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Disilicon tetroxide

23 April 2015 - Chemical Zoo

disilicon tetroxide.PNGDisilicon 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.


04 April 2015 - Chemical Zoo

You would expect that by now chemists haver tackled all small molecules and have ventured on with the larger ones. This is far from the truth. Simple binary compounds continue to pose problems and large tracts of the small ternary compound landscape are still unknown to science. It is therefore a happy occasion to welcome into the expanding family of chemical compounds: ZrIrSb as reported by Gautier et al. (doi) They have been intelligently exploring a chemical space defined by a known series of binary AX compounds relevant as semiconductors such as ZnO expanded by cobalt, rhodium or iridium. Of the initial set of 483 potential compounds only 83 have ever been synthesised, for example LaNiSb or ZrPtSi so it was clear work was needed to be done.

Of the possible remaining 400 compounds the thermodynamic stability was calculated by DTF, basically the energy of the most likely crystal structure (together with phonon stability) compared to that of the constituents or any other compound configuration (unary, binary) from what can be understood from the article. 54 compounds survived this screening, the others are deemed incurably unstable. For example the hypothetical CaNiO exists more happily as a mixture of CaO and elementary nickel.

In the second phase several compounds were synthesised using arc melting and quartz-tube annealing and ZrIrSb was one of the new compounds found to form a single phase. Identification was based on XRD AND SAED. The crystal types were determined by TEM. Additional bonus for ZrIrSb, it is not only a conductor , it is also a transparent conductor.