The Study of Noble Gas – Noble Metal Halide Interactions: Fourier Transform Microwave Spectroscopy of XeCuCl

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

June 2005International Symposium on Molecular

Spectroscopy

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XeCuClAnticipated 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.

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The Experiment

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132Xe63Cu35Cl Spectrum

Natural abundance:14.1%

I(63Cu) = 3/2

I(35Cl) = 3/2

Total of 10 transitionsin this one spectrum

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131Xe63Cu35Cl Spectrum

Natural abundance: 11.1%

I(131Xe) = 3/2

I(63Cu) = 3/2

I(35Cl) = 3/2

Total of 15 transitionsin this one spectrum

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Representative Spectroscopic Constants

Parameter 129Xe63Cu35Cl 131Xe63Cu35Cl 132Xe63Cu35ClBo /MHz 757.30669(9) 753.0300(2) 750.93467(5)

DJ /kHz 0.0794(7) 0.104(2) 0.0782(4)

eQq(Cu) /MHz 41.81(9) 41.6(1) 41.57(6)

eQq(Cl) /MHz -26.10(6) -26.4(1) -26.01(4)

eQq(131Xe) /MHz - -81.4(2) -

eQq(63Cu) /MHz = 16.17 eQq(35Cl) /MHz = -32.1

Nuclear quadrupole coupling constants of the CuCl monomer:

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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:

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.

(rvdW(Xe)b + rion(Cu+)c) = 2.78 Å

(rcov(Xe)d + rcov(Cu(I))e) = 2.36 Å

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Centrifugal Distortion Constants

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oJ

BD

k21

Small centrifugal distortion constants Highly rigid molecules

DJ

/kHz X 102 k(Ng-M)

/Nm-1

XeCuF 20 94XeAuF 7 137ArAgCl 35 34

Ar-NaCla 900 0.6a Mizoguchi, A.; Endo, Y.; Ohshima, Y. J. Chem. Phys. 1998, 109, 10539.

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Nuclear Quadrupole Coupling Constants (MHz) for 131Xe

131Xe 0131Xe-Ara 0.723

131Xe-HClb -4.9131Xe63CuX -81.4 to -87.8

131Xe107AgXc -78.1 to -82.8131XeAuFd -134.5131XeH+ e -369.5

131Xe [Kr]5s24d105p56s1 f -505

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. f Faust, W. L. et al. Phys. Rev., 1961, 123, 198.

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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.

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0

20

40

60

80

100

20 40 60 80 100 120 140

Force constant, k (N/m)

Dis

soci

atio

nE

nerg

y,D

e(k

J/m

ol)

ArMX

KrMX

XeMX

ArMX

KrMX

XeMXArAgClArAgF

KrAgClKrAgF

XeAgClXeAgF

ArCuCl

KrCuClArAuCl

ArCuF

KrCuF

KrAuCl

KrAuF

ArAuF

XeAuF

XeCuClXeCuF

From the Morse Potential:k = 2D âe

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Plots of dissociation energy vs. force constant for all studied NgMX molecules

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MOLDEN plots of valence MOs

X e

C u

C l

3 σ 1 π

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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.

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Local Energy DensitiesLocal Energy Densities at rB

(Hartree Å-3) for several NgMX molecules

ArCuF -0.0151ArCuCl -0.0148KrCuF -0.0400KrCuCl -0.0390XeCuF -0.0699XeCuCl -0.0667

XeAgF -0.0542XeAgCl -0.0457XeAuF -0.1799

!All negative values

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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.

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AcknowledgementsThank 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.