Disilane Cleavage with Selected Alkali and Alkaline Earth Metal Salts

• Published in: Chemistry : a European journal Vol. 25; no. 57; pp. 13202 - 13207
• Main Authors: Santowski, Tobias, Sturm, Alexander G., Lewis, Kenrick M., Felder, Thorsten, Holthausen, Max C., Auner, Norbert
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 11.10.2019; John Wiley and Sons Inc
• Subjects: alkali and alkaline earth metal salts; Alkali metals; Alkaline earth metals; Chemistry; Chlorine; Cleavage; disilane cleavage; Disproportionation; Earth; Lithium; Lithium chloride; lithium hydride; Lithium hydrides; Metal hydrides; Metals; monosilanes; Reduction; Reintroduction; Salts; Siloxanes; disilane cleavage; lithium chloride; lithium hydride; monosilanes; alkali and alkaline earth metal salts
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201902722

The industry‐scale production of methylchloromonosilanes in the Müller–Rochow Direct Process is accompanied by the formation of a residue, the direct process residue (DPR), comprised of disilanes MenSi2Cl6‐n (n=1–6). Great research efforts have been devoted to the recycling of these disilanes into monosilanes to allow reintroduction into the siloxane production chain. In this work, disilane cleavage by using alkali and alkaline earth metal salts is reported. The reaction with metal hydrides, in particular lithium hydride (LiH), leads to efficient reduction of chlorine containing disilanes but also induces disproportionation into mono‐ and oligosilanes. Alkali and alkaline earth chlorides, formed in the course of the reduction, specifically induce disproportionation of highly chlorinated disilanes, whereas highly methylated disilanes (n>3) remain unreacted. Nearly quantitative DPR conversion into monosilanes was achieved by using concentrated HCl/ether solutions in the presence of lithium chloride. Too valuable for disposal or incineration: Simple recycling of the Müller–Rochow Direct Process residue with LiH yields monosilanes suitable for the reintroduction into the silicone production chain.