Chemistry of recoiling silicon atoms. V. Product-forming reactions in phosphine-silane mixtures

Abstract

Product studies on reactions of recoiling silicon atoms in binary mixtures of phosphine, the silicon precursor, and silane, disilane, and trisilane, respectively, support a mechanism for the product-forming steps involving silylene 81SiH2 as the principal reactive intermediate which gives rise to the observed products. In each case the major product is a next-higher homolog of the starting silane, the expected product of Si-H insertion by 31SiH2. Four other mechanisms are discussed and rejected on the basis of product studies and scavenger experiments. Competition experiments in ternary phosphine-silane-disilane and quaternary phosphinesilane-disilane-nitric oxide mixtures are correlated by a kinetic scheme for the product-determining steps involving a single intermediate. It is suggested that the product-determining steps are the product-forming steps and that the single kinetically important intermediate is 81SiH2. Formation of lower homologs of the major products is explained by the unimolecular dissociation of vibrationally excited silylene insertion products.(1) AEG Technical Report No. COO-1713-24, This work has been carried out with financial support under contract from the U. S. Atomic Energy Commission.

An evaluation of the kinetic data for hydrogen abstraction from silanes in the gas phase

“…42 Zeck et aL 'a have measured the relative efficiencies of H-abstraction from eight hydrides. They found that there was a correlation between the efficiency of the reaction and the bond dissociation energy of the substrate molecule: Sill, was much more reactive than, for example, CH4, as might be expected from the difference of about 8 kcal tool -t in their bond dissociation energies.…”

Reactions of recoiling silicon atoms with phosphine-diene mixtures and the question of silylene intermediates

“…Recoil losses from 1:1 PH3-SiH4 mixtures in the 6-mm ampules have previously been determined to be negligible at 1000 Torr total pressure, 9 ± 1% at 500 Torr, and 41 ± 4% at 200 Torr. 6 Fast Neutron Irradiations. Sets of ampules were rotated to equalize neutron flux during the ca.…”

Ground electronic state of silylene

“…was developed by Gaspar and coworkers,[8][9][10][11][12] (ii) the decomposition studies stemming from the pyrolysis and photolysis of compounds such as SiH 4 and Si2H6. [13][14][15][16][17] Si2H6 -^> SiH-+ SiH4…”