Reprinted from Organometallics, 16, 5804-5810 (1997).

American Chemical Society, 1997.

A Laser Flash Photolysis Study of the Photochemistry of Phenylethynylpentamethyldisilane. Absolute Rate Constants for Trapping of a Reactive (1-Sila)allene by Nucleophiles

Corinna Kerst, Ralph Ruffolo, and William J. Leigh*

Contribution from the Department of Chemistry, McMaster University, Hamilton, Ontario, Canada L8S 4M1

Abstract: Laser flash photolysis of nitrogen-saturated hexane solutions of pentamethyl(phenylethynyl)disilane affords a mixture of three transient species and a product which is stable on the millisecond time scale. These are assigned to the triplet state of the disilane (t ~ 5 s), 1,1-dimethyl-3-phenyl-3-(trimethylsilyl)-1-silaallene (t ~ 25 s), dimethylsilylene (t ~ 100 ns), and 1,1-dimethyl-2-phenyl-3-(trimethylsilyl)-1-silacyclopropene (t > 100 ms), respectively, on the basis of their UV spectra and reactivity toward various reagents. While previous work has shown that the 1-silaallene is formed in less than 25% yield, it can be readily observed in transient absorption experiments in spite of extensive spectral overlap with the alkynyldisilane triplet and the 1-silacyclopropene. Absolute rate constants for reaction of the silaallene with methanol, acetone, acetic acid, and oxygen in hexane solution are reported and compared to data for a related compound.