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Zhong, Zhiyuan; Schneiderbauer, Stefan; Dijkstra, Pieter J.; Westerhausen, Matthias; Feijén, Jan

doi:10.1023/a:1016092420618

Cited by 53 publications

(40 citation statements)

References 22 publications

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“…Due to the non-toxicity of calcium, many of these organocalcium compounds could serve as highly sought polymerization initiators for example, in ring opening polymerization of cyclic esters. Investigations towards this use were performed by many research groups [19,77,78] and are summarized in recent reviews. [79] The low reactivity of the calcium metal towards 1,4-diiodobenzene yielded only the mono-insertion product [I-C 6 H 4 -CaIA C H T U N G T R E N N U N G (thf) 4 ] even in the presence of excess of calcium powder, whereas diiodobenzene is able to react twice with magnesium shavings [41] or lithium reagents.…”

Section: Prospectsmentioning

confidence: 99%

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

Westerhausen

Gärtner

Fischer

et al. 2007

Chemistry A European J

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164

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Compounds of the type aryl--M--X, with M=Ca, Sr, Ba and X as any kind of ligand (such as halide, phosphanide, amide, aryl), are presented. The low reactivity of the heavy alkaline earth metals calcium, strontium, and barium enforces an activation prior to use for the direct synthesis. The insertion of these metals into C--I bonds of aryl iodides (direct synthesis) yields aryl metal iodides and has to be performed at low temperatures and in THF. Aryl alkaline-earth-metal compounds show some characteristics: 1) the ease of ether cleavage enforces low reaction temperatures, 2) for Sr and Ba the Schlenk equilibrium is shifted towards homoleptic MI2 and MPh2, 3) high solubility of diaryl alkaline-earth-metal derivatives in THF even at low temperatures initiated quantum chemical investigations on the aggregation behavior, and 4) a strong low field shift of the 13C resonances of the ipso carbon atoms in NMR spectra was observed. First results from quantum chemical calculations on diaryl dicalcium(I) suggest a long Ca--Ca bond with a considerable Ca--Ca bond dissociation energy. Initial results on a selection of applications such as metallation, metathesis, and addition reactions of aryl calcium compounds are presented as well.

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Section: Prospectsmentioning

confidence: 99%

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

Westerhausen

Gärtner

Fischer

et al. 2007

Chemistry A European J

Self Cite

164

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“…We have already shown that 2 shows catalytic activity in anionic ring opening polymerization of cyclic esters. [13] Another possibility to enhance the reactivity of organocalcium compounds is to embed the calcium center in an unusual coordination sphere. Vacant coordination sites at the Lewis-acid metal center lead immediately to coordination of Lewis bases such as ethers or to a dimerization of the calcium-containing compound.…”

Section: Synthesismentioning

confidence: 99%

“…The advantage of the catalytically active complexes 2 and 3 in comparison to the already investigated calcium bis[bis-(trimethylsilyl)amide] [6,29] lies in the reduced sensitivity towards air and moisture and, therefore, an easier handling outside of a glove box seems to be possible during the polymerization experiments. Preliminary experiments support the expectation that these compounds are valuable initiators for the anionic polymerization of lactones and other cyclic ester.…”

Section: Perspectivementioning

confidence: 99%

“…[5] Another important application for organocalcium compounds focuses on their use as initiators for the anionic ring-opening polymerization of cyclic esters and lactones. [6] These arbitrarily chosen examples illustrate the wide spectrum of interest in these compounds. Whereas for the MOCVD processes the main requirements of these compounds are volatility and thermal stability, the demands for ring-opening polymerization concern their reactivity towards cyclic esters and their solubility in common organic solvents such as ethers and hydrocarbons.…”

Section: Introductionmentioning

confidence: 99%

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Organocalcium Compounds with Catalytic Activity for the Ring‐Opening Polymerization of Lactones

