Utility of trichloroisocyanuric acid in the efficient chlorination of silicon hydrides

Abstract

The potential of trichloroisocyanuric acid (TCCA) as a chlorination agent for efficient conversion of Si–H functional silanes and siloxanes to the corresponding Si–Cl functional moieties was explored. In comparison to methods using other chlorinating agents, TCCA is inexpensive, results in a much faster reaction and produces a high purity product with a conversion that is essentially quantitative. A variety of chloro derivatives of linear and cyclic structures have been synthesized from silicon hydrides using this reagent with impressive yields that typically exceed 90%: PhSiCl 3 (97.5%); PhMeSiCl 2 (95.5%); Ph 3SiCl (97.5%); Vi 3SiCl (98.7%); (EtO) 3SiCl (99.7%); t-Bu 3SiCl (∼100%); (MeClSiO) 4 (86.5%); (MeClSiO) 5 (95%); (MeClSiO) 7 (96.5%); Ph(OEt) 2SiCl (98%); ClMe 2SiOSiMe 2Cl (98.6%); ClMe 2SiOSiMeClOSiMe 2Cl (94.6%); ClMe 2Si(OSiMeCl) 2OSiMe 2C l (92.3%); (Me 3SiO) 3SiCl (97%); Me 3SiOSiClPhOSiMe 3 (99%); Me 3SiO(SiMeClO) 3SiMe 3 (95.7%); ClSi(OSiMe 3) 2OSi(OSiMe 3) 2Cl (93.6%). For monohydridosilanes, dichloromethane (CH 2Cl 2) was a suitable solvent in which nearly quantitative conversion was observed within several minutes following the addition of the silanes to TCCA. For certain cyclic and linear siloxanes, and especially silanes containing multiple hydrogen atoms on the same silicon for which the reaction is sluggish in CH 2Cl 2, tetrahydrofuran (THF) was the preferred solvent. For a sterically demanding silane that did not undergo chlorination even in THF viz., HSi(OSiMe 3) 2O–Si(OSiMe 3) 2H, 1,2-dichloroethane was the best solvent.