Activation of carbon-hydrogen bonds of aromatic rings using calcium atoms

Mochida, Kunio; Hiraga, Y.; Takeuchi, Hidenori; Ogawa, Hiroyuki

doi:10.1021/om00154a005

Cited by 41 publications

(23 citation statements)

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“…Also a beryllium hydride stabilized with a scorpionate ligand (Tp t Bu ) has been reported ( 2 ) 4g. Although soluble arylcalcium hydrides (prepared by activation of the CH bond with calcium vapor) have been reported,4h,i no NMR spectroscopic or structural proof was available. Herein we describe the synthesis and characterization of a well‐defined soluble calcium hydride complex.…”

Section: Methodsmentioning

confidence: 99%

Rational Design of a Well‐Defined Soluble Calcium Hydride Complex

2006

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There is a wealth of information on transition-metal hydride complexes, a field driven by numerous applications in catalytic processes.[1] Recently, significant progress has also been made in the syntheses of lanthanide hydride complexes.[2] The area of main-group metal hydride complexes is biased in the sense that p-block metal hydrides are much better documented [3] than s-block metal hydrides, for which only few examples have been reported. [4] There are two important reasons for this imbalance: 1) relatively small bond energies in these predominantly ionic complexes allow for facile ligand exchange and thus formation of ligand-free metal hydride (this holds especially for the larger metals) and 2) very high lattice energies for early-main-group metal hydrides result in immediate precipitation of [MH x ] 1 . Consequently, the few examples of early-main-group metal hydrides all show the hydride encapsulated in mixed aggregates. A well-defined Li-Al-hydride [4a] cluster, a lithium amide-hydride aggregate [4b,c] and the alkoxide-hydride cluster (tBuOLi) 16 (LiH) 17 [4d] have been described. A magnesium hydride was found in an "inverse crown ether", that is, encapsulated in a ring that also contains metal ions (1).

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Section: Methodsmentioning

confidence: 99%

Rational Design of a Well‐Defined Soluble Calcium Hydride Complex

2006

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“…With only few exceptions, this area is virtually unexplored. PhMgH and PhCaH appeared in literature already some years ago, however, no NMR spectroscopic or structural proof has been presented 5a,b. A crystalline complex of composition [CpMgH(thf)] was characterised by NMR spectroscopy and its reduction chemistry has been investigated 5c.…”

Section: Introductionmentioning

confidence: 99%

Hydrocarbon‐Soluble Calcium Hydride: A “Worker‐Bee” in Calcium Chemistry

Spielmann

Harder

2007

Chemistry A European J

137

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The reactivity of the hydrocarbon-soluble calcium hydride complex [{CaH(dipp-nacnac)(thf)}(2)] (1; dipp-nacnac=CH{(CMe)(2,6-iPr(2)C(6)H(3)N)}(2)) with a large variety of substrates has been investigated. Addition of 1 to C=O and C=N functionalities gave easy access to calcium alkoxide and amide complexes. Similarly, reduction of the C[triple chemical bond]N bond in a cyanide or an isocyanide resulted in the first calcium aldimide complexes [Ca{N=C(H)R}(dipp-nacnac)] and [Ca{C(H)=NR}(dipp-nacnac)], respectively. Complexation of 1 with borane or alane Lewis acids gave the borates and alanates as contact ion pairs. In reaction with epoxides, nucleophilic ring-opening is observed as the major reaction. The high reactivity of hydrocarbon-soluble 1 with most functional groups contrasts strongly with that of insoluble CaH(2), which is essentially inert and is used as a common drying agent. Crystal structures of the following products are presented: [{Ca{OC(H)Ph(2)}(dipp-nacnac)}(2)], [{Ca{N=C(H)Ph}(dipp-nacnac)}(2)], [{Ca{C(H)=NC(Me)(2)CH(2)C(Me)(3)}(dipp-nacnac)}(2)], [{Ca{C(H)=NCy}(dipp-nacnac)}(2)], [Ca(dipp-nacnac)(thf)](+)[H(2)BC(8)H(14)](-) and [{Ca(OCy)(dipp-nacnac)}(2)]. The generally smooth and clean conversions of 1 with a variety of substrates and the stability of most intermediates against ligand exchange make 1 a valuable key precursor in the syntheses of a wide variety of beta-diketiminate calcium complexes.

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“…Mochida originally proposed that the product from the reaction between benzene and calcium atoms was ''PhCaH'', [9] but he failed to isolate this compound. Instead, it was allowed to react with D 2 O and SiMe 3 Cl.…”

Section: Composition Of Arylcalcium Hydridesmentioning

confidence: 99%

“…This technique has received only sporadic attention to date. In the late 1980s, MVS was used to prepare [Ca(cot)(THF) n ] [6] and the bis(cyclopentadienyl)-calcium complex [Ca{η-C 5 H 3 -1,3-(SiMe 3 ) 2 } 2 (THF)], [7] and more recently [Ca{CH(SiMe 3 ) 2 } 2 (THF) 3 ], [8] while in the mid 1980s Mochida et al [9] reported the CϪH bond activation of benzene by calcium atoms to form PhCaH, which was not isolated but characterised by its organic products as outlined in Figure 2. In these systems the high reactivity of calcium atoms is stored in the products' highly reactive bonds.…”

Section: Introductionmentioning

confidence: 99%

Arylcalcium Hydrides as Precursors to Alkoxides and Aryloxides of Calcium

2003

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Calcium atoms react with +I-substituted benzene derivatives under cocondensation conditions to yield arylcalcium hydrides. With toluene, tert-butylbenzene, and trimethyl(phenyl)silane the reaction showed no selectivity for C−H activation, resulting in the formation of each of the three possible isomers, while with m-xylene the reaction resulted in selective activation of the bond meta to the CH 3 groups. Treatment of (tert-butylphenyl)calcium hydride with di-and trisubstituted phenols such as 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-4-methylphenol, and 2,4,6-tri-tert-butylphenol resulted in the formation of calcium aryloxides in yields Ͼ 95%.[Ca(2,4,6-tBu 3 C 6 H 2 O) 2 (THF) 3 ] crystallises from a THF solution as a distorted trigonal bipyramid, with two THF ligands in the trans-axial positions and the third THF ligand and both aryloxide groups in equatorial positions. The Ca−O Aryl bond

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Activation of carbon-hydrogen bonds of aromatic rings using calcium atoms

Cited by 41 publications

References 0 publications

Rational Design of a Well‐Defined Soluble Calcium Hydride Complex

Rational Design of a Well‐Defined Soluble Calcium Hydride Complex

Hydrocarbon‐Soluble Calcium Hydride: A “Worker‐Bee” in Calcium Chemistry

Arylcalcium Hydrides as Precursors to Alkoxides and Aryloxides of Calcium

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