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- Title
One‐Step Synthesis and Schlenk‐Type Equilibrium of Cyclopentadienylmagnesium Bromides.
- Authors
Schüler, Philipp; Görls, Helmar; Krieck, Sven; Westerhausen, Matthias
- Abstract
In the in situ Grignard metalation method (iGMM), the addition of bromoethane to a suspension of magnesium turnings and cyclopentadienes [C5H6 (HCp), C5H5‐Si(iPr)3 (HCpTIPS)] in diethyl ether smoothly yields heteroleptic [(Et2O)Mg(CpR)(μ‐Br)]2 (CpR=Cp (1), CpTIPS (2)). The Schlenk equilibrium of 2 in toluene leads to ligand exchange and formation of homoleptic [Mg(CpR)2] (3) and [(Et2O)MgBr(μ‐Br)]2 (4). Interfering solvation and aggregation as well as ligand redistribution equilibria hamper a quantitative elucidation of thermodynamic data for the Schlenk equilibrium of 2 in toluene. In ethereal solvents, mononuclear species [(Et2O)2Mg(CpTIPS)Br] (2'), [(Et2O)nMg(CpTIPS)2] (3'), and [(Et2O)2MgBr2] (4') coexist. Larger coordination numbers can be realized with cyclic ethers like tetrahydropyran allowing crystallization of [(thp)4MgBr2] (5). The interpretation of the temperature‐dependency of the Schlenk equilibrium constant in diethyl ether gives a reaction enthalpy ΔH and reaction entropy ΔS of −11.5 kJ mol−1 and 60 J mol−1, respectively.
- Subjects
HEAT of reaction; EQUILIBRIUM; ETHER (Anesthetic); CYCLIC ethers; BROMIDES
- Publication
Chemistry - A European Journal, 2021, Vol 27, Issue 62, p15508
- ISSN
0947-6539
- Publication type
Academic Journal
- DOI
10.1002/chem.202102636