Time-resolved gas-phase kinetic studies of the reactions of silylene with disilane and trisilane

Absolute rate constants for the reactions of SiH2 with Si2H6 and Si3H8 have been determined over the temperature range 295-595 K by means of laser flash photolysis. The 193 nm UV photolyses of di- and trisilane were themselves used as the sources of SiH2. Rate constants were independent of total pressure (1-30 Torr) and inert buffer gas (C3H8 or SF6). Arrhenius plots of the rate constants were slightly curved but gave the following average parameters: Si2H6, log(A/cm(3) molecule(-1) s(-1)) = -9.51 +/- 0.04, E(a) = -1.9 +/- 0.3 kJ mol(-1); Si3H8, log(A/cm(3) molecule(-1) s(-1)) = -9.43 +/- 0.06 E(a) = -2.0 +/- 0.4 kJ mol(-1). These values show both reactions to be rapid, collisional association processes. The results are consistent with SI-H bond insertion processes led by the electrophilic interaction between the bonding electron pair and the SiH2 empty p orbital.