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 inde pendent of total pressure (1-30 Torr) and inert buffer gas (C3H8 or SF 6). Arrhenius plots of the rate constants were slightly curved but gav e 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 associati on processes. The results are consistent with SI-H bond insertion proc esses led by the electrophilic interaction between the bonding electro n pair and the SiH2 empty p orbital.