Polymerizations of hexamethylcyclosiloxane catalyzed by metal sulfonate/acid chloride combinations

Hexamethylcyclotrisiloxane (D3) was polymerized in bulk at 100°C, and the conversion was monitored by 1H‐NMR spectroscopy. Various metal triflates, which were inactive as neat salts, were combined with chlorosilanes, chlorostannanes, phenyl phosphonyl chloride, and carboxylic acid chlorides, which were also inactive when added alone. Most 1 : 1 combinations proved to produce active catalysts for the ring‐opening polymerization of D3. When the anions of sodium salts were varied alkylsulfonates and the sulfates were more reactive than the triflate. The samarium triflate/diphenyldichlorosilane combination was found to be the most reactive catalyst on the basis of the triflate ions. Regardless of the catalyst combination, the main reaction products in the early stages of all polymerizations were octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5). The polymerization mechanism is discussed. The reactive catalyst combinations also polymerized D4 at 100°C.