Trinuclear silver(I) complexes of fluorinated pyrazolates

Article abstract of DOI:10.1021/ic062374k

Silver pyrazolates {[3-(CF₃)Pz]Ag}₃, {[3-(CF ₃),5-(CH₃)Pz]Ag}₃, {[3-(CF₃),5-(Ph) Pz]Ag}₃, {[3-(CF₃),5-(Bu^t)Pz]Ag}₃, and {[3-(C₃F₇),5-(Bu^t)Pz]Ag}₃ have been synthesized by treatment of the corresponding pyrazole with a slight molar excess of silver(I) oxide. This economical and convenient route gives silver pyrazolates in high (>80%) yields. X-ray crystal structures of {[3-(CF ₃),5-(CH₃)Pz]Ag}₃, {[3-(CF₃),5- (Bu^t)Pz]Ag}₃, and {[3-(C₃F₇),5- (Bu^t)Pz]-Ag}₃ show that these molecules have trinuclear structures with essentially planar to highly distorted Ag₃N ₆ metallacycles. {[3-(CF₃),5-(CH₃)Pz]Ag} ₃ forms extended columns via intertrimer argentophilic contacts (the closest Ag...Ag separation between the neighboring trimers are 3.355 and 3.426 A). The trinuclear {[3-(CF₃),5-(Bu^t)Pz]Ag} ₃ units crystallize in pairs, basically forming dimers of trimers , with the six silver atom core of the adjacent trimers adopting a chair conformation. However, in these dimers of trimers, even the shortest intertrimer Ag...Ag distance (3.480 A) is slightly longer than the van der Waals contact of silver (3.44 A). {[3-(C₃F ₇),5-(Bu^t)Pz]Ag}₃, which has two bulky groups on each pyrazolyl ring, shows no close intertrimer Ag...Ag contacts (closest intertrimer Ag...Ag distance = 5.376 A). The Ag-N bond distances and the intratrimer Ag-Ag separations of the silver pyrazolates do not show much variation. However, their N-Ag-N angles are sensitive to the nature (especially, the size) of substituents on the pyrazolyl rings. The π-acidic {[3,5-(CF₃)₂Pz]Ag}₃ and {[3-(C ₃F₇),5-(Bu^t)Pz]Ag}₃ form adducts with the π-base toluene. X-ray data show that they adopt extended columnar structures of the type {[Ag₃]₂·[toluene]} _∞ and {[Ag₃]′·[toluene]} _∞ ({[3,5-(CF₃)₂Pz]Ag}₃ = [Ag₃],{[3-(C₃F₇),5-(Bu^t)Pz]Ag} ₃ = [Ag₃]′), in which toluene interleaves and makes face-to-face contacts with {[3-(C₃F₇),5-(Bu ^t)Pz]Ag}₃ or dimers of {[3,5-(CF₃) ₂Pz]Ag)₃.

Full text of DOI:10.1021/ic062374k

Inorg. Chem. 2007, 46, 2979−2987
Trinuclear Silver(I) Complexes of Fluorinated Pyrazolates
H. V. Rasika Dias,* Chammi S. Palehepitiya Gamage, Jeremy Keltner, Himashinie V. K. Diyabalanage,
Ivan Omari, Yvonne Eyobo, Nadeeka R. Dias, Nathan Roehr, Lesly McKinney, and Theresa Poth
Department of Chemistry and Biochemistry, The UniVersity of Texas at Arlington,
Arlington, Texas 76019
Received December 12, 2006
Silver pyrazolates
and
[3-(C3F7),5-(But)Pz]Ag
molar excess of silver(I) oxide. This economical and convenient route gives silver pyrazolates in high (>80%)
yields. X-ray crystal structures of [3-(CF3),5-(CH3)Pz]Ag 3, and
[3-(CF3),5-(But)Pz]Ag [3-(C3F7),5-(But)Pz]-
Ag show that these molecules have trinuclear structures with essentially planar to highly distorted Ag3N6
{[3-(CF3)Pz]Ag} , {[3-(CF3),5-(CH3)Pz]Ag} , {[3-(CF3),5-(Ph)Pz]Ag} , { } ,
[3-(CF3),5-(But)Pz]Ag
3 3 3 3
{
} have been synthesized by treatment of the corresponding pyrazole with a slight
3
{
}
,
3
{
}
{
}
3
metallacycles.
Ag‚‚‚Ag separation between the neighboring trimers are 3.355 and 3.426 Å). The trinuclear
Ag units crystallize in pairs, basically forming “dimers of trimers”, with the six silver atom core of the adjacent
{[3-(CF3),5-(CH3)Pz]Ag} forms extended columns via intertrimer argentophilic contacts (the closest
3
{
[3-(CF3),5-(But)Pz]-
}
3
trimers adopting a chair conformation. However, in these dimers of trimers, even the shortest intertrimer Ag‚‚‚Ag
distance (3.480 Å) is slightly longer than the van der Waals contact of silver (3.44 Å).
[3-(C3F7),5-(But)Pz]Ag
which has two bulky groups on each pyrazolyl ring, shows no close intertrimer Ag‚‚‚Ag contacts (closest intertrimer
Ag‚‚‚Ag distance 5.376 Å). The Ag N bond distances and the intratrimer Ag‚‚‚Ag separations of the silver
pyrazolates do not show much variation. However, their N Ag N angles are sensitive to the nature (especially, the
size) of substituents on the pyrazolyl rings. The -acidic [3,5-(CF3)2Pz]Ag and form
[3-(C3F7),5-(But)Pz]Ag
-base toluene. X-ray data show that they adopt extended columnar structures of the type
and [Ag3]′‚[toluene] [3,5-(CF3)2Pz]Ag}3 ) [Ag3], ), in
[3-(C3F7),5-(But)Pz]Ag}3 ) [Ag3]
[3-(C3F7),5-(But)Pz]Ag
or dimers of [3,5-(CF3)2-
{
} ,
3
)
−
−
−
π
{
}
{
}
3
3
adducts with the
[Ag3]2 [toluene]
π
{
‚
}
{
}
({
∞
{
′
∞
which toluene interleaves and makes face-to-face contacts with
Pz]Ag
{
}
3
{
}
.
