Solution synthesis of calcium, strontium and barium metallocenes

doi:10.1016/S0277-5387(88)80045-7

Polyhedron

Volume 7, Issue 9, 1988, Pages 725-730

https://doi.org/10.1016/S0277-5387(88)80045-7 Get rights and content

Abstract

Bis(cyclopentadienyl)metal complexes of calcium, strontium and barium can be prepared in synthetically useful yields (> 65%) from the reaction of lithium or potassium cyclopentadienides and the appropriate metal dihalides in THF. The THF-soluble complexes (C₅H₅)₂Ca(THF)₂ and (Me₅C₅)₂M(THF)₂ (M = Ca, Sr, Ba) are extracted from the reaction of the appropriate potassium cyclopentadienide with a metal halide; the THFinsoluble (C₅H₅)₂M(THF)_x(x ≈ 1 for Sr; x ≈ 0.25 for Ba) remain after the reaction of a lithium cyclopentadienide and the metal iodide.

References (16)

R. Zerger et al.
J. Organomet. Chem.
(1974)
C.J. Burns et al.
J. Organomet. Chem.
(1987)
R.A. Andersen et al.
Acta Chem. Scand.
(1987)
W.J. Evans et al.
Organometallics
(1986)
H. Schumann et al.
Angew. Chem.
(1986)
T.J. Kealy et al.
Nature
(1951)
C.M. Lukehart
Fundamental Transition Metal Organometallic Chemistry
(1985)
W.E. Lindsell
K. Ziegler et al.
Chem. Ber.
(1956)
E.O. Fischer et al.
Chem. Ber.
(1961)

There are more references available in the full text version of this article.

Cited by (51)

