The Study of Noble Gas – Noble Metal Halide Interactions: Fourier Transform Microwave Spectroscopy of XeCuCl Julie M. Michaud and Michael C. L. Gerry University of British Columbia, Vancouver, BC Canada June 2005 International Symposium on Molecular Spectroscopy

2 XeCuCl Anticipated properties:  Short Xe-Cu bond length;  Small centrifugal distortion constant;  Large changes in nuclear quadrupole coupling constants ( 131 Xe, Cu and Cl) on bond formation;  Significant theoretical evidence of strong interactions between the Xe and Cu atoms in XeCuCl.

3 The Experiment

4 132 Xe 63 Cu 35 Cl Spectrum Natural abundance: 14.1% I( 63 Cu) = 3/2 I( 35 Cl) = 3/2 Total of 10 transitions in this one spectrum

5 131 Xe 63 Cu 35 Cl Spectrum Natural abundance: 11.1% I( 131 Xe) = 3/2 I( 63 Cu) = 3/2 I( 35 Cl) = 3/2 Total of 15 transitions in this one spectrum

6 Representative Spectroscopic Constants Parameter 129 Xe 63 Cu 35 Cl 131 Xe 63 Cu 35 Cl 132 Xe 63 Cu 35 Cl B o /MHz (9) (2) (5) D J /kHz0.0794(7)0.104(2)0.0782(4) eQq(Cu) /MHz41.81(9)41.6(1)41.57(6) eQq(Cl) /MHz-26.10(6)-26.4(1)-26.01(4) eQq( 131 Xe) /MHz--81.4(2)- eQq( 63 Cu) /MHz = 16.17eQq( 35 Cl) /MHz = Nuclear quadrupole coupling constants of the CuCl monomer:

7 Xe-Cu bond lengths in XeCuCl  Experimental r m (2) (Xe-Cu) = (4) Å  MP2 results r(Xe-Cu) = Å a  van der Waals limit:  Covalent limit: a Lovallo, C. C.; Klobukowski, M. Chem. Phys. Lett. 2002, 368, 589. b Pyykkö, P. Chem. Rev. 1997, 97, 597. c Huheey, J. E. et al. Inorganic Chemistry, Principles of Structure and Reactivity, 4th Ed.; Harper-Collins: New York, d Bartlett, N et al. In Comprehensive Inorganic Chemistry; Bailar, J. C. et al. Eds.;Pergamon: Oxford, 1973; e Pyykkö, P. Chem. Rev. 1988, 88, 579. (r vdW (Xe) b + r ion (Cu + ) c ) = 2.78 Å (r cov (Xe) d + r cov (Cu(I)) e ) = 2.36 Å

8 Centrifugal Distortion Constants Small centrifugal distortion constants  Highly rigid molecules D J /kHz X 10 2 k(Ng-M) /Nm -1 XeCuF2094 XeAuF7137 ArAgCl3534 Ar-NaCl a a Mizoguchi, A.; Endo, Y.; Ohshima, Y. J. Chem. Phys. 1998, 109,

9 Nuclear Quadrupole Coupling Constants (MHz) for 131 Xe 131 Xe0 131 Xe-Ar a Xe-HCl b Xe 63 CuX-81.4 to Xe 107 AgX c to XeAuF d XeH + e Xe [Kr]5s 2 4d 10 5p 5 6s 1 f -505 a Xu, Y. et al. JCP, 1993, 99, 919. b Keenan, M. R. et al. JCP, 1980, 73(8), c Cooke, S.A. et al. PCCP, 2004, 6, d Cooke S.A. et al. JACS, 2004, 126, e Kellö, V. et al. Chem. Phys. Lett., 2001, 346, 155. f Faust, W. L. et al. Phys. Rev., 1961, 123, 198.

10 Ab initio calculations  A large dissociation energy was calculated for XeCuCl (55 kJ mol -1 );  Charge-induced dipole induction energy for XeCuCl: 21 kJ mol -1 ;  Mulliken and NBO populations show significant donation of electron density from the Xe to the Cu;  Donation of ~ of an elementary charge donated from Xe to Cu.

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12 MOLDEN plots of valence MOs

13 Local Energy Densities a H(r) = G(r) + V(r) Values are calculated at the bond critical point of the maximum electron density (MED) path between bonded atoms. Negative H(r) implies … V(r) dominates … e- density accumulates at r B … a covalent bond forms!! a Cremer, D.; Kraka, E. Angew. Chem. 1984, 96, 612; see also Angew. Chem. Int. Ed. Engl., 1984, 23, 627.

14 Local Energy Densities Local Energy Densities at r B (Hartree Å -3 ) for several NgMX molecules ArCuF ArCuCl KrCuF KrCuCl XeCuF XeCuCl XeAgF XeAgCl XeAuF ! All negative values

15 Conclusion  First preparation and characterization XeCuCl;  Very strong Xe-Cu interactions observed;  Strong Ng-M interactions similar to those expected from previous NgMX studies;  XeCuCl shows convincing evidence of covalent Xe-Cu bonding.

16 Acknowledgements Thank you to Mike Gerry, Steve Cooke and Christine Krumrey. This research has been supported by the Natural Sciences and Engineering Research Council (NSERC) of Canada. Thank you for your attention.