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.