Synthesis and characterization of a pyrazolium bearing N-heterocyclic carbene-palladium(II) complex

Article abstract of DOI:10.1016/j.jorganchem.2012.11.021

3,5-Dichloro-1,2-diphenylpyrazolium tetrafluoroborate 1 reacts at 0 °C with 2,6-dimethylphenol in the presence of triethylamine to give the 5-chloro-3-aryloxy-1,2-diphenylpyrazolium tetrafluoroborate 2 (58% yield). Heterocycle 2 reacts with 1-methylimidazole affording 5-(1-methyl-1H- imidazolium-3-yl)-3-aryloxy-1,2-diphenylpyrazolium chloride tetrafluoroborate 3 in 83% yield. When half an equivalent of allylchloropalladium dimer [Pd(allyl)Cl]₂ is added to 3 in the presence of triethylamine, monocationic compound 4 featuring an N-heterocyclic carbene coordinated to allylchloropalladium(II) is isolated in 72% yield. All compounds have been fully characterized by multinuclear NMR spectroscopy. We also describe the X-ray crystal structure of 4, which crystallizes in the monoclinic C2/c space group.

Full text of DOI:10.1016/j.jorganchem.2012.11.021

Journal of Organometallic Chemistry 724 (2013) 251e254
Contents lists available at SciVerse ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis and characterization of a pyrazolium bearing N-heterocyclic carbenee
palladium(II) complex
,
Emrah Giziroglu a, Bruno Donnadieu b, Guy Bertrand b
*
a Department of Chemistry, Faculty of Arts and Sciences, Adnan Menderes University, 09100 Aydın, Turkey
b UCSD-CNRS Joint Research Chemistry Laboratory (UMI 3555), Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA 92093-0343, USA
a r t i c l e i n f o
a b s t r a c t
3,5-Dichloro-1,2-diphenylpyrazolium tetrafluoroborate 1 reacts at 0 ꢀC with 2,6-dimethylphenol in the
presence of triethylamine to give the 5-chloro-3-aryloxy-1,2-diphenylpyrazolium tetrafluoroborate 2
(58% yield). Heterocycle 2 reacts with 1-methylimidazole affording 5-(1-methyl-1H-imidazolium-3-yl)-
3-aryloxy-1,2-diphenylpyrazolium chloride tetrafluoroborate 3 in 83% yield. When half an equivalent of
allylchloropalladium dimer [Pd(allyl)Cl]2 is added to 3 in the presence of triethylamine, monocationic
compound 4 featuring an N-heterocyclic carbene coordinated to allylchloropalladium(II) is isolated in
72% yield. All compounds have been fully characterized by multinuclear NMR spectroscopy. We also
describe the X-ray crystal structure of 4, which crystallizes in the monoclinic C2/c space group.
Ó 2012 Elsevier B.V. All rights reserved.
Article history:
Received 8 October 2012
Received in revised form
8 November 2012
Accepted 16 November 2012
Keywords:
N-Heterocyclic carbene
Pyrazolium
Bent-allene
Palladium(II) complex
1. Introduction
Reaction of salt 1 with one equivalent of 2,6-dimethylphenol at
room temperature, in presence of excess triethylamine as a base,
Carbenes are neutral compounds featuring a divalent carbon
atom with only six electrons in its valence shell [1]. Following the
synthesis of the first stable phosphanyl(silyl)carbene in 1988 by our
group [2], Arduengoreported the first structurallycharacterized free
imidazol-2-ylidene (NHC) in 1991 [3]. NHCs are excellent ligands for
transition metals and the corresponding complexes proved to be
efficient catalysts for many organic reactions such as the Heck,
Kumada, Stille, SuzukieMiyaura, and Sonogashira coupling reac-
tions, amination reactions, hydrosilylation, olefin metathesis,
hydroformylation, polymerization, transfer hydrogenation etc [4].
Recently, another type of carbon-based ligand has been isolated.
Named bent-allenes [5] or carbodicarbenes [6], they are not only
cleanly gave 2 as indicated by 13C and 1H NMR spectroscopy.
Indeed, in the 13C NMR (in CD3CN) spectrum, the CH carbon of the
pyrazolium ring appeared at 92.5 ppm, and the 1H NMR (in CDCl3)
spectrum showed the pyrazolium ring proton at 5.94 ppm.
