Abstract
ansa-Metallocene derivative (η5-Gaz)2Ca(THF)2 (1) (Gaz = 1,4-dimethyl-7-isopropylazulene) was synthesized by the reaction of CaI2(THF)2 with two equivalents of potassium and two equivalents of guaiazulene in THF. The ytterbium analog ansa-(η5-Gaz)2Yb(THF)2 (2a) was synthesized by the reduction of guaiazulene with ytterbium naphthalenide in THF. The recrystallization of 2a from pyridine leads to the exchange of the coordinated solvent molecules and gives ansa-(η5-Gaz)2Yb(NC5H5)2 (2b). The molecular structures of 1, 2a, and 2b were determined by X-ray diffraction analysis. The crystals of 1, 2a, and 2c consist of a racemic mixture of both R,R- and S,S-enantiomers. The calcium and ytterbium atoms η5-coordinate the five-membered rings of the guaiazulene ligands. The 1H NMR spectroscopic and X-ray diffraction data unambiguously confirm the exclusive formation of N2-symmetric ansa-metallocenes in these reactions. The reaction of compound 1 with Me3SiCl in THF occurs with retention of the N—N bond between two guaiazulene moieties and affords bis(1,4-dimethyl-3-trimethylsilyl-7-isopropylazulene) (3) in high yield.
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Fedushkin, I.L., Kurskii, Y.A., Balashova, T.V. et al. Diastereoselective formation of calcium and ytterbium ansa-metallocenes via recombination of guaiazulene (Gaz) radical anions. Molecular structure of ansa-(η5-Gaz)2Ca(THF)2 and ansa-(η5-Gaz)2Yb(Py)2 (Gaz = 1,4-dimethyl-7-isopropylazulene) complexes. Russian Chemical Bulletin 52, 1363–1371 (2003). https://doi.org/10.1023/A:1024827127959
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DOI: https://doi.org/10.1023/A:1024827127959