3
Introduction
membered M3N6 metallacycles and often show various types
and degrees of intertrimer M‚‚‚M contacts leading to
supramolecular assemblies with chair, prismatic, and star-
shaped dimers of trimers or chain structures.21,23,38,39 Apart
from the interests related to structural diversity, some of these
coinage metal pyrazolates have been used for the examination
of metallophilic interactions between closed-shell d10 metal
Trinuclear pyrazolate complexes of monovalent coinage
metals (i.e., Cu(I), Ag(I), and Au(I)) represent an important
class of compounds with interesting structures and fascinating
properties.1-39 They feature planar or distorted nine-
* To whom correspondence should be addressed. E-mail: dias@uta.edu.
Phone: 817-272-3813.
(1) La Monica, G.; Ardizzoia, G. A. Prog. Inorg. Chem. 1997, 46, 151-
(9) Murray, H. H.; Raptis, R. G.; Fackler, J. P., Jr. Inorg. Chem. 1988,
27, 26-33.
238.
(2) Banditelli, G.; Bandini, A. L.; Bonati, F.; Goel, R. G.; Minghetti, G.
Gazz. Chim. Ital. 1982, 112, 539-42.
(3) Raptis, R. G.; Fackler, J. P., Jr. Inorg. Chem. 1988, 27, 4179-82.
(4) Bonati, F.; Burini, A.; Pietroni, B. R.; Galassi, R. Gazz. Chim. Ital.
1993, 123, 691-5.
(5) Bonati, F.; Minghetti, G.; Banditelli, G. Chem. Comm. 1974, 88-9.
(6) Barbera, J.; Elduque, A.; Gimenez, R.; Oro, L. A.; Serrano, J. L.
Angew. Chem., Int. Ed. Engl. 1997, 35, 2832-5.
(7) Barbera, J.; Elduque, A.; Gimenez, R.; Lahoz, F. J.; Lopez, J. A.;
Oro, L. A.; Serrano, J. L. Inorg. Chem. 1998, 37, 2960-7.
(8) Bovio, B.; Bonati, F.; Banditelli, G. Inorg. Chim. Acta 1984, 87, 25-
33.
(10) Singh, K.; Long, J. R.; Stavropoulos, P. J. Am. Chem. Soc. 1997, 119,
2942-3.
(11) Ardizzoia, G. A.; La Monica, G.; Maspero, A.; Moret, M.; Masciocchi,
N. Inorg. Chem. 1997, 36, 2321-8.
(12) Ardizzoia, G. A.; Monica, G. L. Inorg. Synth. 1997, 31, 299-302.
(13) Kim, S. J.; Kang, S. H.; Park, K.-M.; Kim, H.; Zin, W.-C.; Choi,
M.-G.; Kim, K. Chem. Mater. 1998, 10, 1889-93.
(14) Ardizzoia, G. A.; La Monica, G.; Maspero, A.; Masciocchi, N.; Moret,
M. Eur. J. Inorg. Chem. 1999, 1301-7.
(15) Ehlert, M. K.; Rettig, S. J.; Storr, A.; Thompson, R. C.; Trotter, J.
Can. J. Chem. 1990, 68, 1444-9.
(16) Raptis, R. G.; Fackler, J. P., Jr. Inorg. Chem. 1990, 29, 5003-6.
10.1021/ic062374k CCC: $37.00
Published on Web 03/22/2007
© 2007 American Chemical Society
Inorganic Chemistry, Vol. 46, No. 8, 2007 2979

Dias et al.
systems,10,40 acid/base and host/guest chemistry,34 and as
luminescent materials.23,27,32,34,41
An area of research activity in our laboratory concerns
the chemistry of Cu(I), Ag(I), and Au(I) complexes of
fluorinated pyrazolate ligands.19,27,30,34,38-40,42 Although fluoro
substituents usually provide favorable properties such as
volatility and thermal and oxidative stability, and coinage
metal pyrazolates have been investigated for many years,43
the coinage metal complexes of fluorinated pyrazolates have
gained relatively less attention. Our first contribution to this
area concerns the synthesis of {[3,5-(CF3)2Pz]Cu}3 and
{[3,5-(CF3)2Pz]Ag}3 ([3,5-(CF3)2Pz]- ) 3,5-bis(trifluoro-
methyl)pyrazolate, Figure 1).19 These metal adducts and the
related gold analog display fascinating luminescence proper-
ties. For example, {[3,5-(CF3)2Pz]Cu}3 shows bright lumi-
nescence upon exposure to UV radiation. The emission colors
of solids and frozen solutions of the trimeric compounds,
such as {[3,5-(CF3)2Pz]Cu}3, show interesting trends with
Figure 1. Coinage metal complexes of 3,5-bis(trifluoromethyl)pyrazolates.
