Transcript columbus 2005 Michaud2.ppt

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.
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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 transitions
in 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 transitions
in this one spectrum
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Representative Spectroscopic Constants
129Xe63Cu35Cl
131Xe63Cu35Cl
132Xe63Cu35Cl
Bo /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)
-
-81.4(2)
-
Parameter
eQq(131Xe) /MHz
Nuclear quadrupole coupling constants of the CuCl monomer:
eQq(63Cu) /MHz = 16.17
eQq(35Cl) /MHz = -32.1
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Xe-Cu bond lengths in XeCuCl
Experimental r m(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
Lovallo, C. C.; Klobukowski, M. Chem. Phys. Lett. 2002, 368, 589.
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.
a
b
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Centrifugal Distortion Constants
Small centrifugal distortion constants  Highly rigid molecules
DJ 
4 Bo3
1

2
2
k

XeCuF
DJ
/kHz X 102
20
k(Ng-M)
/Nm-1
94
XeAuF
7
137
ArAgCl
35
34
Ar-NaCla
900
0.6
8
a
Mizoguchi, A.; Endo, Y.; Ohshima, Y. J. Chem. Phys. 1998, 109, 10539.
Nuclear Quadrupole Coupling Constants
(MHz) for 131Xe
131Xe
a Xu,
131Xe
0
131Xe-Ara
0.723
131Xe-HClb
-4.9
131Xe63CuX
-81.4 to -87.8
131Xe107AgXc
-78.1 to -82.8
131XeAuFd
-134.5
131XeH+ e
-369.5
[Kr]5s24d105p56s1 f
-505
b Keenan, M. R. et al. JCP, 1980, 73(8), 3523.
Y. et al. JCP, 1993, 99, 919.
c Cooke, S.A. et al. PCCP, 2004, 6, 3248. d Cooke S.A. et al. JACS, 2004, 126, 17000.
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e Kellö, V. et al. Chem. Phys. Lett., 2001, 346, 155. f Faust, 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.
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Plots of dissociation energy vs. force constant for
all studied NgMX molecules
From the
Morse Potential:
k = 2Deâ2
Dissociation Energy, De (kJ/mol)
100
80
XeAuF
KrAuF
XeCuF
60
XeCuCl
XeAgF
KrAgF
KrAgCl
ArAgF
20
KrCuF
ArAuF
KrCuCl
ArAuCl
ArCuF
XeAgCl
40
KrAuCl
ArMX
KrMX
XeMX
ArCuCl
ArMX
KrMX
ArAgCl
XeMX
0
20
40
60
80
100
Force constant, k (N/m)
120
140
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MOLDEN plots of valence MOs
Xe
Cu
Cl
3σ
1π
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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 Densities
Local Energy Densities at rB (Hartree Å-3)
for several NgMX molecules
ArCuF
-0.0151
ArCuCl
-0.0148
KrCuF
-0.0400
KrCuCl
-0.0390
XeCuF
-0.0699
XeCuCl
-0.0667
XeAgF
-0.0542
XeAgCl
-0.0457
XeAuF
-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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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.
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