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Alkylaluminum, -gallium, -magnesium, and -zinc monophenolates with bulky substituents

Price, Clint E., Dantas, Ana B., Powell, Douglas R., Wehmschulte, Rudolf J.
Zeitschrift für Naturforschung 2018 v.73 no.11 pp. 943-951
aluminum, aromatic hydrocarbons, crystal structure, gallium, magnesium, nuclear magnetic resonance spectroscopy, phenol, zinc
The bulky phenols 2,6-Ad₂C₆H₃OH (Ad=adamantyl), A, (2,6-Ph₂CH)₂-4-Me-C₆H₂OH, B, and (2,6-Tol₂CH)₂-4-iPr-C₆H₂OH, C, react with one equivalent of Et₃M (M=Al, Ga), Bu₂Mg and Et₂Zn to afford well-defined mono-phenolate complexes (ArOMRₙ)ₘ. The aluminum and gallium phenolates derived from the very bulky phenol A are likely monomeric in the solid state. The other compounds are dimeric with bridging phenolates. Crystal structures of compounds with phenols B and C display the dimeric M₂O₂ cores of the phenolates and illustrate some deviations for the magnesium and zinc compounds. The former possesses stabilizing Mg···C contacts with one of the flanking arene groups of the phenolate substituent, and the latter may be viewed as an intermediate between a symmetric dimer and two monomers. All compounds were characterized by ¹H and ¹³C NMR spectroscopy, and their solution spectra are in agreement with the crystal structure data.