dramatic sensitivities to temperature, solvent, concentration,
and excitation wavelengths.27,34 These trinuclear coinage
metal pyrazolates also exhibit interesting π-acid/base proper-
ties, and the acidity and basicity can be controlled by the
substituents on the pyrazole ring, as well as by the metal
atom.34 For example, {[3,5-(CH3)2Pz]Au}3 is a π-base,
whereas the fluorinated analog {[3,5-(CF3)2Pz]Au}3 is a
π-acid. Toluene and {[3,5-(CF3)2Pz]Au}3 form extended
columnar structures through face-to-face contacts between
the dimer-of-trimer units of the gold pyrazolate and toluene.34
In this paper, we describe the synthesis of a series of silver-
(I) adducts containing fluorinated pyrazolate ligands and
some of their solid-state structures. In particular, we have
examined the effect of pyrazolyl ring substituents on the
structure because, with Cu(I) and Au(I), bulky groups on
pyrazolates lead to tetramers and even hexamers rather than
the common trimers.9,31,44-46 While this work is in progress,
the synthesis of {[3-(CF3),5-(But)Pz]Ag}3 and its use as a
CVD precursor for the deposition of silver appeared in the
literature.22 The only other report on a fluorinated silver
pyrazolate concerns our work on structural, photophysical,
and computational studies on {[3,5-(CF3)2Pz]Ag}3 and its
reactivity with nitrogen-containing heterocycles.19,34,40,42
(17) Meyer, F.; Jacobi, A.; Zsolnai, L. Chem. Ber./Recl. 1997, 130, 1441-
7.
(18) Ford, P. C.; Cariati, E.; Bourassa, J. Chem. ReV. 1999, 99, 3625-47.
(19) Dias, H. V. R.; Polach, S. A.; Wang, Z. J. Fluorine Chem. 2000, 103,
163-9.
(20) Masciocchi, N.; Cairati, P.; Sironi, A. Powder Diffr. 1998, 13, 35-
40.
(21) Masciocchi, N.; Moret, M.; Cairati, P.; Sironi, A.; Ardizzoia, G. A.;
La Monica, G. J. Am. Chem. Soc. 1994, 116, 7668-76.
(22) Chi, Y.; Lay, E.; Chou, T.-Y.; Song, Y.-H.; Carty, A. J. Chem. Vap.
Deposition 2005, 11, 206-12.
(23) Enomoto, M.; Kishimura, A.; Aida, T. J. Am. Chem. Soc. 2001, 123,
5608-9.
(24) Burini, A.; Bravi, R.; Fackler, J. P., Jr.; Galassi, R.; Grant, T. A.;
Omary, M. A.; Pietroni, B. R.; Staples, R. J. Inorg. Chem. 2000, 39,
3158-65.
(25) Mohamed, A. A.; Perez, L. M.; Fackler, J. P. Inorg. Chim. Acta 2005,
358, 1657-62.
(26) Burini, A.; Mohamed, A. A.; Fackler, J. P. Comments Inorg. Chem.
2003, 24, 253-80.
(27) Dias, H. V. R.; Diyabalanage, H. V. K.; Rawashdeh-Omary, M. A.;
Franzman, M. A.; Omary, M. A. J. Am. Chem. Soc. 2003, 125, 12072-
3.
(28) Maspero, A.; Brenna, S.; Galli, S.; Penoni, A. J. Organomet. Chem.
2003, 672, 123-9.
Experimental Section
(29) Yang, G.; Raptis, R. G. Inorg. Chem. 2003, 42, 261-3.
(30) Omary, M. A.; Rawashdeh-Omary, M. A.; Diyabalanage, H. V. K.;
Dias, H. V. R. Inorg. Chem. 2003, 42, 8612-4.
(31) Fujisawa, K.; Ishikawa, Y.; Miyashita, Y.; Okamoto, K.-I. Chem. Lett.
2004, 33, 66-7.
General Procedures. All manipulations were carried out under
an atmosphere of purified nitrogen using standard Schlenk tech-
niques. Solvents were purchased from commercial sources, distilled
from conventional drying agents, and degassed by the freeze-
pump-thaw method twice prior to use. The glassware was oven
dried at 150 °C overnight. NMR spectra were recorded at 25 °C
on a JEOL Eclipse 500 spectrometer (1H, 500.16 MHz; 19F, 470.62
MHz). Proton chemical shifts are reported in parts per million versus
Me4Si. 19F NMR chemical shifts were referenced relative to external
CFCl3. Infrared spectra were recorded on a JASCO FT-IR 410
spectrometer. Melting points were obtained on a Mel-Temp II
apparatus and were not corrected. Elemental analyses were per-
formed using a Perkin-Elmer Model 2400 CHN analyzer. [3-(CF3)-
Pz]H,47 [3-(CF3),5-(CH3)Pz]H,48 [3-(CF3),5-(Ph)Pz]H,49 [3-(C3F7),5-
(32) Dodge, M. W.; Wacholtz, W. F.; Mague, J. T. J. Chem. Crystallogr.
2005, 35, 5-12.
(33) Kishimura, A.; Yamashita, T.; Aida, T. J. Am. Chem. Soc. 2005, 127,
179-83.
(34) Omary, M. A.; Rawashdeh-Omary, M. A.; Gonser, M. W. A.;
Elbjeirami, O.; Grimes, T.; Cundari, T. R.; Diyabalanage, H. V. K.;
Gamage, C. S. P.; Dias, H. V. R. Inorg. Chem. 2005, 44, 8200-10.
(35) Torralba, M. C.; Ovejero, P.; Mayoral, M. J.; Cano, M.; Campo, J.
A.; Heras, J. V.; Pinilla, E.; Torres, M. R. HelV. Chim. Acta 2004, 87,
250-63.
(36) Yamada, S.; Ishida, T.; Nogami, T. Dalton Trans. 2004, 898-903.
