Encapsulated alkaline-earth metallocenes. Synthesis, solution behavior, and solid-state structures of bis(tetraisopropylcyclopentadienyl)calcium and -barium, [(C3H7)4C5H]2Ca and [(C3H7)4C5H]2Ba

Williams, Richard; Tesh, Kris F.; Hanusa, Timothy P.

doi:10.1021/ja00013a020

Cited by 112 publications

(100 citation statements)

References 5 publications

(7 reference statements)

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“…This distance is within experimental error of the average CaϪC length observed in the other structurally characterized base-free calcocenes, i.e., (Cp 4i ) 2 Ca, [18] (Cp 3i ) 2 2 , which also contains a formally sixcoordinate calcium center. [15] The ring centroidϪCaϪring centroid angle of 166.7°is more linear than the analogous angles found in (Cp 4i ) 2 Ca [18] and Cp* 2 Ca [2] (162.3°and 147.0°, respectively). There is no evidence for excessive steric crowding in the complex, however, as the closest intramolecular methyl···methylЈ contact is at 4.0 Å ; this is equal to the sum of the van der Waals radii of two methyl groups.…”

Section: (Cp 3si ) 2 Ca (1)supporting

confidence: 73%

“…The average BaϪC(CpЈ) distance in 3 of 3.01(2) Å and the BaϪring centroid distance of 2.75 Å are longer than those observed in the formally six-coordinate (Cp 4i ) 2 Ba [2.94(2) Å and 2.68 Å , respectively]. [18] The BaϪC distance is similar to that found in the sterically crowded metallocene [(iPr) 5 (1), respectively]. [18] The ring centroidϪBaϪring centroid angle of 162.2°in 3 is considerably wider than the angle in either (Cp 4i ) 2 Ba (154.2°) [18] or Cp* 2 Ba (131.0°).…”

Section: (Cp 3si ) 2 Ba (3)mentioning

confidence: 83%

“…In contrast, enhanced air stability has been reported for both the octa-and decaisopropylated alkalineearth metallocenes. [18,19] The magnesium compound (Cp 3Si ) 2 Mg was reported some time ago by Jutzi and co-workers. [16] Of the remaining [16] [ 16] this work this work this work [a] Two independent molecules (a and b) are found in the unit cell.…”

Section: Introductionmentioning

confidence: 99%

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A Homologous Series of Base‐Free Organo(alkaline‐earth) Metallocenes: Synthesis and Molecular Structures of [1,2,4‐(SiMe₃)₃C₅H₂]₂(Ca, Sr, Ba)

et al. 2003

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Bis[1,2,4‐tris(trimethylsilyl)cyclopentadienyl] complexes [1,2,4‐(SiMe3)3C5H2]2Ae [(Cp3Si)2Ae; Ae = Ca (1), Sr (2), Ba (3)] are isolated from the 2:1 reaction of K[Cp3Si] and AeI2 in diethyl ether. Under the same reaction conditions used for the heavier metallocenes, the corresponding (Cp3Si)2Be compound was not formed, although calculations suggest that the beryllocene would be sterically feasible. Compound 1 crystallizes as a bent monomer from hexanes (ring centroid−Ca−ring centroid = 166.7°) with two η5‐Cp3Si ligands on the calcium atom [Ca−C(av) = 2.63(2) Å]. Metallocene 2, the first crystallographically characterized example of an unsolvated strontocene, is also isolated as a bent monomer (159.4°) from hexanes with two η5‐Cp3Si ligands on the strontium atom [Sr−C(av) = 2.819(2) Å]. Compound 3 crystallizes on sublimation as a coordination dimer in which each barium atom is flanked by two η5‐Cp3Si rings [Ba−C(av) = 3.01(2) Å] and one methyl group from a neighboring Cp′ ring; the intermolecular Ba···C(methyl)′ distance is 3.275(6) Å. The amount of bending observed in 1−3 and other Group‐2 metallocenes varies with the metals, the steric bulk of the cyclopentadienyl ligands, and crystal packing effects, and is not easily predictable. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

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Section: (Cp 3si ) 2 Ca (1)supporting

confidence: 73%

Section: (Cp 3si ) 2 Ba (3)mentioning

confidence: 83%

Section: Introductionmentioning

confidence: 99%

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A Homologous Series of Base‐Free Organo(alkaline‐earth) Metallocenes: Synthesis and Molecular Structures of [1,2,4‐(SiMe₃)₃C₅H₂]₂(Ca, Sr, Ba)

et al. 2003

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“…As part of our studies of organoalkaline-earth chemistry [10][11][12][13], we sought to develop a synthetic approach to metallocenes with pendant groups that could be used with all three of the heavier metals (Ca-Ba). and that would be applicable to a range of cyclopentadienyl derivatives.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and X-ray crystal structures of alkaline-earth metallocenes with pendant substituents

Hays

Hanusa

Nile

1996

Journal of Organometallic Chemistry

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“…22 The potassium salt of 1,3-di-t-butylcyclopentadiene was prepared in an exactly similar fashion. The sodium salt of the 2,2,6,6-tetramethyl-3,5-heptanedione was prepared by modification of the literature procedure for Na(hfac).…”

mentioning

confidence: 99%

Synthesis of Heteroleptic Strontium Complexes Containing Substituted Cyclopentadienyl and β-Diketonate Ligands