In the next step, 2 was treated with N-methyl imidazole at
room temperature. 13C NMR spectroscopy of the reaction mixture
revealed clean substitution, as shown by the CH carbon signal of
the pyrazolium ring, which was slightly shifted from 92.5 to
92.3 ppm. Also distinctive, the signal of the CH carbon of the
imidazolium group, which appears at 133.8 ppm. After workup,
and recrystallization from
a saturated acetonitrile solution
at ꢁ30 ꢀC, dicationic salt 3 was obtained as non-hygroscopic
colorless crystals (83% yield). Unfortunately, deprotonation of
the dicationic salt 3 with two equivalents of various bases (LDA,
KHMDS, KOtBu, MesLi, and nBuLi) did not produce the desired
free cyclic allene bearing an N-heterocyclic carbene (30) (Scheme
2), but a complex mixture.
stronger
s-donors but also less p-acceptor ligands than NHCs:
consequently they are promising ligands for transition metals [7].
While searching for novel and effective ligands for new catalytic
reactions, we chose to target heteroditopic ligands [8], featuring
a bent-allene and an NHC, and herewe reportour preliminaryresults.
Although the initial goal to isolate the free cyclic allene bearing
a metal-free NHC could not be achieved, reaction of 3 with half an
equivalent of allylchloropalladium dimer [Pd(allyl)Cl]2 and trie-
thylamine in acetonitrile afforded cleanly the pyrazolium
substituted NHCePd(II) complex 4 (Scheme 2). The 13C NMR
spectrum (in CDC13) showed the carbene signal at 184 ppm, which
falls in the typical range for transition metaleNHC complexes [10].
The 1H NMR spectrum revealed the disappearance of the
2. Result and discussion
The synthesis started from the readily available 3,5-dichloro-
1,2-diphenylpyrazolium tetrafluoroborate
1 [9] (Scheme 1).
* Corresponding author. Tel.: þ1 858 534 5412.
E-mail address: guybertrand@ucsd.edu (G. Bertrand).
0022-328X/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2012.11.021

252
E. Giziroglu et al. / Journal of Organometallic Chemistry 724 (2013) 251e254
N
N
BF4, Cl
N
N
N
N
BF4
Cl
Ar-OH, NEt3
N
N
N
BF4
Cl
O
O
Cl
N
H
H
H
H
2
3
1
Ar: 2,6-dimethylphenyl
Scheme 1. Synthesis of compounds 2 and 3.
imidazolium CH proton and the region of the allyl moiety displayed
a very characteristic pattern that indicates the coordination of the
carbene to the palladium center (1 multiplet and 4 doublets) [11].
The ionic structure of 4 was indicated by its very low solubility in
nonpolar solvents and by the presence of a sharp signal at ꢁ1.2
(CDC13) in the 11B NMR spectrum, due to the tetrafluoroborate
anion. Colorless crystals of 4 suitable for an X-ray diffraction study
were obtained by slow evaporation of a chloroform solution at
room temperature. The structure of 4 is illustrated in Fig. 1, and
selected bond lengths and angles are given in Table 1.
experimental details along with the final parameters are
summarized in Table 2.
All attempts to deprotonate the pyrazolium ring of the mono-
cationic NHCePd(II) complex 4 with mild or strong bases failed to
give the desired palladium complex 40 featuring the heteroditopic
cyclic bent alleneeNHC ligand. This is a further demonstration of
the extreme basicity of cyclic bent-allenes [5].