(37) Mohamed, A. A.; Burini, A.; Fackler, J. P., Jr. J. Am. Chem. Soc.
2005, 127, 5012-3.
(38) Dias, H. V. R.; Diyabalanage, H. V. K.; Eldabaja, M. G.; Elbjeirami,
O.; Rawashdeh-Omary, M. A.; Omary, M. A. J. Am. Chem. Soc. 2005,
127, 7489-501.
(44) Ardizzoia, G. A.; Cenini, S.; La Monica, G.; Masciocchi, N.; Moret,
M. Inorg. Chem. 1994, 33, 1458-63.
(39) Dias, H. V. R.; Diyabalanage, H. V. K. Polyhedron 2006, 25, 1655-
61.
(45) Yang, G.; Raptis, R. G. Inorg. Chim. Acta 2003, 352, 98-104.
(46) Raptis, R. G.; Murray, H. H., III; Fackler, J. P., Jr. Chem. Commun.
1987, 737-9.
(40) Grimes, T.; Omary, M. A.; Dias, H. V. R.; Cundari, T. R. J. Phys
Chem. A 2006, 110, 5823-30.
(41) Omary, M. A.; Mohamed, A. A.; Rawashdeh-Omary, M. A.; Fackler,
J. P. Coord. Chem. ReV. 2005, 249, 1372-81.
(42) Dias, H. V. R.; Diyabalanage, H. V. K.; Gamage, C. S. P. Chem.
Commun. 2005, 1619-21.
(47) Gerus, I. I.; Gorbunova, M. G.; Vdovenko, S. I.; Yagupol’skii, Y. L.;
Kukhar, V. P. Zh. Org. Khim. 1990, 26, 1877-83.
(48) Atwood, J. L.; Dixon, K. R.; Eadie, D. T.; Stobart, S. R.; Zaworotko,
M. J. Inorg. Chem. 1983, 22, 774-9.
(43) Buchner, E. Berichte 1889, 22, 842.
(49) Dias, H. V. R.; Goh, T. K. H. H. Polyhedron 2004, 23, 273-282.
2980 Inorganic Chemistry, Vol. 46, No. 8, 2007

Ag(I) Complexes of Fluorinated Pyrazolates
Table 1. 1H NMR and 19F NMR Spectroscopic Data in CDCl3 at Room Temperature
pyrazole
1H
19F
silver pyrazolate
1H
19F
[3-(CF3)Pz]H
6.63 (s, 1H)
7.67 (s, 1H)
12.34 (br s, 1H)
1.34 (s, 3H)
6.31 (s, 1H)
11.82 (br s, 1H)
6.77 (s, 1H)
7.42 (m, 1H)
7.47 (m, 2H)
7.57 (m, 2H)
10.67 (br s, 1H)
1.34 (s, 9H)
6.31 (s, 1H)
10.29 (br s, 1H)
1.34 (s, 9H)
-61.7 (s)
-61.9 (s)
-62.2 (s)
{[3-(CF3)Pz]Ag}3
6.68 (br s, 3H)
7.53 (br s, 3H)
-60.2 (s)
-59.4 (s)
-60.2 (s)
[3-(CF3),5-(CH3)Pz]H
[3-(CF3),5-(Ph)Pz]H
{[3-(CF3),5-(CH3)Pz]Ag}3
{[3-(CF3),5-(Ph)Pz]Ag}3
2.26 (s, 9H)
6.39 (s, 3H)
6.82 (s, 3H)
7.50 (m, 9H)
7.68 (m, 6H)
[3-(CF3),5-(But)Pz]H
[3-(C3F7),5-(But)Pz]H
-62.2 (s)
{[3-(CF3),5-(But)Pz]Ag}3
{[3-(C3F7),5-(But)Pz]Ag}3
1.49 (s, 27H)
6.56 (s, 3H)
-59.5 (s)
-80.2 (t, 3F, J ) 9.79 Hz)
-110.6 (q, 2F, J ) 9.79 Hz)
-126.9 (s, 2F)
1.35 (s, 27H)
6.42 (s, 3H)
-79.9 (t, 9F, J ) 9.79 Hz)
-108.4 (br s, 6F)
-126.0 (s, 6F)
6.34 (s, 1H)
10.31(br s, 1H)
19
(But)Pz]H,50 [3-(CF3),5-(But)Pz]H,50 and {[3,5-(CF3)2Pz]Ag}3
was removed under reduced pressure to obtain {[3-(CF3),5-(But)-
Pz]Ag}3 as a yellowish white solid. X-ray quality crystals were
grown from dichloromethane/hexane at 5 °C. Yield: 88%. mp:
124-126 °C. IR (KBr, cm-1): νj 3174, 3111, 3055, 2970, 2871,
2362, 1574, 1502, 1483, 1464, 1425, 1392, 1369, 1302, 1257, 1221,
1165, 1136, 1088, 1041, 1011, 982, 806, 746. Anal. Calcd for
C24H30F9N3Ag3: C, 32.13; H, 3.37; N, 9.37. Found: C, 33.43; H,
3.40; N, 9.37.
