Organometallics, 19, 3232-3241 (2000).

American Chemical Society, 2000

The Photochemistry of Group 14 1,1,1-Trimethyl-2,2,2-triphenyldimetallanes (Ph3MM'Me3; M, M' = Si, Ge). Direct Detection and Characterization of Silene and Germene Reactive Intermediates

William J. Leigh,* Nicholas P. Toltl, Paul Apodaca, Madeli Castruita and Keith H. Pannell

Contribution from the Department of Chemistry, McMaster University, Hamilton, ON  Canada L8S 4M1 and the Department of Chemistry, University of Texas at El Paso, El Paso, TX 79968-0513

Abstract: The photochemistry of trimethylsilyltriphenylgermane (Ph3GeSiMe3), triphenylsilyltrimethylgermane (Ph3SiGeMe3), and 1,1,1-trimethyl-2,2,2-triphenyldigermane (Ph3GeGeMe3) has been studied in hydrocarbon solution by steady state and laser flash photolysis methods, and is compared to previously reported data for the homologous disilane, Ph3SiSiMe3.  A variety of products are formed upon photolysis of the three compounds in the presence of 2,3-dimethyl-1,3-butadiene or chloroform, but in each case the major ones are derived from M-M’ bond homolysis and dimethyl- or diphenylgermylene extrusion.  The trapping products of the 1,3,5-(1-metalla)hexatriene derivatives formed by [1,3]-MMe3 migration into the ortho-position of one of the phenyl rings are formed as well, in yields of 9-30%.  While these experiments indicate that germylenes are formed in at least twice the yield of the 1,3,5-(1-metalla)hexatrienes, only the latter and triphenylsilyl or triphenylgermyl radicals can be detected by laser flash photolysis.  The metallaenes have been identified on the basis of their time-resolved UV absorption spectra and absolute rate constants for reaction with 2,3-dimethylbutadiene, methanol, acetone, acetic acid, oxygen, triethylsilane and carbon tetrachloride.  Radical formation is shown to result from reaction of the triplet states of these compounds, and a triplet lifetime is estimated for Ph3GeSiMe3 and compared to that of the disilane homolog.  The results of time-resolved experiments on other, related compounds are discussed in light of these results.


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