Kinetics and mechanism of the gas phase thermal decomposition of hexachlorodisilane in the presence of iodine

Abstract

The gas phase thermal reaction of Si₂Cl₆ with I₂ has been investigated. Product analysisreveals the formation of SiCl₄ and SiCl₂I₂. The reaction rate was found to obey the rate equation –d[I₂]//_dt=_k[Si₂Cl₆] and values of k were insensitive to changes in surface-to-volume ratio. This evidence suggests the following two step mechanism Si₂Cl₆→ SiCl₂+ SiCl₄ slow (1), SiCl₂+ I₂→ SiCl₂I₂ fast. (2) From rate measurements over the temperature range 596–655 K the Arrhenius equation. log(k₁/s^–1)=(13.49 ± 0.12)–(205.9 ± 1.4 kJ mol^–1)/RT ln 10 is obtained. These figures are consistent with earlier flow studies of this reaction in the absence of scavengers. The effects of other scavengers have been briefly investigated.

The absence of an I atom displacement process suggests that the Si—Si bond in Si₂Cl₆ is much stronger than that in Si₂Me₆.