{[3-(C3F7),5-(But)Pz]Ag}3. A mixture of Ag2O (0.21 g, 0.91
mmol) and [3-(C3F7),5-(But)Pz]H (0.38 g, 1.65 mmol) in toluene
(15.0 mL) was protected from light using aluminum foil and
refluxed overnight. After it was cooled, the solution was filtered
through a bed of Celite, and the filtrate was collected. The solvent
was removed under reduced pressure to obtain {[3-(C3F7),5-(But)-
Pz]Ag}3 as a colorless solid. X-ray quality crystals were grown
from hexane at 5 °C. Yield: 92%. mp: 183-185 °C. IR (KBr,
cm-1): νj 3186, 3105, 2972, 1653, 1570, 1454, 1417, 1371, 1348,
1298, 1223, 1184, 1119, 1011, 995, 877, 748. Anal. Calcd for
C30H30Ag3N6F21: C, 30.10; H, 2.53; N, 7.02. Found: C, 30.86; H,
2.76; N, 6.78. X-ray quality crystals were grown from toluene at 5
°C, resulting in the formation of a sandwich complex {[Ag3]′‚
were prepared by literature methods. The H and 19F NMR data
1
are summarized in Table 1.
{[3-(CF3)Pz]Ag}3. Ag2O (0.31 g, 1.34 mmol) and [3-(CF3)Pz]H
(0.37 g, 2.67 mmol) were mixed in toluene (15.0 mL). The resulting
mixture was protected from light using aluminum foil and was
refluxed overnight. After it was cooled, the solution was filtered
through a bed of Celite to remove insoluble material. The filtrate
was collected, and the solvent was removed under reduced pressure
to yield {[3-(CF3)Pz]Ag}3 as a white solid. Yield: 88%. mp: 192-
195 °C. IR (KBr, cm-1): νj 1724, 1520, 1346, 1245, 1171, 1115,
991, 783. Anal. Calcd for C12H6Ag3N6F9: C, 19.78; H, 0.83; N,
11.53. Found: C, 20.28; H, 0.90; N, 11.55.
{[3-(CF3),5-(CH3)Pz]Ag}3. Ag2O (0.42 g, 1.82 mmol) and
[3-(CF3),5-(CH3)Pz]H (0.50 g, 3.30 mmol) were mixed in toluene
(20.0 mL). The resulting mixture was protected from light using
aluminum foil and was refluxed overnight. After it was cooled,
the solution was filtered through a bed of Celite. The filtrate was
collected, and the solvent was removed under reduced pressure to
produce {[3-(CF3),5-(CH3)Pz]Ag}3 as a colorless solid. X-ray
quality crystals were grown from hexane at 5 °C. Yield: 95%.
mp: 270-273 °C (dec). IR (KBr, cm-1): νj 3143, 2927, 2362, 1535,
1485, 1458, 1342, 1242, 1173, 1138, 1001, 791. Anal. Calcd for
C15H12Ag3N6F9: C, 23.37; H, 1.57; N, 10.9. Found: C, 23.48; H,
1.45; N, 10.92.
{[3-(CF3),5-(Ph)Pz]Ag}3. Ag2O (0.14 g, 0.60 mmol) and
[3-(CF3),5-(Ph)Pz]H (0.35 g, 1.19 mmol) were mixed in toluene
(20.0 mL). The resulting mixture was protected from light using
aluminum foil and was refluxed overnight. After it was cooled,
the solution was filtered through a bed of Celite to remove insoluble
black material. The filtrate was collected, and the solvent was
removed under reduced pressure to give {[3-(CF3),5-(Ph)Pz]Ag}3
as an off-white solid. The product was recrystallized using toluene/
CH2Cl2. Yield: 97%. mp: 199-201 °C (dec). IR (KBr, cm-1): νj
3045, 2962, 1604, 1541, 1510, 1461, 1427, 1281, 1250, 1157, 1117,
1011, 910, 804, 762, 690. Anal. Calcd for C30H18Ag3N6F9: C,
37.65; H, 1.90; N, 8.78. Found: C, 37.91; H, 1.45; N, 9.17.
{[3-(CF3),5-(But)Pz]Ag}3. Ag2O (0.21 g, 0.91 mmol) and
[3-(CF3),5-(But)Pz]H (0.32 g, 1.65 mmol) were mixed in toluene
(15.0 mL). The resulting mixture was protected from light using
aluminum foil and refluxed overnight. After it was cooled, the
solution was filtered through a bed of Celite to remove some
insoluble black material. The filtrate was collected, and the solvent
[toluene]}∞ ({[3-(C3F7),5-(But)Pz]Ag}3
)
[Ag3]′). mp:
174-176 °C. 1H NMR (CDCl3): δ 1.35 (s, 27H, But), 2.33 (s, 3H,
tol-CH3), 6.42 (s, 3H, Pz-H), 7.17 (m, 5H, tol-H). 19F NMR
(CDCl3): δ -79.9 (t, 3F, CF3, JFF ) 9.79 Hz), -108.4 (br s, 2F,
CF2), -126.0 (s, 2F, CF2). Anal. Calcd for C37H38N6F21Ag3: C,
34.47; H, 2.97; N, 6.52. Found: C, 34.91; H, 2.66; N, 6.15.
{[Ag3]2‚[toluene]}∞ ({[3,5-(CF3)2Pz]Ag}3 ) [Ag3]). {[3,5-
(CF3)2Pz]Ag}3 (0.50 g, 0.536 mmol) was dissolved in 2.5 mL of
toluene and kept at 5 °C to obtain X-ray quality crystals of {[Ag3]2‚
1
[toluene]}∞. mp: 220 °C. H NMR (CDCl3): δ 2.31 (s, tol-CH3),
7.03 (s, Pz-H), 7.17 (m, tol-H). 19F NMR (CDCl3): δ -60.9 (s,
CF3). Anal. Calcd for C37H14N12F36Ag6: C, 22.70; H, 0.72; N, 8.59.
Found: C, 23.23; H, 0.69; N, 8.12.
