The direct detection of germenes in solution: The photochemistry of 1,1-diphenylgermetane, arylgermasilanes, and aryldigermanes

Abstract

<p>"Silenes" and "germenes" are molecules containing Si=C and Ge=C double bonds, respectively. Some of the reactions which involve the intermediacy of these species will be reviewed, as will some of the recent efforts to characterize transient silenes and germenes and investigate the mechanisms of their more common reactions. The first part of this thesis focuses on the generation and characterization of a germanium-carbon doubly bonded species in solution. Direct irradiation of 1,1-diphenylgermetane in hexane solution in the presence or absence of aliphatic alcohols leads to products consistent with the formation of 1,1-diphenylgermene as the primary photochemical product. Nanosecond laser flash photolysis of the germetane in hexane, acetonitrile and tetrahydrofuran gives rise to the formation of a transient, assignable to the germene on the basis of its second order decay kinetics, UV spectrum (λmax = 325-nm), and the fact that its lifetime is shortened by the addition of alcohols and acetic acid. The mechanism of silene and germene dimerization reactions was investigated using 1,1-diphenylsilacyclobutane and 1,1-diphenylgermetane as precursors to 1,1-diphenylsilene and 1,1-diphenylgermene respectively. 1,1,3,3-Tetraphenyl-1,3-disilacyclobutane, -1,3-digermacyclobutane, and 1,3-germasilacyclobutane have been synthesized by direct photolysis of hexane solutions of 1,1-diphenylsilacyclobutane, 1,1-diphenylgermetane, and a 1:1 mixture of the two. The photochemistry of 1,1,1-trimethyl-2,2,2-triphenylgermasilane (Ph 3 GeSiMe3 ), 2,2,2-trimethyl-1,1,1-triphenylgermasilane (Ph 3 SiGeMe3 ), and 1,1,1-trimethyl-2,2,2-triphenyldigermane (Ph 3 GeGeMe3 ) has been studied in hydrocarbon solution by steady state and laser flash photolysis methods. The results are compared to previously reported data for the homologous disilane Ph3 SiSiMe3 , whose photolysis under similar conditions results in the exclusive formation of a 1,3,5-(1-sila)hexatriene resulting from photochemical [1,3]-trialkylsilyl migration into one of the aromatic rings. (Abstract shortened by UMI.)</p>