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

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 C(2v) 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 (F)C (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 (F)C-(F)C bond and the shrinkage of the two equivalent (B)C-(F)C (B = back) bonds relative to the C-C bond in cyclopropane itself. The expansions of the (F)C-(F)C 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-π complexes are discussed.

Gas phase complexes of H3N⋯CuF and H3N⋯CuI studied by rotational spectroscopy and ab initio calculations: the effect of X (X = F, Cl, Br, I) in OC⋯CuX and H3N⋯CuX

“…The spectra of H 3 NÁ Á Á 63/65 CuF, H 3 15 NÁ Á ÁCuF and D 3 NÁ Á Á 63 CuF were averaged for 1500k, 540k and 2520k free induction decays (FIDs) respectively prior to being Fourier transformed. The spectra of H 3 NÁ Á Á 63/65 CuI, H 3 15 NÁ Á ÁCuI and D 3 NÁ Á Á 63/65 CuI were averaged for 660k, 180k and 540k FIDs respectively prior to being Fourier transformed. Structure optimizations and counter-poise corrected dissociation energies were calculated using the molpro package 27 at the CCSD(T)(F12*) level of theory, 28 a coupled-cluster method with single and double excitations, explicit correlation, 29 and a perturbative treatment of triple excitations.…”

“…An extensive and systematic study of the rotational spectra of BÁ Á ÁMX complexes, also generated by a combination of laser vaporisation and supersonic expansion, has since been performed. Complexes where the Lewis base is H 2 , 2,3 N 2 , 4 CO, 1,5,6 H 2 O, 7 H 2 S, 8 NH 3 , 9,10 C 2 H 2 , 11,12 C 2 H 4 , 13,14 or c-C 3 H 6 15 have been reported. Metal-containing (BÁ Á ÁMX) complexes have also been investigated by ab initio methods which have explored the nature of bonding interactions and the influence of the halide on the interaction between the metal and the Lewis base.…”

H3P⋯AgI: generation by laser-ablation and characterization by rotational spectroscopy and ab initio calculations

“…N 2 , OC, H 2 O, H 2 S, HCRCH, H 2 CQCH 2 , cyclopropane or NH 3 ), M = Cu, Ag or Au, and X = F, Cl or I. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] The programme has both experimental and theoretical components. The experimental approach is to produce BÁ Á ÁMX by laser ablation of the metal M in the presence of a gas pulse composed of small amounts of B and a molecular source of halogen atoms X in a large excess of argon.…”

“…There is some evidence that molecules BÁ Á ÁMX (M = Cu, Ag, or Au; X = F, Cl, or I) [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] have geometries that are isomorphic with those of their hydrogen-bonded (BÁ Á ÁHX, X is a halogen atom) 23 and halogen-bonded (BÁ Á ÁXY, XY is a dihalogen molecule) 24 counterparts, but are more strongly bound and exhibit a greater electric charge rearrangement within the diatomic subunit. Our interest here is to examine the geometry and binding strength of H 3 PÁ Á ÁAg-I and the electric charge redistribution within Ag-I that accompanies its formation.…”

A two force-constant model for complexes B⋯M–X (B is a Lewis base and MX is any diatomic molecule): Intermolecular stretching force constants from centrifugal distortion constants DJ or ΔJ

“…Recently, following the original work on complexes Rg· · ·MX and OC· · ·MX (M = Cu, Ag, or Au; X = F, Cl, Br, or I) by Gerry and co-workers, [4][5][6][7][8][9][10][11][12][13][14][15][16][17] we have been investigating systematically by rotational spectroscopy a wide range of complexes B· · ·MX involving another type of non-covalent interaction which links a coinage metal halide MX (M = Cu, Ag, or Au, X = F, Cl, or I) via the metal atom M to one of a number of small Lewis bases B (for example, B = N 2 , OC, NH 3 , HC≡ ≡CH, H 2 C= =CH 2 , (CH 2 ) 3 , H 2 O, and H 2 S). [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] In the more strongly bound of these complexes, the approximations that B is unchanged on complex formation and that the intermolecular stretching force constant k σ is very much smaller than all stretching constants of the same symmetry are not valid and in particular the order k σ ≪ k MX does not hold. In such circumstances, the Millen equations are only approximate; recent work indicates that the diatomic approximation gives better agreement with results calculated ab initio.…”