X-ray Crystallographic Data. A suitable crystal of the silver
complex covered with a layer of hydrocarbon oil was selected,
mounted with paratone-N oil in a cryoloop, and immediately placed
in the low-temperature nitrogen stream for the low-temperature
work or mounted on a glass fiber using five minute epoxy glue for
room temperature data collections. The X-ray intensity data of
{[3-(CF3),5-(CH3)Pz]Ag}3, {[Ag3]2‚[toluene]}∞, and {[Ag3]′‚
[toluene]}∞ were measured at 100(2) K on a Bruker SMART APEX
CCD area detector system equipped with a Oxford Cryosystems
700 Series cooler, a graphite monochromator, and a Mo KR fine-
focus sealed tube (λ ) 0.710 73 Å). The detector was placed at a
(50) Zelenin, K. N.; Tugusheva, A. R.; Yakimovich, S. I.; Alekseev, V.
V.; Zerova, E. V. Chem. Heterocycl. Compd. 2002, 38, 668-76.
Inorganic Chemistry, Vol. 46, No. 8, 2007 2981

Dias et al.
Table 2. X-ray Crystallographic Data for {[3-(CF3),5-(CH3)Pz]Ag}3, {[3-(CF3),5-(But)Pz]Ag}3, {[3-(C3F7),5-(But)Pz]Ag}3, {[Ag3]2‚[toluene]}∞, and
{[Ag3]′‚[toluene]}∞ ([Ag3] ) {[3,5-(CF3)2Pz]Ag}3, [Ag3]′ ) {[3-(C3F7),5-(But)Pz]Ag}3)
{[3-(CF3),5-(CH3)Pz]Ag}3 {[3-(CF3),5-(But)Pz]Ag}3 {[3-(C3F7),5-(But)Pz]Ag}3 {[Ag3]′‚[toluene]}∞ {[Ag3]2‚[toluene]}∞
empirical formula
fw
temp
wavelength
cryst syst
space group
unit cell dimensions
C15H12Ag3F9N6
770.89
100(2) K
0.71073 Å
triclinic
C24H30Ag3F9N6
897.15
293(2) K
0.71073 Å
monoclinic
P21/n
C
30 H30Ag3F21N6
C37H38Ag3F21N6
1289.34
100(2) K
0.71073 Å
monoclinic
P21/c
C18.50H7Ag3F18N6
1197.21
293(2) K
0.71073 Å
monoclinic
P21/c
978.91
100(2) K
0.71073 Å
triclinic
P1h
P1h
a
b
c
8.4759(9) Å
11.0492(12) Å
12.1947(13) Å
68.974°
14.452(2) Å
10.0648(17) Å
21.350(4) Å
90°
12.2012(14) Å
30.843(4) Å
11.477(2) Å
90°
15.4624(8) Å
25.0706(13) Å
12.3999(6) Å
90°
13.1022(5) Å
22.6659(8) Å
23.6928(9) Å
77.841(1)°
R
â
77.129(1)°
93.223(11)°
90°
103.525(12)°
90°
107.197(1)°
90°
75.896(1)°
γ
83.360(1)°
89.568(1)°
vol
1038.43(19) Å3
2
3100.6(9) Å3
4
4199.4(10) Å3
4
4591.9(4) Å3
4
6666.8(4) Å3
10
Z
density (calcd)
R1, wR2 [I > 2σ(I)]
R1, wR2 (all data)
2.466 Mg/m3
0.0231, 0.0587
0.0250, 0.0600
1.922 Mg/m3
0.0275, 0.0634
0.0358, 0.0668
1.894 Mg/m3
0.0590, 0.1541
0.0829, 0.1653
1.865 Mg/m3
0.0214, 0.0517
0.0248, 0.0537
2.439 Mg/m3
0.0298, 0.0727
0.0340, 0.0752
distance of 5.995 cm from the crystal. The data frames were
integrated with the Bruker SAINT-Plus software package. Data were
corrected for absorption effects using the multiscan technique
(SADABS). The X-ray intensity data of {[3-(CF3),5-(But)Pz]Ag}3
and {[3-(C3F7),5-(But)Pz]Ag}3 were measured at room temperature
on a Siemens P4 diffractometer equipped with graphite-monochro-
mated Mo KR radiation (λ ) 0.710 73 Å). The absorption
corrections for these two crystals were based on ψ scan data. The
structures were solved and refined using Bruker SHELXTL (version
6.14). A summary of the X-ray data are presented in Table 2.
Further details of the data collection and refinement are given in
the Supporting Information (CIF file).
{[Ag3]′‚[toluene]}∞ ([Ag3]′ ) {[3-(C3F7),5-(But)Pz]Ag}3) crystal-
lizes in the P21/c space group. All the non-hydrogen atoms were
refined anisotropically. The hydrogen atoms were placed at
calculated positions and refined using a riding model. The final
full-matrix least-squares refinement on F2 with 614 variables
converged at R1 ) 2.14% for observed data and wR2 ) 5.37%
for all data. The goodness-of-fit was 1.044.
{[Ag3]2‚[toluene]}∞ ({[Ag3]2 ) {[3,5-(CF3)2Pz]Ag}3) crystallizes
in the P1h space group. There are ten {[3,5-(CF3)2Pz]Ag}3 units
and five toluene molecules in the unit cell, and one of the toluene
molecules is disordered across a center of symmetry. The bowl-
shaped {[3,5-(CF3)2Pz]Ag}3 units form dimers of trimers. Several
CF3 groups show rotational disorder, which was modeled success-
fully. The carbon atoms of the disordered toluene molecule were
refined isotropically. All other non-hydrogen atoms were refined
anisotropically. The hydrogen atoms were placed at calculated
positions and refined using a riding model. The final full-matrix
least-squares refinement on F2 with 2130 variables converged at
R1 ) 2.98% for observed data and wR2 ) 7.52% for all data. The
goodness-of-fit was 1.020
{[3-(CF3),5-(CH3)Pz]Ag}3 crystallizes in the P1h space group as
a dimer of trimers. The dimer of trimers sits on an inversion center.
