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.

further evidence concerning the mechanism from deuterium labeling in the products and from secondary deuterium isotope effects. We are also examining other similar systems for this effect." (10) An excited-state effect that we interpret as analogous to the interaction in intermediate IV has been reported by

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Produktanalysen bei der Reaktion von Ge‐Rückstoßatomen mit German, Digerrnan und German‐Silan‐Gemischen lassen auf einen Mechanismus mit 75GeH2 als wichtigem Zwischenprodukt schließen, das zur Bildung zum nächsthöheren Homologen des Substrats sowie zu Produkten der unimolekularen Zersetzung des höheren Homologen führt.