Changes in the Geometries of C2H2 and C2H4 on Coordination to CuCl Revealed by Broadband Rotational Spectroscopy and ab-Initio Calculations

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• 作者：Susanna L. Stephens ; Dror M. Bittner ; Victor A. Mikhailov ; Wataru Mizukami ; David P. Tew ; Nicholas R. Walker ; Anthony C. Legon
• 刊名：Inorganic Chemistry
• 出版年：2014
• 出版时间：October 6, 2014
• 年：2014
• 卷：53
• 期：19
• 页码：10722-10730
• 全文大小：386K
• ISSN：1520-510X

文摘

The molecular geometries of isolated complexes in which a single molecule of C₂H₄ or C₂H₂ is bound to CuCl have been determined through pure rotational spectroscopy and ab-initio calculations. The C₂H₂路路路CuCl and C₂H₄路路路CuCl complexes are generated through laser vaporization of a copper rod in the presence of a gas sample undergoing supersonic expansion and containing C₂H₂ (or C₂H₄), CCl₄, and Ar. Results are presented for five isotopologues of C₂H₂路路路CuCl and six isotopologues of C₂H₄路路路CuCl. Both of these complexes adopt C_2v, T-shaped geometries in which the hydrocarbon binds to the copper atom through its 蟺 electrons such that the metal is equidistant from all H atoms. The linear and planar geometries of free C₂H₂ and C₂H₄, respectively, are observed to distort significantly on attachment to the CuCl unit, and the various changes are quantified. The 鈭?*鈭扖鈥揌) parameter in C₂H₂ (where * indicates the midpoint of the C鈮 bond) is measured to be 192.4(7)掳 in the r₀ geometry of the complex representing a significant change from the linear geometry of the free molecule. This distortion of the linear geometry of C₂H₂ involves the hydrogen atoms moving away from the copper atom within the complex. Ab-initio calculations at the CCSD(T)(F12*)/AVTZ level predict a dihedral 鈭?HCCCu) angle of 96.05掳 in C₂H₄路路路CuCl, and the experimental results are consistent with such a distortion from planarity. The bonds connecting the carbon atoms within each of C₂H₂ and C₂H₄, respectively, extend by 0.027 and 0.029 脜 relative to the bond lengths in the isolated molecules. Force constants, k_蟽, and nuclear quadrupole coupling constants, 蠂_aa(Cu), [蠂_bb(Cu) 鈥?蠂_cc(Cu)], 蠂_aa(Cl), and [蠂_bb(Cl) 鈥?蠂_cc(Cl)], are independently determined for all isotopologues of C₂H₂路路路CuCl studied and for four isotopologues of C₂H₄路路路CuCl.