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The determination of the crystal structure of acetyltriphenylgermane by x-ray diffraction Harrison, Roy William

Abstract

Acetyltriphenylgermane, (C₆H₅)₃GeCOCH₃, crystallizes in the monoclinic system with a = 15.30, b = 14.53, c = 7.68Å, and β = 94.8°. The space group is P2₁/c and there are four molecules per unit cell, thus each molecule forms an asymmetric unit in the cell. The intensities of 2537 reflections were measured by means of a scintillation counter using CuKα radiation. The structure was determined by heavy atom Patterson and Fourier synthesis and refinement was by least-squares methods. The final discrepancy, R, for 1834 observed reflections is 0.075. The compound was found to be tetrahedral about the germanium atom, with only small deviations caused by the spreading of the phenyl rings. The phenyl rings are planar with a mean C-C bond distance of 1.383 Å, mean C-C-C bond angle of 120.0°, and a mean C-H bond distance of 1.09 Å. Intermolecular interaction causes one ring to deviate from a symmetric propeller orientation. Two Ge-C bond distances were found: Ge-Cphenyl distance of 1.945 Å and Ge-Cacetyl distance of 2.011 Å. The longer Ge-C bond is attributed to contribution from a resonance structure in which there is no formal bond between germanium and the carbonyl carbon, resulting in a partial negative charge on the oxygen and a partial positive charge on the germanium. This is supported by the electronegativity difference between carbon and germanium. The C=O bond distance is 1.20 Å.

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