Electronic interactions in 1-ethynyl-2-phenyltetramethyldisilanes HCCSiMe2SiMe2C6H4X |
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Authors: | Jennifer A Shaw-Taberlet Thiery Roisnel Michaela Flock Harald Stueger |
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Institution: | a UMR 6226 Sciences Chimiques de Rennes, CNRS-Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France b Institut für Anorganische Chemie, Technische Universität Graz, Stremayrgasse 16, A-8010 Graz, Austria |
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Abstract: | 1-Ethynyl-2-phenyltetramethyldisilanes HCCSiMe2SiMe2C6H4X X = NMe2 (1), H (2), CH3 (3), Br (4), CF3 (5)] are accessible from ClSiMe2SiMe2Cl, BrMgC6H4X and HCCMgBr in a two step Grignard reaction. The crystal structure of 1 as determined by single crystal X-ray crystallography exhibits a nearly planar PhNMe2 moiety and an unusual gauche array of the phenyl and the acetylene group with respect to rotation around the Si-Si bond. Full geometry optimization (B3LYP/6-31+G∗∗) of the gas phase structures of 1-5 affords minima for the gauche and the anti rotational isomers, both being very close in energy with a rotational barrier of only 3-5 kJ/mol. Experimental and calculated (time-dependent DFT B3LYP/TZVP) UV absorption data of 1-5 show pronounced electronic interactions of the HCC- and the C6H4X π-systems with the central Si-Si bond. |
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Keywords: | UV absorption spectra Disilanes Hyperconjugation DFT calculations |
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