Molecular Structures of the Digermanes Me2XGeGeXMe2 (X = Me, Cl, and H): An Ab Initio Study Combined with Experimental Investigation by Raman Spectroscopy and Gas Electron Diffra

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• 作者：Margit H&#xf6 ; lbling ; Sarah L. Masters (né ; e Hinchley) ; Michaela Flock ; Judith Baumgartner ; Karl Hassler ; Heather E. Robertson ; Derek A. Wann
• 刊名：Inorganic Chemistry
• 出版年：2008
• 出版时间：April 21, 2008
• 年：2008
• 卷：47
• 期：8
• 页码：3023 - 3033
• 全文大小：1783K
• 年卷期：v.47,no.8(April 21, 2008)
• ISSN：1520-510X

文摘

Ab initio calculations were carried out to investigate the potential-energy surface for internal rotation of the methylated digermanes hexamethyldigermane Me₃GeGeMe₃ (1), dichlorotetramethyldigermane Me₂ClGeGeClMe₂ (2), and tetramethyldigermane Me₂HGeGeHMe₂ (3). Different basis sets [6–31+G(d), SDD, aug-cc-pVTZ] were employed at the DFT and MP2 levels of theory to optimize structures and to calculate energies and vibrational frequencies. For 1, one minimum representing a staggered structure was located on the potential-energy surface. For 2 and 3, antiperiplanar conformations with C₂ symmetry were found to be the global minima. Additionally, synclinal minima were located for 2 and 3 when certain basis sets were employed. Determination of structural parameters in the gas phase by gas electron diffraction confirmed the computed predictions for all three compounds. For 2 and 3, the ratios of antiperiplanar to synclinal conformer were detected to be 90:10 (328 K) and 72:28 (293 K), respectively, by gas electron diffraction. The experimentally determined GeGe bond lengths in 1, 2, and 3 in the gas phase are 241.4(1), 242.7(2) (averaged for antiperiplanar and synclinal), and 241.7(1) pm (equal for antiperiplanar and synclinal). Only averaged structures were observed, using Raman spectroscopy, for 2 and 3 because the wavenumber differences are small between conformers and there is only a small contribution from the second conformer in each case. For 2, the crystal structure was also determined by X-ray diffraction. An anticlinal structure (with Cl atoms eclipsing the C atoms) was found with a GeGe bond length of 242.1 pm.