In each pyrazolyl group, the 3- and 5-positions show either a CF3/
CH3 or CH3/CF3 occupancy pattern (i.e., each site is partially
occupied by CF3 or CH3), indicating positional disorder. This
disorder was resolved satisfactorily, and the site occupancies
were refined. All the non-hydrogen atoms were refined anisotro-
pically. The hydrogen atoms were placed at calculated positions
and refined using a riding model. The final full-matrix least-squares
refinement on F2 with 388 variables converged at R1 ) 2.31% for
observed data and wR2 ) 6.00% for all data. The goodness-of-fit
was 1.042.
{[3-(CF3),5-(But)Pz]Ag}3 crystallizes in the P21/n space group.
{[3-(CF3),5-(But)Pz]Ag}3 adopts a bowl shape. Two of the three
CF3 groups show rotational disorder. It was modeled successfully.
All the non-hydrogen atoms were refined anisotropically. The
hydrogen atoms were placed at calculated positions and
refined using a riding model. The final full-matrix least-squares
refinement on F2 with 444 variables converged at R1 ) 2.75% for
observed data and wR2 ) 6.88% for all data. The goodness-of-fit
was 1.093.
{[3-(C3F7),5-(But)Pz]Ag}3 crystallizes in the P21/c space group.
The Ag3N6 core is significantly twisted. The fluorine atoms of one
of the C3F7 groups are disordered, and the disorder in the CF3
moiety was modeled. All non-hydrogen atoms, except for the atoms
of the CF2CF3 portion in the disordered C3F7 group, were refined
anisotropically. The hydrogen atoms were placed at calculated
positions and refined using a riding model. The final full-matrix
least-squares refinement on F2 with 519 variables converged at R1
) 5.90% for observed data and wR2 ) 16.53% for all data. The
goodness-of-fit was 1.038.
Results and Discussion
The silver pyrazolates {[3-(CF3)Pz]Ag}3, {[3-(CF3),5-
(CH3)Pz]Ag}3, {[3-(CF3),5-(Ph)Pz]Ag}3, {[3-(CF3),5-(But)-
Pz]Ag}3, and {[3-(C3F7),5-(But)Pz]Ag}3 were prepared by
treatment of the corresponding pyrazole with a slight molar
excess of silver(I) oxide in toluene (Figure 2).19,22,39 They
were obtained in high yields (>80%). This route provides a
convenient and economical method for the synthesis of silver
pyrazolates. It also appears to be fairly general because it is
possible to use a wide spectrum of pyrazoles such as the
electron-rich [3,5-(i-Pr)2Pz]H, weakly coordinating [3,5-
(CF3)2Pz]H, and sterically demanding [3-(C3F7),5-(But)Pz]H
successfully in this reaction.19,22,39
Silver pyrazolates {[3-(CF3)Pz]Ag}3, {[3-(CF3),5-(CH3)-
Pz]Ag}3, {[3-(CF3),5-(Ph)Pz]Ag}3, {[3-(CF3),5-(But)Pz]-
Ag}3, and {[3-(C3F7),5-(But)Pz]Ag}3 are air stable crystalline
solids. They are readily soluble in most of the common
organic solvents such as hexane, benzene, dichloromethane,
acetonitrile, toluene, and tetrahydrofuran. {[3-(CF3),5-(CH3)-
Pz]Ag}3 has the highest melting point (270-273 °C) among
the silver pyrazolates illustrated in Figure 2. Others melt near
2982 Inorganic Chemistry, Vol. 46, No. 8, 2007

Ag(I) Complexes of Fluorinated Pyrazolates
Figure 2. Synthetic route to silver pyrazolates using Ag2O as the silver source.
Figure 3. Molecular structure of {[3-(CF3),5-(CH3)Pz]Ag}3 (hydrogen
atoms have been omitted for clarity) and the extended chains of {[3-(CF3),5-
(CH3)Pz]Ag}3 formed via Ag‚‚‚Ag contacts (all except nitrogen and silver
atoms have been omitted for clarity).
Figure 5. Molecular structure of {[3-(C3F7),5-(But)Pz]Ag}3 (hydrogen
atoms have been omitted for clarity) and a side view showing the
twisted Ag3N6 core (pyrazolyl ring substituents have been omitted for
clarity).
[toluene]}∞ (formed during the isolation of {[3-(C3F7),5-
(But)Pz]Ag}3 and {[3,5-(CF3)2Pz]Ag}3 from toluene) were
characterized using X-ray crystallography. Despite several
attempts, we could not obtain crystals of {[3-(CF3)Pz]Ag}3
and {[3-(CF3),5-(Ph)Pz]Ag}3 suitable for X-ray diffraction
studies.
Figure 4. Molecular structure of {[3-(CF3),5-(But)Pz]Ag}3 (hydrogen
atoms have been omitted for clarity) and a view showing relative
arrangement of the dimers of trimers and the closest Ag‚‚‚Ag contacts (all
except nitrogen and silver atoms have been omitted for clarity).
