Digermylene Oxide Complexes: Facile Synthesis and Reactivity

A simple heating of aminotroponiminate (ATI) ligand stabilized germylene monochlorides [(R)2­ATIGe­Cl] (R = t-Bu 1, i-Bu 2) with an excess of potassium hydroxide in toluene resulted in the first ATI ligand stabilized digermylene oxides [{(R)2­ATIGe}2­O] (R = t-Bu 3, i-Bu 4), respectively. Reaction of compound 3 with elemental sulfur and selenium gave the first germaacid anhydride complexes [{(t-Bu)2­ATIGe­(E)}2­O] (E = S 5, Se 6) with (S)­Ge–O–Ge­(S) and (Se)­Ge–O–Ge­(Se) moieties, respectively. The digermylene oxide complexes 3 and 4 and germaacid anhydride complexes 5 and 6 were characterized by multinuclear NMR spectroscopy and single-crystal X-ray diffraction analysis. In its 77Se NMR spectrum, compound 6 showed a resonance at −78.9 ppm. The Ge–O–Ge bond angles in compounds 5 and 6 are 178.66(2)° and 179.81(2)°, respectively. To understand further the bonding features, DFT calculations followed by MO, AIM, and NBO analysis were carried out on compounds 3, 5, and 6. The computed Wiberg bond indices of Ge–O bonds are slightly less than 0.5 in all the aforementioned compounds, and the same for the GeE bonds in compounds 5 and 6 are close to 1.4.