3. Conclusion
The single crystal X-ray diffraction analysis unambiguously
demonstrates the monocationic nature of 4. The palladium atom is
coordinated in a slightly distorted square planar geometry with
In conclusion, a novel pyrazolium bearing an N-heterocyclic
carbene palladium(II) complex was synthesized and characterized
by various spectroscopic techniques, and by a single crystal X-ray
diffraction study. Unfortunately, all attempts to synthesize the free
chelating ligand featuring both an N-heterocyclic carbene and
a cyclic bent-allene failed. However, this work shows that the
pyrazolium bearing an imidazol-2-ylidene Pd(II) complex is stable
at room temperature even in air and water. The modifications of the
the allyl moiety h
3-coordinated to the metal center. All the data for
the allylpalladium complex 4 are comparable to those reported for
others NHCePd(II) complexes [12]. The PdeCcarbene, PdeCl and
ꢀ
ꢀ
ꢀ
N2eC4 bond distance are 2.039(3) A, 2.383(7) A and 1.389(3) A,
while the C1ePd1eC31, C1ePd1eC29 and C29ePd1eCl1 angles
are 98.29(13), 167.22(14) and 97.55(12), respectively. The internal
angles of the heterocycles are 103.7(2) for N1eC1eN2 and
104.8(2) for C4eC5eC6. The relevant crystal data and
BF4, Cl
N
N
N
N
N
N
O
O
N
N
H
H
3'
3
Pd
, Et N
1/2 Cl
Cl
3
Pd
BF4
N
N
N
N
N
BF4
N
O
O
N
N
H
Cl
Pd
Pd
4'
4
Fig. 1. Molecular structure of 4 in the solid state (hydrogen atoms are omitted for
Scheme 2. Synthesis of complex 4.
clarity; ellipsoids are drawn at 30% probability).

E. Giziroglu et al. / Journal of Organometallic Chemistry 724 (2013) 251e254
253
Table 1
Fourier maps. Atomic coordinates, isotropic and anisotropic
displacement parameters of all the non-hydrogen atoms of the
compound were refined by means of a full matrix least-squares
procedure on F2. Drawings of the molecule were performed using
Ortep 3.
Selected bond lengths (Å) and angles (deg) with esd’s in parentheses, for complex 4.
Pd(1)eC(1)
Pd(1)eCl(1)
Pd(1)eC(29)
Pd(1)eC(30)
2.039(3)
2.383(7)
2.166(3)
2.120(4)
1.381(4)
95.12(7)
98.29(13)
103.7(2)
126.82(18)
167.22(14)
Pd(1)eC(31)
N(2)eC(4)
O(1)eC(6)
N(1)eC(1)
2.110(3)
1.389(3)
1.335(3)
1.331(3)
1.386(3)
129.23(19)
104.8(2)
132.4(2)
121.5(2)
97.55(12)
N(1)eC(2)
N(3)eN(4)
C(1)ePd(1)eCl(1)
C(1)ePd(1)eC(31)
N(1)eC(1)eN(2)
N(2)eC(1)ePd(1)
C(1)ePd(1)eC(29)
N(1)eC(1)ePd(1)
C(6)eC(5)eC(4)
O(1)eC(6)eC(5)
N(3)eC(4)eN(2)
C(29)ePd(1)eCl(1)
4.2. 5-Chloro-3-phenoxy-1,2-diphenylpyrazolium tetrafluoroborate 2
2,6-Dimethylphenol (1.86 g, 13.2 mmol) and triethylamine
(33 mL, 23.5 mmol) were added at 0 ꢀC to an acetonitrile (50 mL)
solution of 3,5-dichloro-1,2-diphenylpyrazolium tetrafluoroborate
1 (5.0 g, 13.2 mmol). After stirring for 6 h at 0 ꢀC, the reaction
mixture was concentrated to 1/2 of its original volume and then
diethyl ether (250 mL) was added to precipitate the product and
ammonium salts. After filtration, the solid residue was washed with
water (5 ꢂ 150 mL), and then with diethyl ether (3 ꢂ 40 mL). After
recrystallization from ethanol, 2 was obtained as a colorless solid
substituents on the pyrazolium and imidazolium rings and the
possibility of introducing a spacer between the pyrazolium and
imidazolium groups are under active investigation.
(3.55 g, 58%). m.p.: 138e141 ꢀC; 1H NMR (300 MHz, CDCl3):
(s, 6H), 5.94 (s, 1H), 7.16e7.17 (m, 3H), 7.47e7.51 (m, 6H), 7.69e7.72
(m, 4H) ppm; 13C NMR (75 MHz, CD3CN):
¼ 15.3, 92.5,127.8,128.0,
128.4, 129.4, 129.8, 130.2, 130.4, 132.1, 132.8, 133.3, 140.6, 150.1,
156.8 ppm; 11B NMR (96 MHz, CDCl3):
¼ ꢁ1.3 ppm.
