Si–C coupling reaction of polychloromethanes with HSiCl3 in the presence of Bu4PCl: Convenient synthetic method for bis(chlorosilyl)methanes

Coupling reaction of polychloromethanes CH4−nCln (n = 2–4) with HSiCl3 in the presence of tetrabutylphosphonium chloride (Bu4PCl) as a catalyst occurred at temperatures ranging from 30 °C to 150 °C. The reactivity of polychloromethanes increases as the number of chlorine-substituents on the carbon increases. In the reactions of CCl4 with HSiCl3, a variety of coupling products such as bis(chlorosilyl)methanes CH2(SiCl3)(SiXCl2) [X = Cl (1a), H (1b)], (chlorosilyl)trichloromthanes Cl3CSiXCl2 [X = Cl (2a), H (2b)], and (chlorosilyl)dichloromthanes Cl2HCSiXCl2 [X = Cl (3a), H (3b)] were obtained along with reductive dechlorination products such as CHCl3 and CH2Cl2 depending on the reaction temperature. In the reaction of CCl4, 2a is formed at the initial stage of the coupling reaction and converted to give CHCl3 at low temperature of 30 °C, to give 1a, 3a, and CHCl3 at 60 °C, and to afford 1a as major product and CH2Cl2 in competition above 100 °C. Si–H bond containing silylmethanes can be formed by the H–Cl exchange reaction with HSiCl3. Reaction of CHCl3 with HSiCl3 took placed at 80 °C to give three compounds 1a, 3a, and CH2Cl2, and finally 3a was converted to give 1a and CH2Cl2 at longer reaction time. While the condition for the reaction of CH2Cl2 with HSiCl3 required a much higher temperature of 150 °C. Under the optimized conditions for synthesizing bis(chlorosilyl)methanes 1a,b, a mixture of 1a and 1b were obtained as major products in 65% (1a:1b = 64:1) and 47% (42:5) yields from the reaction of CCl4 and CHCl3 at 100 °C for 8 h, respectively, and in 41% (34:7) yield from that of CH2Cl2 at 170 °C for 12 h. In the Si–C coupling reaction of polychloromethanes with HSiCl3, it seems likely that a trichlorosilyl anion generated from the reaction of HSiCl3 with Bu4PCl is an important key intermediate.