George¹,

Park²,

Kim³

et al. 2013

Bulletin of the Korean Chemical Society

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The interest in the chemistry and development of strontium precursors for atomic layer deposition (ALD) or chemical vapor deposition (CVD) were driven by several applications such as, SrTiO 3 for dynamic random access memories (DRAM), 1 ferroelectrics such as Ba In the synthesis and application of ALD precursor, it is important that the compound should have a good volatile character, stability, and chemical reactivity to allow formation of the target films. In common, the requirements for precursor were achieved by introducing functionalities to the ligands of the homoleptic compounds. But due to the uniformity of the ligands, it is difficult for homoleptic metal precursor to adopt a selective dissociation of one of the ligands. In heteroleptic metal precursors, the difference in reactivity of the ligands leads to a selective dissociation of one of the ligands over the other. On a substrate surface this ability of heteroleptic metal precursors may give more precise selflimiting character which results in formation of high quality films.The most common volatile precursors of strontium were synthesized using β-diketonates like 2,2,6,6-tetramethyl-3,5-heptanedione 7,8 and highly substituted cyclopentadienes. 9The studies 10 show that the significant carbon contamination exists on the films in ALD process using strontium β-diketonate complexes, due to the stronger metal-ligand bond and weaker bonds within the ligands, as a result, the ligand bonds breaks before metal-ligand bond. In substituted cyclopentadienyl strontium complexes, the metal-ligand bond dissociation occurs much easier due to the comparatively weaker nature of the bond and stronger intraligand interactions. We expect the combination of β-diketonate ligands with substituted cyclopentadienyl ligands can bring stability, and significantly lower the ligand dissociation energy and the carbon contamination. We selected the substituted cyclopentadiene and 2,2,6,6-tetramethyl-3,5-heptanedione (tmhdH) as ligands for synthesizing heteroleptic strontium precursors. Herein, we report synthesis of strontium complexes containing tri-isopropylcyclopentadienyl and 2,2,6,6-tetramethyl-3,5-heptanedionate as well as 1,3-di-t-butylcyclopentadienyl and 2,2,6,6-tetramethyl-3,5-heptanedionate.It has been well known that the stability of strontium complexes depends on the steric effects of the ligands and its ability to shield the central metal atom as well as metalligand bond strength. Among them, the ligand's steric factor is very important in precursor chemistry to prevent the complexes from forming the oligomers that ultimately lead to low volatility. So the use of substituted cyclopentadienyl ligands with sterically bulky 2,2,6,6-tetramethyl-3,5-heptanedionate (tmhd) should provide the much needed "encapsulation" to larger alkaline earth metal. To get the desired products the reactions were carried out by substitution of iodide ions from strontium iodide (SrI 2 ) one by one, first with substituted cyclopentadienyl potassium salt and then with sodium salt of 2,2,6,6-te...

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Encapsulated alkaline-earth metallocenes. Synthesis, solution behavior, and solid-state structures of bis(tetraisopropylcyclopentadienyl)calcium and -barium, [(C3H7)4C5H]2Ca and [(C3H7)4C5H]2Ba

Cited by 112 publications

References 5 publications

A Homologous Series of Base‐Free Organo(alkaline‐earth) Metallocenes: Synthesis and Molecular Structures of [1,2,4‐(SiMe₃)₃C₅H₂]₂(Ca, Sr, Ba)

A Homologous Series of Base‐Free Organo(alkaline‐earth) Metallocenes: Synthesis and Molecular Structures of [1,2,4‐(SiMe₃)₃C₅H₂]₂(Ca, Sr, Ba)

Synthesis and X-ray crystal structures of alkaline-earth metallocenes with pendant substituents

Synthesis of Heteroleptic Strontium Complexes Containing Substituted Cyclopentadienyl and β-Diketonate Ligands

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Encapsulated alkaline-earth metallocenes. Synthesis, solution behavior, and solid-state structures of bis(tetraisopropylcyclopentadienyl)calcium and -barium, [(C3H7)4C5H]2Ca and [(C3H7)4C5H]2Ba

Cited by 112 publications

References 5 publications

A Homologous Series of Base‐Free Organo(alkaline‐earth) Metallocenes: Synthesis and Molecular Structures of [1,2,4‐(SiMe3)3C5H2]2(Ca, Sr, Ba)

A Homologous Series of Base‐Free Organo(alkaline‐earth) Metallocenes: Synthesis and Molecular Structures of [1,2,4‐(SiMe3)3C5H2]2(Ca, Sr, Ba)

Synthesis and X-ray crystal structures of alkaline-earth metallocenes with pendant substituents

Synthesis of Heteroleptic Strontium Complexes Containing Substituted Cyclopentadienyl and β-Diketonate Ligands

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A Homologous Series of Base‐Free Organo(alkaline‐earth) Metallocenes: Synthesis and Molecular Structures of [1,2,4‐(SiMe₃)₃C₅H₂]₂(Ca, Sr, Ba)

A Homologous Series of Base‐Free Organo(alkaline‐earth) Metallocenes: Synthesis and Molecular Structures of [1,2,4‐(SiMe₃)₃C₅H₂]₂(Ca, Sr, Ba)