A germanium µ-oxo chloro dimer en route to a heavier phosgene analogue and 1,3-digermadioxetane dications

Heavier analogues of carbonyl compounds are challenging to isolate due to the intrinsic instability of E[double bond, length as m-dash]O double bonds (E = Si-Pb). Herein, we demonstrate that a germanium(iv) µ-oxo chloro dimer, [YGe(Cl)O]₂ (2), supported by an iminophosphinoyl-tethered yldiide ligand (Y = [Ph₂P(NMes)-C-PPh₃]^-), serves as a versatile platform for the generation of unprecedented germanium oxo species. Treatment of the dimer with H₂O·B(C₆F₅)₃ enables the isolation of the first example of a Lewis acid-base stabilized germaphosgene, YH → Cl₂GeO → B(C₆F₅)₃ (3), through conversion of the yldiide into a carbodiphosphorane ligand upon protonation. Furthermore, halide abstraction from dimer [YGe(Cl)O]₂ provides access to a series of unprecedented 1,3-digermadioxetane dications (4a-e), featuring a planar, square-shaped Ge₂O₂ core. Structural and computational analyses reveal highly polarized Ge-O single bonds in both systems, with no significant π-character. The strong donor ability of the ylide ligands is key to accessing compounds 3 and 4. While the newly formed carbodiphosphorane in 3 stabilizes the germaphosgene through its strong donor ability and the resulting Ge-O bond polarization, the yldiide in dimer 2 facilitates chloride abstraction and stabilizes the cationic charge in the dioxetane dications through charge delocalization into the entire ligand backbone.