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Interaction of a pseudo-π C—C bond with cuprous and argentous chlorides: Cyclopropane⋯CuCl and cyclopropane⋯AgCl investigated by rotational spectroscopy and ab initio calculations

Lookup NU author(s): Dr Daniel Zaleski, John Mullaney, Dror Bittner, Dr Nick Walker, Professor Anthony Legon

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This is the final published version of an article that has been published in its final definitive form by AIP Publishing LLC, 2015.

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Abstract

Strongly bound complexes (CH2)3-MCl (M = Cu or Ag), formed by non-covalent interaction of cyclopropane and either cuprous chloride or argentous chloride, have been generated in the gas phase by means of the laser ablation of either copper or silver metal in the presence of supersonically expanded pulses of a gas mixture containing small amounts of cyclopropane and carbon tetrachloride in a large excess of argon. The rotational spectra of the complexes so formed were detected with a chirped-pulse, Fourier transform microwave spectrometer and analysed to give rotational constants and Cu and Cl nuclear quadrupole coupling constants for eight isotopologues of each of (CH2)3-CuCl and (CH2)3-AgCl. The geometry of each of these complexes was established unambiguously to have C2v symmetry, with the three C atoms coplanar, and with the MCl molecule lying along a median of the cyclopropane C3 triangle. This median coincides with the principal inertia axis a in each of the two complexes (CH2)3-MCl. The M atom interacts with the pseudo-π bond linking the pair of equivalent carbon atoms FC (F = front) nearest to it, so that M forms a non-covalent bond to one C−C edge of the cyclopropane molecule. The (CH2)3-MCl complexes have similar angular geometries to those of the hydrogen- and halogen-bonded analogues (CH2)3-HCl and (CH2)3-ClF, respectively. Quantitative details of the geometries were determined by interpretation of the observed rotational constants and gave results in good agreement with those from ab initio calculations carried out at the CCSD(T)(F12*)/aug-cc-pVTZ-F12 level of theory. Interesting geometrical features are the lengthening of the FC−FC bond and the shrinkage of the two equivalent BC−FC (B = back) bonds relative to the C−C bond in cyclopropane itself. The expansions of the FC−FC bond are 0.1024(9) Å and 0.0727(17) Å in (CH2)3-CuCl and (CH2)3-AgCl, respectively, according to the determined r0 geometries. The C‒C bond lengthening is in each case about four times that observed by similar methods in the corresponding complexes of MCl with ethyne and ethene, even though the cyclopropane complexes are more weakly bound than their ethyne and ethene analogues. Reasons for the larger increase in r(CC) in the pseudo-pi complexes are discussed.


Publication metadata

Author(s): Zaleski DP, Mullaney JC, Bittner DM, Tew DP, Walker NR, Legon AC

Publication type: Article

Publication status: Published

Journal: Journal of Chemical Physics

Year: 2015

Volume: 143

Online publication date: 30/10/2015

Acceptance date: 12/10/2015

Date deposited: 14/10/2015

ISSN (print): 0021-9606

ISSN (electronic): 1089-7690

Publisher: AIP Publishing LLC

URL: http://dx.doi.org/10.1063/1.4934539

DOI: 10.1063/1.4934539


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