Julie M. Michaud and Michael C. L. Gerry University of British Columbia, Vancouver, BC Canada

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

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

The Experiment

132Xe63Cu35Cl Spectrum Natural abundance: 14.1% I(63Cu) = 3/2 I(35Cl) = 3/2 Total of 10 transitions in this one spectrum

131Xe63Cu35Cl Spectrum Natural abundance: 11.1% I(131Xe) = 3/2 I(63Cu) = 3/2 I(35Cl) = 3/2 Total of 15 transitions in this one spectrum

Representative Spectroscopic Constants Nuclear quadrupole coupling constants of the CuCl monomer:

Xe-Cu bond lengths in XeCuCl • Experimental rm(2)(Xe-Cu) = 2.4669(4) Å • MP2 results r(Xe-Cu) = 2.497 Å a • van der Waals limit: • Covalent limit: (rvdW(Xe)b + rion(Cu+)c) = 2.78 Å (rcov(Xe)d + rcov(Cu(I))e) = 2.36 Å 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, 1993. d Bartlett, N et al. In Comprehensive Inorganic Chemistry; Bailar, J. C. et al. Eds.;Pergamon: Oxford, 1973; 213-330. e Pyykkö, P. Chem. Rev.1988, 88, 579.

Centrifugal Distortion Constants Small centrifugal distortion constants  Highly rigid molecules a Mizoguchi, A.; Endo, Y.; Ohshima, Y. J. Chem. Phys. 1998, 109, 10539.

Nuclear Quadrupole Coupling Constants (MHz) for 131Xe a Xu, Y. et al. JCP, 1993, 99, 919. b Keenan, M. R. et al. JCP, 1980, 73(8), 3523. c Cooke, S.A. et al. PCCP, 2004, 6, 3248. d Cooke S.A. et al. JACS, 2004, 126, 17000. e Kellö, V. et al. Chem. Phys. Lett., 2001, 346, 155. fFaust, W. L. et al. Phys. Rev., 1961, 123, 198.

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 ~0.1-0.2 of an elementary charge donated from Xe to Cu.

MOLDEN plots of valence MOs

Local Energy Densitiesa 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 rB … a covalent bond forms!! a Cremer, D.; Kraka, E. Angew. Chem. 1984, 96, 612; see also Angew. Chem.Int. Ed. Engl., 1984, 23, 627.

Local Energy Densities !All negative values

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.

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.

Julie M. Michaud and Michael C. L. Gerry University of British Columbia, Vancouver, BC Canada