Disilicon tetroxide (Si2O4) is not supposed to exist just like the carbon analogue 1,3-dioxetanedione. But why not give it a try. The research group of Gregory Robinson reporting the synthesis of a stabilised silicon oxide (DOI) has had already discovered carbene-stabilized disilicon L:Si=Si:L with L = :CN(2,6-Pri2C6H3)CH2 back in 2007 (DOI). In 2013 they were able to remove carbene-stabilised diphosphorous tetroxide (from the diphosphorous precursor) from their bucket list as well (DOI).
In the new work, carefully adding oxygen to L:Si=Si:L in toluene at room temperature was sufficient for the silicon tetroxide compound to materialise in a 38% yield. Synthetic details: volatiles were removed immediately in order to avoid excess oxygen. Color changes from dark red to pale yellow. Curiously, according to suppl info the compound was isolated by extraction with THF after adding hexane when THF, hexane and toluene are all supposed to mix.
The stability of the new compound is derived from steric shielding of the bulky ligands preventing the reactive Si=O groups from polymerising.
24 April: Note added on isolation of the compound.