d
¼ 2.34
4. Experimental
d
4.1. General
d
All manipulations and reactions were performed under a puri-
fied argon atmosphere using standard Schlenk techniques. Dry,
oxygen-free solvents were employed. Commercially available
reagents were used without further purification. 3,5-Dichloro-1,2-
diphenylpyrazolium tetrafluoroborate 1 was prepared according
to the reported procedures [9]. Melting points were measured with
an Electro thermal 9200 melting point apparatus and the values are
uncorrected. 1H, 13C and 11B NMR spectra were recorded on a Bruker
Avance 300 spectrometer. Chemical shifts are reported in ppm
downfield from Me4Si and were referenced to solvent peaks. X-ray
measurements were recorded on the Bruker X8-APEX [13] X-ray
diffraction instrument with Mo-radiation. All data frames were
4.3. 5-(1-Methyl-1H-imidazol-3-ium-3-yl)-3-phenoxy-1,
2-diphenylpyrazolium chloride tetrafluoroborate 3
1-Methylimidazole (0.45 g, 5.4 mmol) was added to a 5:1 CHCl3/
CH3CN solution (25 mL) of 2 (2.5 g, 5.4 mmol) at room temperature.
The solution was heated and stirred at 60 ꢀC for 6 h. The reaction
mixture was concentrated to 1/2 of its original volume and then
diethyl ether (250 mL) was added to precipitate the product. After
filtration, the solid residue was washed with diethyl ether, recrys-
tallized from a saturated acetonitrile solution at ꢁ30 ꢀC, and dried
under vacuum to give 3 as colorless crystals (2.43 g, 83%). m.p.:
collected at low temperatures (T ¼ 100 K) using an
u, 4-scan mode
(0.3ꢀ
u
-scan width, hemisphere of reflections) and integrated using
167 ꢀC (dec); 1H NMR (300 MHz, CDCl3):
d
¼ 2.38 (s, 6H), 3.90 (s,
a Bruker SAINTPLUS software package [14]. The intensity data were
corrected for lorentzian polarization. Absorption corrections were
performed using the SADABS program [15]. The SIR97 [16] software
was used for direct methods solution and phase determination, and
Bruker SHELXTL [17] for structure refinement and difference
3H), 6.22 (s, 1H), 7.08e7.10 (m, 3H), 7.30e7.49 (m, 8H), 7.88 (d,
JHH ¼ 6.6 Hz, 2H), 8.19 (d, JHH ¼ 7.34 Hz, 2H), 10.37 (s, 1H) ppm; 13
C
NMR (75 MHz, CD3CN):
d
¼ 16.2, 37.7, 92.3,124.2,125.7,128.9,129.6,
129.8, 130.4, 130.6, 130.9, 131.1, 131.2, 133.8, 133.9, 140.4, 151.0,
157.3 ppm; 11B NMR (96 MHz, CDCl3):
d
¼ ꢁ1.3 ppm.
Table 2
4.4. Allylchloro{1-[3-(2,6-dimethylphenoxy)-1,
2-diphenylpyrazoliumyl]-3-methyl-imidazol-2-ylidene}
palladium(II) tetrafluoroborate 4
Crystal data and structure refinement for complex 4.
Empirical formula
C30H30BClF4N4OPd
Formula weight
Temperature
Wavelength
691.24
100(2) K
0.71073 A
Monoclinic
C2/c
37.0409(7)
11.0088(2)
16.9809(3)
A mixture of [Pd(allyl)Cl]2 (0.23 g, 0.6 mmol), dicationic salt 3
(0.65 g, 1.2 mmol), and Et3N (0.22 mL, 1.6 mmol), was dissolved in
CH3CN (20 mL) and the solution was stirred at room temperature
for 2 h. After evaporation of the solvent the crude residue was
washed with water (2 ꢂ 20 mL). Then the organic layer was
extracted with CH2Cl2 (20 mL) and dried over anhydrous MgSO4.
