has, until recently, remained unreported. This article provides details of the recent progress in heavier Group II catalysed small molecule transformations mediated by well-defined heteroleptic and homoleptic complexes of the form LMX or MX 2 ; where L is a mono-anionic ligand and X is a reactive s-bonded substituent. The intra-and intermolecular heterofunctionalization (hydroamination, hydrophosphination, hydrosilylation and hydrogenation) of alkenes, alkynes, dienes, carbodiimides, isocyanates and ketones is discussed.

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“…Considerable skill was required to isolate the compounds at low temperatures and to obtain crystals for X-ray studies. [13] The greater stability of 2,4,6-triphenylphenyl derivatives, however, suggested that the nucleophilicity of the carbanion could be sufficiently reduced by delocalization to prevent attack on the solvent. The reaction of 1-bromo-2,4,6-triphenylbenzene with activated magnesium in the traditional way yielded the Grignard reagent 5 (Scheme 3) as colorless needles.…”

Section: Theorganometallicchemistryofthes-blockelements-frommentioning

confidence: 98%

“…[13,14] The Ca I derivative 6, which contains no CaÀCa bonds, represents a further important step in the study of this unusual oxidation state.…”

Section: Theorganometallicchemistryofthes-blockelements-frommentioning

confidence: 99%

Organometallic Compounds of the Heavier s‐Block Elements—What Next?

Smith

2009

Angew Chem Int Ed

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alkali metals · alkaline earth metals · coordination modes · methandiides · organometallic compoundsTheorganometallicchemistryofthes-blockelements-from its origins 150 years ago to the present day-was recently reviewed in two fascinating essays. [1,2] Organolithium and Grignard reagents, now often bought in solution, have been used routinely in organic syntheses for many years. In contrast, much less is known about the potential, in synthesis or catalysis, of organometallic compounds of the heavier sblock elements. In part, this neglect is a natural consequence of the attention paid to compounds of the lighter elements, but development has also been held back by the simplistic view given in some textbooks that, whereas LiÀC and MgÀC bonds are covalent, KÀC and CaÀC bonds are ionic. The carbanions associated with the metal cations are, therefore, powerful nucleophiles that deprotonate ether solvents. This has made synthesis difficult and discouraged investigation.The applications of organolithium and Grignard-type reagents have been greatly expanded by the development of so-called "superbases", that is, compounds containing two different metals, [2,3] but what of the organometallic compounds of individual heavier s-block elements in the absence of lighter atoms? A variety of alkali-metal compounds have been known for some time, [4] but it is only recently that researchers have made significant progress in exploring the chemistry of the organometallic compounds of the heavier alkaline earth metals.[5] As in organolithium compounds, [6] the bonding in all these compounds is highly ionic, but when the nucleophilicity of the carbanion is reduced by extensive delocalization of the negative charge on to bulky aryl, bdiketiminato or silicon-containing ligands, a range of compounds can be isolated. It is clear that these do not simply provide a minor variation on what is already known about the lighter elements. Unexpected reactions and unprecedented structures point to exciting new chemistry. This article highlights examples from two of the leading research groups in this area. [7,8] In each case, the compounds of the heavier elements differ from those of the lighter congeners, and show how changes in the size of the metals determine the structures of their organometallic compounds.The synthetic potential of methandiides (R 2 CM 2 ) has long been recognized, [9] but few have been isolated. The dimeric compounds [{[Ph 2 P(NSiMe 3 )] 2 C} 2 M 4 ] (M = Li, 1; Scheme 1), were obtained by the research groups of Cavell [10] and Stephan [11] 10 years ago. Further dimers in which M

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Heavy Grignard Reagents: Challenges and Possibilities of Aryl Alkaline Earth Metal Compounds

Cited by 164 publications

References 131 publications

Lanthanoid Pseudo‐Grignard Reagents: A Major Untapped Resource

Lanthanoid Pseudo‐Grignard Reagents: A Major Untapped Resource

Heterofunctionalization catalysis with organometallic complexes of calcium, strontium and barium

Organometallic Compounds of the Heavier s‐Block Elements—What Next?

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