Intramolecular C–O Insertion of a Germanium(II) Salicyl Alcoholate: A Combined Experimental and Theoretical Study

The synthesis of germanium(II) 2-tert-butyl-4-methyl-6-(oxidomethyl)phenolate (1) starting from Ge[N(SiMe3)2]2 and the corresponding salicyl alcohol is reported. Compound 1 undergoes an intramolecular oxidative insertion reaction of germanium into a C–O bond to result in a cyclic germanium(IV) tetraoxidogermocane (2). Addition of 3-tert-butyl-2-hydroxy-5-methylbenzyl alcohol to either compound 1 or 2 gave a spirocyclic monoorgano dioxagermine (3). The results of 1H NMR spectroscopic studies and DFT-D calculations are in agreement with the proposed reaction cascade in which the novel germylene 1 is first converted into the germocane 2 followed by reaction with 3-tert-butyl-2-hydroxy-5-methylbenzyl alcohol to finally provide compound 3. Addition of 4-(dimethylamino)pyridine to a solution of germylene 1 resulted in the formation of an air-stable monomeric 1:1 complex (4). The characterization of compounds 1–4 by single-crystal X-ray diffraction analysis, thermal analysis, and 1H NMR, 13C{1H} NMR, and ATR-FTIR spectroscopy is presented.