The decomposition kinetics of disilane and the heat of formation of silylene

✍ Scribed by J. G. Martin; M. A. Ring; H. E. O'Neal

• Publisher: John Wiley and Sons
• Year: 1987
• Tongue: English
• Weight: 517 KB
• Volume: 19
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550190805

✦ Synopsis

The static system decomposition kinetics of disilane (Si,H, A SiH, + SiH,, 538-587 K and 10-500 Torr), are reported. Reaction rate constants are weakly pressure dependent. and best fits of the data are realized with RHKM fall-off calculations using IogA,,. = 15.75 and E l , , = 52,200 cal. These parameters yield AH$3iH2),,, = (63.5 -Eh c ) kcal mol;' where Eb,< is the activation energy for the back reaction at 550 K, M = 1 std state. Five other silylene heat-of-formation values (ranging from 63.9 -E , (.

to 66.0 -E,, kcal mol-') are deduced from the reported decomposition kinetics of trisilane and methyldisilane, and from the reported absolute and relative rate constants for silylene insertions into H, and SiH,. Assuming Eb.c = 0, an average value of AH;(SiH,) = 64.3 2 0.3 kcal mo1-l is obtained. Also, a recalculation of the activation energy for silylene insertion into H,, based in part on the new disilane decomposition Arrhenius parameters, gives (0.6 + Eb kcal m o l ~ ', in good agreement with theoretical calculations.