Calcium, strontium, and barium
2021, Comprehensive Coordination Chemistry III
Once sidelined for their salt-like behavior, the coordination chemistry of the heavier alkaline earth metals (Ca, Sr, Ba) have come a long way with the knowledge of hundreds of well-defined molecular complexes existing at the moment. The key has been the consideration of sterically bulky and chelating ligands and coligands to address the kinetic instability which allows the isolation of such stable yet highly reactive compounds. Their significance is further enhanced by their potential applications in homogeneous catalysis. This article communicates a concise summary of those complexes involved in shaping up the modern main group chemistry.
Stability of cyclopentadienyl aryloxide complexes of calcium and barium
2009, Journal of Alloys and Compounds
The synthesis of mono(cyclopentadienyl)aryloxide complexes of calcium and barium has been investigated. The reaction of ICa(ODipp)(thf)₄ (Odipp = [2,6-iPr-OC₆H₃O]⁻) with K[C₅Me₅], (Cp^3Si)₂Ca (Cp^3Si = C₅(SiMe₃)₃H₂) with K[ODipp], and IBa(BHT)(thf)₃ (BHT = [2,6-tBu-4-Me-C₆H₂O]⁻) with K[C₅Me₅] in THF produces Cp*Ca(Odipp)(thf)₃, (Cp^3Si)Ca(Odipp)(thf)₂, and Cp*Ba(BHT)(thf), respectively. The crystal structures of the two monomeric calcium complexes are reported. All three compounds are stable against Schlenk rearrangement in THF and aromatic solvents. DFT calculations suggest that the presence of THF has less of an effect on the thermodynamics of Schlenk rearrangements of the aryloxide systems than it does on comparable Cp′CaI compounds.
Metallocenes of the alkaline earth metals and their carbene complexes
2001, Journal of Organometallic Chemistry
Novel alkaline earth metallocenes with various cyclopentadienyl ligands and their carbene adducts with 1,3-di-iso-propyl-4,5-dimethylimidazol-2-ylidene (iPr-carbene) are described. The syntheses of the magnesocenes (C₅Me₄H)₂Mg (1), (C₅Me₄tBu)₂Mg (2), and (C₅H₃-1-(SiMe₃)-3-tBu)₂Mg (3) were carried out by reaction of the corresponding cyclopentadiene with dibutylmagnesium. The calcocenes (C₅Me₄H)₂(NH₃)₂Ca (6), (C₅Me₄H)₂(NH₃)(THF)Ca (7) and the barocene (C₅Me₄tBu)₂(THF)₂Ba (13) were prepaired by reaction of calcium and barium, respectively, with the corresponding cyclopentadienes. Refluxing 7 in THF–toluene yielded the ammonia-free complex (C₅Me₄H)₂(THF)Ca (8). Metathesis reaction of (C₅Me₄iPr)Na with CaI₂ gave the calcocene (C₅Me₄iPr)₂(THF)Ca (9). (C₅Me₄tBu)₂(py)₂Ba (14) results from dissolving 13 in pyridine. 1,3-Di-iso-propyl-4,5-dimethylimidazol-2-ylidene reacted with 1, 3, 7, 8, 13, and (C₅Me₅)₂(THF)₂Sr in toluene or THF to give the air- and moisture-sensitive adducts (C₅Me₄H)₂(iPr-carbene)Mg (4), (C₅H₃-1-(SiMe₃)-3-tBu)₂(iPr-carbene)Mg (5), (C₅Me₄H)₂(iPr-carbene)Ca (10), (C₅Me₄iPr)₂(iPr-carbene)Ca (11), (C₅Me₅)₂(iPr-carbene)Sr (12), and (C₅Me₄tBu)₂(iPr-carbene)Ba (15). The novel compounds have been characterized by elemental analysis, mass spectrometry and NMR spectroscopy as well as the X-ray structures of the metallocenes (1, 2, 6, 9, 13) and the carbene adducts (4, 10, 11, 12, 15).
Synthesis and X-ray crystal structures of alkaline-earth metallocenes with pendant substituents
1996, Journal of Organometallic Chemistry
Deprotonation of [(2-C₅H₄N)CH₂CMe₂]C₅H₅ (=HCp^py) and CH₃OCH₂CH₂C₅H₅ (=HCp^§) with Ae[N(SiMe₃)₂]₂ (Ae  Ca,Sr, Ba) in toluene produces the corresponding metallocenes, Cp₂′Ae, in high yield. ¹H NMR data reveal that the calcium complex (Cp^py)₂Ca does not bind tetrahydrofuran. The solid state structures of (Cp^py)₂Sr and (Cp^§)₂Ca were obtained by single crystal X-ray analysis, and found to be monomeric, with the Lewis base substituents on the cyclopentadienyl rings coordinated to the metal centers. Crystals of (Cp^py)₂Sr grown from toluene are orthorhombic, space group Pbcn, with $a = 11.988(4) A ̊, b = 16.141(4) A ̊, c = 12.572(4) A ̊$ , $V = 2433(1) A ̊^{3}, Z = 4, R = 0.038, R_{w} = 0.043$ based on 635 observed reflections. The complex possesses a bent metallocene geometry and contains a crystallographically imposed two-fold rotation axis passing through the strontium. The average SrC and SrN distances are 2.85(1) and 2.660(7) Å respectively, and the ring centroid-Sr-ring centroid angle is 141.1°. Crystals of (Cp^§)₂Ca grown from toluene are monoclinic, space group $P2_{1} n$ , with $a = 6.912(4) A ̊, b = 15.114(2) A ̊, c = 15.435(3), β = 100.34(2)°, V = 1586.3(9) A ̊^{3}, Z = 4, R = 0.041, R_{w} = 0.048$ based on 1318 observed reflections. The complex also has a bent metallocene geometry, with average CaC and CaO distance are 2.670(6) and 2.407(3) Å respectively; the ring centroid-Ca-ring centroid angle is 136.6°.
Bis- and tris(pyrazolyl)borate complexes of the heavier alkaline-earth elements Ca, Sr and Ba
1996, Polyhedron
Sandwich complexes of the composition MTp₂* [Tp*hydrotris(3,5-dimethylpyrazolylborate ; MCa, 1 ; Sr, 2 ; Ba, 3] have been generated by the direct reaction of the iodides MI₂ with KTp*. Attempts to prepare the half-sandwich compounds MTp*(I) have met with no success when MCa, Sr, but the reaction of BaI₂ with 1 equiv. of KTp* in THF produced BaTp*(I)(THF)_n (4a), which can be readily converted into the related adduct BaTp*(I)(HMPA)₂ [4b, HMPAOP(NMe₂)₃]. The above compounds have been characterized by analytical and spectroscopic methods, and the structures proposed have been confirmed by X-ray studies carried out with the Ba derivatives 3 and 4b. Attempts to derivatize compounds 4 led mostly to undesired products, but treatment with KTp* and KBp* [Bp*dihydrobis(3,5-dimethylpyrazolyl)borate] resulted in the formation of 3 and BaTp*Bp*(THF), 6, respectively. Bis(pyrazolyl)borate derivatives of the composition M(Bp′)₂(THF)_n have also been obtained by the direct reaction of MI₂ (MCa, Sr, Ba) with KBp* or TlBp† [Bp†dihydrobis(3-t-butyl-pyrazolyl)borate].
In situ Grignard Metalation Method, Part II: Scope of the One-Pot Synthesis of Organocalcium Compounds
2022, Chemistry - A European Journal

View all citing articles on Scopus

View full text

Solution synthesis of calcium, strontium and barium metallocenes

Abstract

J. Organomet. Chem.

J. Organomet. Chem.

Acta Chem. Scand.

Organometallics

Angew. Chem.

Nature

Fundamental Transition Metal Organometallic Chemistry

Chem. Ber.

Chem. Ber.