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 H-1 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 singlecrystal X-ray diffraction analysis, thermal analysis, and H-1 NMR, C-13{1H} NMR, and ATR-FTIR spectroscopy is presented.