Organometallics, 19, 3232-3241 (2000).
© American Chemical Society, 2000
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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