Mechanism of formation of tri- and tetrasilane in the reaction of atomic hydrogen with monosilane and the thermochemistry of the Si/sub 2/H/sub 4/ isomers

Journal Article · Thu Oct 22 04:00:00 EDT 1987 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100306a049· OSTI ID:5572076

Becerra, R; Walsh, R

Product-time evolution curves obtained in earlier studies of the Hg(/sup 3/P/sub 1/) photolysis of H/sub 2//SiH/sub 4/ mixtures have been model led with a complex mechanism in which both silylsilylene, SiH/sub 3/SiH, and disilene, H/sub 2/Si=SiH/sub 2/, play a role. Both Si/sub 2/H/sub 4/ isomers are necessary to explain the formation of primary Si/sub 3/H/sub 8/ and Si/sub 4/H/sub 10/. The source of SiH/sub 3/SiH is the decomposition of chemically activated disilane formed via silyl radical recombination. H/sub 2/Si=SiH/sub 2/ is proposed as arising via isomerization of SiH/sub 3/SiH in contrast to an earlier mechanism. Both primary and secondary product yield are fitted by the mechanism using reasonable rate constant estimates. RRKM calculations have been carried out which yield the following activation energies: Si/sub 2/H/sub 6/ ..-->.. SiH/sub 3/SiH + H/sub 2/, E/sub a/ = 56.4 +/- 2.0 kcal mol/sup -1/; SiH/sub 3/SiH ..-->.. H/sub 2/Si=SiH/sub 2/; E/sub a/ = 5.3 +/- 2.0 kcal mol/sup -1/. Together with information on reverse processes these values lead to ..delta..H/sub f//sup 0/(SiH/sub 3/SiH) = 74.6 +/- 2.0 kcal mol/sup -1/ and ..delta..H/sub f//sup 0/(H/sub 2/Si=SiH/sub 2/) less than or equal to 62.3 kcal mol/sup -1/. The mechanism and these values are in reasonable agreement with recent theoretical studies. The ..pi..-bonding energy in disilene is discussed.

• Research Organization: Univ. of Reading, England
• OSTI ID: 5572076
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 91:22; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
42 ENGINEERING
420800 -- Engineering-- Electronic Circuits & Devices-- (-1989)
ACTIVATION ENERGY
ARRHENIUS EQUATION
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DATA
ELEMENTS
ENERGY
ENTHALPY
EQUATIONS
EXPERIMENTAL DATA
FORMATION HEAT
HYDRIDES
HYDROGEN
HYDROGEN COMPOUNDS
INFORMATION
ISOMERS
KINETICS
MATHEMATICAL MODELS
NONMETALS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC SILICON COMPOUNDS
PHYSICAL PROPERTIES
REACTION HEAT
REACTION KINETICS
SILANES
SILICON COMPOUNDS
THERMODYNAMIC PROPERTIES