et al. 2003

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The equimolar reaction of calcium bis[bis(trimethylsilyl)amide] with 2,2,6,6‐tetramethylheptane‐3,5‐dione (Htmhd) in THF yields liquid mononuclear [Ca(tmhd){N(SiMe3)2}(THF)3] (1). A similar reaction in toluene with a stoichiometric ratio of 2:3 gives the dinuclear complex [{(THF)Ca}2(tmhd)2(µ‐tmhd){µ‐N(SiMe3)2}] (2). The calcium atoms of these complexes are in a distorted octahedral environment. In 2 the complex consists of two octahedra connected by a common face of one nitrogen base and two oxygen atoms; the bridging Ca−N bond lengths are extremely large. The metalation of the tetradentate Jacobsen reagent with calcium bis[bis(trimethylsilyl)amide] in 1,2‐dimethoxyethane (DME) gives the corresponding calcium complex 3, nearly quantitatively, as its DME adduct. The calcium atom is in an unusual trigonal prismatic coordination sphere. The metathesis reaction of 3 with tin(II) chloride yields the corresponding yellow tin(II) complex with the metal atom in a distorted square‐pyramidal environment. Complexes 2 and 3 show catalytic reactivity in the ring‐opening polymerization of cyclic esters such as lactones and lactides. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

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“…Another field of interest is the metal organic chemical vapour deposition, in a process to obtain thin films of calcium sulfide [4] or titanates [5]. Another important application for organocalcium compounds focuses on their use as initiators for the anionic ring-opening polymerization of cyclic esters and lactones [6]. It also important for its use as in polymerization initiators and catalysts where organocalcium complexes can have vacant coordination sites, which in turn can be filled by weakly bonding ligands, or have unusual or distorted coordination spheres at the metal center.…”

Section: Introductionmentioning

confidence: 99%

Acetate Bridged Trinuclear Zn, Ca and Mg Metal Complexes with 2- and 4-Substituted Pyridines

Escobedo-Martínez

Lozada

Gnecco³

et al. 2012

J Chem Crystallogr

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The structures of the complexes [Zn 2 (C 5 H 6 N 2 ) 2 (C 2 H 3 O 2 ) 6 Ca], compound 1; [Zn(C 7 H 10 N 2 ) 2 Cl 2 ] compound 2; and [Zn 2 (C 5 H 6 N 2 ) 2 (C 2 H 3 O 2 ) 6 Mg] compound 3 were established by spectral and X-ray diffraction studies. These complexes form part of the project of design and synthesis of new alkaline-earth metal complexes with multiple applications in the fields of catalysis, material science and biochemistry. Compound 1 crystallizes in the monoclinic space group P2 1 /c with unit cell parameters a = 11.6918(11), b = 8.2850 (8), c = 15.3472(15) Å , b = 96.4140(10)°, Z = 2. Compound 2 crystallizes in the orthorhombic space group Pccn with unit cell parameters a = 13.6485(13), b = 14.2962(14), c = 18.2459(18) Å , Z = 8. Compound 3 crystallizes in the monoclinic space group P2 1 /c with unit cell parameters a = 7.5531(8), b = 22.905 (3), c = 8.7137(9) Å , Z = 2. All three structures (1-3) were solved by direct methods and refined to R = 0.0257, 0.0346 and 0.0244, respectively. For compound 1 crystallizes with the Ca 2? ion coincident with crystallographic centre of symmetry forming a dimer. The Ca 2? ion is six-fold coordinated by three acetate ligands. The Ca polyhedron may be described as a distorted tricapped trigonal prism. The Zn 2? ion is four-fold coordinated by three O atoms from three acetate groups (atoms O 2 , O 4 and O 5 ) and an N atom from the 2-aminopyridine moiety. The Zn polyhedral may be described as a distorted tetrahedral coordination. Compound 2 crystallizes as a crystallographic C 2 -symmetric complex, in which each Zn 2? ion is bound to two 4-dimethylaminopyridine units, and two Cl -1 ions. The tetracoordinated Zn atoms adopt a distorted tetrahedral geometry. Compound 3 crystallizes with the Mg 2? ion coincident with crystallographic centre of symmetry forming a dimer. The Mg 2? ion is octahedrally coordinated by six O atoms from three acetate groups. The Zn 2? ions are in a tetrahedral geometry. In the crystal structures 1 and 3, the molecules are stabilized by N-HÁÁÁÁÁÁO; C-HÁÁÁÁÁÁO interactions. However in the crystal structure 2, the molecules are stabilized by C-HÁÁÁÁÁCl interactions.

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Cited by 53 publications

References 22 publications

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

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

Organocalcium Compounds with Catalytic Activity for the Ring‐Opening Polymerization of Lactones

Acetate Bridged Trinuclear Zn, Ca and Mg Metal Complexes with 2- and 4-Substituted Pyridines

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