After removal of the solvent under vacuum, 4 was obtained as
a white solid (0.29 g, 72%). Crystals [m.p.: 205 ꢀC (dec)] suitable for
X-ray crystallography were obtained by slow evaporation of
a chloroform solution of complex 4. 1H NMR (300 MHz, CDCl3):
ꢀ
Crystal system
Space group
ꢀ
a, A
ꢀ
b, A
ꢀ
c, A
a
, deg
, deg
90
b
105.7390(10)
90
6664.8(2)
8
1.378
0.687
30,293
5662
g
, deg
3
ꢀ
V, A
Z
d calc Mg mꢁ3
d
¼ 2.32 (d, JHH ¼ 13.6 Hz, 1H), 2.39 (s, 6H), 3.14 (d, JHH ¼ 13.6 Hz,
m
, mmꢁ1
1H), 3.56 (d, JHH ¼ 6.6 Hz, 1H), 3.71 (s, 3H), 4.22 (d, JHH ¼ 6.6 Hz, 1H),
5.03 (m, 1H), 5.98 (s, 1H), 7.11 (s, 2H), 7.27e7.34 (m, 5H), 7.43e7.60
(m, 4H), 7.74 (d, JHH ¼ 7.34 Hz, 2H), 8.02 (d, JHH ¼ 7.34 Hz, 2H) ppm;
Reflections collected
Nmeasd
[Rint
]
[0.0233]
13C NMR (75 MHz, CDCl3):
d
¼ 15.9, 38.5, 50.8, 72.4, 90.26, 114.9,
Final R indices [I > 2
R indices (all data)
GOF
s
(I)]
R1 ¼ 0.0319, wR2 ¼ 0.0830
R1 ¼ 0.0357, wR2 ¼ 0.0858
1.064
0.948, ꢁ0.655
122.9, 123.3, 127.6, 129.1, 129.3, 129.4, 129.6, 129.8, 130.5, 131.8,
132.2, 144.9, 150.3, 156.0, 184.0 (Ccarbene) ppm; 11B NMR (96 MHz,
ꢀꢁ3
Largest diff. peak and hole [e A
]
CDCl3):
d
¼ ꢁ1.2 ppm.

254
E. Giziroglu et al. / Journal of Organometallic Chemistry 724 (2013) 251e254
[6] (a) R. Tonner, G. Frenking, Angew. Chem. Int. Ed. 46 (2007) 8695e8698;
Acknowledgments
(b) N. Takagi, T. Shimizu, G. Frenking, Chem. Eur. J. 15 (2009) 8593e8604;
(c) G. Frenking, R. Tonner, Pure Appl. Chem. 81 (2009) 597e614;
(d) N. Takagi, T. Shimizu, G. Frenking, Chem. Eur. J. 15 (2009) 3448e3456;
(e) R. Tonner, G. Frenking, Chem. Eur. J. 14 (2008) 3273e3289;
(f) A. Fürstner, M. Alcarazo, R. Goddard, C.W. Lehmann, Angew. Chem. Int. Ed.
47 (2008) 3210e3214;
We are grateful to the NSF Foundation (CHE-1112133) for
financial support of this work, and to the Scientific and Techno-
logical Research Council of Turkey (TÜBITAK) for a graduate
fellowship (E.G.).
_
(g) M. Alcarazo, C.W. Lehmann, A. Anoop, W. Thiel, A. Fürstner, Nat. Chem. 1
(2009) 295e301;
(h) O. Kaufhold, F.E. Hahn, Angew. Chem. Int. Ed. 47 (2008) 4057e4061.
[7] For reviews on bent-allenes/carbodicarbenes, see: (a) M. Albrecht, Chem.
Commun. (2008) 3601e3610;
Appendix A. Supplementary material
(b) O. Schuster, L. Yang, H.G. Raubenheimer, M. Albrecht, Chem. Rev. 109
(2009) 3445e3478;
(c) M. Albrecht, Chimia 63 (2009) 105e110;
(d) M. Melaimi, M. Soleilhavoup, G. Bertrand, Angew. Chem. Int. Ed. 49 (2010)
8810e8849;
(e) D. Martin, M. Melaimi, M. Soleilhavoup, G. Bertrand, Organometallics 30
(2011) 5304e5313.
CCDC 882110 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
References
[8] For reviews on heteroditopic ligands, see: (a) P. Braunstein, F. Naud, Angew.
Chem. Int. Ed. 40 (2001) 680e699;
(b) C.S. Slone, D.A. Weimberger, C.A. Mirkin, Prog. Inorg. Chem. 48 (1999)
233e250;
(c) E.C. Constable, P. Haverson, C.E. Housecroft, E. Nordlander, J. Olsson,
Polyhedron 25 (2006) 437e458.
[1] (a) R.A. Moss, M.S. Platz, M. Jones Jr., Reactive Intermediate Chemistry, Wiley-
Interscience, Hoboken, New Jersey, 2004;
(b) D. Bourissou, O. Guerret, F.P. Gabbai, G. Bertrand, Chem. Rev. 100 (2000)
39e91.
[9] A.I. Eid, M.A. Kira, H.H. Fahmy, J. Pharm. Belg. 33 (1978) 303e311.
[10] (a) D. Tapu, D.A. Dixon, C. Roe, Chem. Rev. 109 (2009) 3385e3407;
(b) D.E. Bergbreiter, H.L. Su, H. Koizumi, J. Tian, J. Organomet. Chem. 696
(2011) 1272e1279.
[11] C. Fliedel, A.M. François, S. Bellemin-Laponnaz, Inorg. Chim. Acta 360 (2007)
143e148.
[2] (a) A. Igau, H. Grützmacher, A. Baceiredo, G. Bertrand, J. Am. Chem. Soc. 110
(1988) 6463e6466;
(b) A. Igau, A. Baceiredo, G. Trinquier, G. Bertrand, Angew. Chem. Int. Ed. Engl.
28 (1989) 621e622.
[3] A.J. Arduengo III, R.L. Harlow, M. Kline, J. Am. Chem. Soc. 113 (1991) 361e363.
[4] For recent reviews, see: (a) S. Díez-González (Ed.), N-Heterocyclic Carbenes,
from Laboratory Curiosities to Efficient Synthetic Tool, Royal Society of
Chemistry Publishing, Cambridge, 2011;
[12] (a) O. Winkelmann, C. Näther, U. Lüning, J. Organomet. Chem. 693 (2008)
2784e2788;
(b) H. Clavier, A. Correa, L. Cavallo, E.C. Escudero-Adán, J. Benet-Buchholz,
A.M.Z. Slawin, S.P. Nolan, Eur. J. Inorg. Chem. 27 (2009) 1767e1773.
[13] Bruker, APEX 2 Version 5.1, Bruker AXS Inc., Madison, Wisconsin, U.S.A, 2009.
[14] Bruker, SAINT Version V7.60A, Bruker AXS Inc., Madison, Wisconsin, U.S.A,
2009.
[15] Bruker, SADABS, Version 2008/1, Bruker Analytical X-Ray System, Inc., Mad-
ison, Wisconsin, U.S.A, 2008.
[16] A. Altomare, M.C. Burla, M. Carnalli, M. Carascano, G. Giacovazzo,
C. Guagliardi, A.G.G. Moliterni, G. Polidori, G.R. Spagan, J. Appl. Crystallogr. 32
(1997) 115e119.
(b) T. Droege, F. Glorius, Angew. Chem. Int. Ed. 49 (2010) 6940e6952;
(c) F.E. Hahn, M.C. Jahnke, Angew. Chem. Int. Ed. 47 (2008) 3122e3172;
(d) G.C. Vougioukalakis, R.H. Grubbs, Chem. Rev. 110 (2010) 1746e1787;
(e) S. Díez-González, N. Marion, S.P. Nolan, Chem. Rev. 109 (2009) 3612e
3676;
(f) A. Grossmann, D. Enders, Angew. Chem. Int. Ed. 51 (2012) 314e325.
[5] (a) C.A. Dyker, V. Lavallo, B. Donnadieu, G. Bertrand, Angew. Chem. Int. Ed. 47
(2008) 3206e3209;
(b) V. Lavallo, C.A. Dyker, B. Donnadieu, G. Bertrand, Angew. Chem. Int. Ed. 47
(2008) 5411e5414;
(c) M. Melaimi, P. Parameswaran, B. Donnadieu, G. Frenking, G. Bertrand,
Angew. Chem. Int. Ed. 48 (2009) 4792e4795.
[17] Bruker, SHELXTL Software Version 6.14, Bruker Analytical X-Ray System, Inc.,
Madison, Wisconsin, U.S.A, Dec 2003.