X-ray data of {[3-(CF3),5-(CH3)Pz]Ag}3 show that it
adopts a trinuclear structure (Figure 3) with an essentially
planar nine-membered Ag3N6 metallacycle. Neighboring
pairs of these trinuclear units are linked by two equal and
relatively short Ag‚‚‚Ag contacts (3.3553(4) Å) across a
crystallographic inversion center. The dimer of trimers
interacts further with their neighbors via additional Ag‚‚‚
Ag links (3.4263(4) Å), forming extended stepladder-shaped
columns (Figure 3). These Ag‚‚‚Ag distances are less than
the sum of the van der Waals radii of two silver atoms (3.44
Å)51 but longer than the Ag-Ag distance in the open-shell
metallic silver (2.889 Å).10,51
or below 200 °C. All these silver pyrazolates were character-
1
ized using H and 19F NMR spectroscopy (Table 1), FT-IR
spectroscopy, and CHN analysis. As expected, the proton
NMR spectra of the silver pyrazolates lack the broad peak
corresponding to the N-H proton of the free pyrazoles. The
19F NMR spectra of {[3-(CF3)Pz]Ag}3, {[3-(CF3),5-(CH3)-
Pz]Ag}3, {[3-(CF3),5-(Ph)Pz]Ag}3, and {[3-(CF3),5-(But)-
Pz]Ag}3 show only one signal each with a chemical shift
slightly downfield from that of the respective free pyrazole.
The 1H NMR signal corresponding to the protons at pyrazolyl
ring 4-position also shows a small downfield shift.
{[3-(CF3),5-(But)Pz]Ag}3 also features a trinuclear struc-
ture (Figure 4) but has a slightly concave shape. These
Compounds {[3-(CF3),5-(CH3)Pz]Ag}3, {[3-(CF3),5-(But)-
Pz]Ag}3, and {[3-(C3F7),5-(But)Pz]Ag}3, as well as the
π-acid/base adducts {[Ag3]2‚[toluene]}∞ and {[Ag3]′‚
(51) (a) For the most widely used, but probably some what underestimated,
van der Waals radii, see: Bondi, A. J. Phys. Chem. 1964, 68, 441-
51. (b) For other suggested values, see: Batsanov, S. S. Inorg. Mater.
2001, 37, 871-85 and references therein.
Inorganic Chemistry, Vol. 46, No. 8, 2007 2983

Dias et al.
(But)Pz]Ag}3 units. There are also close intertrimer Ag‚‚‚F
(3.096 Å) contacts.52,53 These distances are within the sum
of the van der Waals radii of Ag and F (3.19 Å).54 There are
also somewhat close (2.89 Å; cf. van der Waals contact of
Ag and H, 2.92 Å) intertrimer Ag‚‚‚H contacts between silver
atoms and one of the hydrogens of the t-butyl group.
However, these Ag‚‚‚H and Ag‚‚‚F contacts may not be that
significant considering that they are not notably shorter than
the van der Waals contact distance and are probably a result
of crystal packing.
Overall, X-ray crystallographic data of molecules like
{[3-(CF3),5-(But)Pz]Ag}3 and {[3-(C3F7),5-(But)Pz]Ag}3 show
that silver pyrazolates can accommodate large substituents
on the pyrazolyl ring 3- and 5-positions while maintaining
the trinuclear structures with Ag3N6 cores. Tetramers like
{[3,5-(But)2Pz]Ag}4, reported recently by Raptis et al., are
very rare among silver pyrazolates.55 This is probably a direct
result of the size of the coinage metal ion. Silver is the largest
member of the coinage metal family. For comparison, the
covalent radii of two-coordinate Cu(I), Ag(I), and Au(I) are
1.11, 1.33, and 1.25 Å, respectively.34,56 With copper and
gold pyrazolates, bulky substituents at the 3- and 5-position
of the pyrazolyl moiety often lead to different aggregates
such as tetramers and even hexamers.9,31,44-46
Figure 6. Sandwich structures of {[Ag3]2‚[toluene]}∞ (left) and {[Ag3]′‚
[toluene]}∞ (right): [Ag3] ) {[3,5-(CF3)2Pz]Ag}3 and [Ag3]′ ) {[3-(C3F7),5-
(But)Pz]Ag}3. Toluene molecules are depicted in yellow. Pyrazolyl ring
substituents and hydrogen atoms have been omitted for clarity.
trimers crystallize in pairs, essentially forming dimers of
trimers. The six silver atom core of the two trimer units
adopts a chair conformation. Even the closest intertrimer
Ag‚‚‚Ag separation (3.4804(7) Å) in {[3-(CF3),5-(But)Pz]-
Ag}3 (see Figure 4) is not as short as the intertrimer Ag‚‚‚
Ag contacts of {[3-(CF3),5-(CH3)Pz]Ag}3. This may be a
result of the steric repulsions between the pyrazolyl ring
substituents on the adjacent trimers, which prevent the
formation of shorter Ag‚‚‚Ag links. The concave shape of
{[3-(CF3),5-(But)Pz]Ag}3 also appears to be primarily a result
of the intertrimer steric interactions between the pyrazolyl
ring substituents. These repulsions push the pyrazolyl rings
away from the mid plane of the dimer of trimers leading to
the bowl-shaped conformation. These steric interactions also
cause the N-Ag-N angle to deviate significantly from the
ideal 180°. For example, the N-Ag-N bond angles of this
adduct range from 166.94(16) to 172.99(15)°. In {[3-(CF3),5-
(But)Pz]Ag}3, the neighboring dimer-of-trimer units reside
too far apart (e.g., closest Ag‚‚‚Ag separation ) 6.270 Å)
to form extended chain structures via Ag‚‚‚Ag contacts.
Interestingly, despite the presence of two large substituents
on the pyrazolyl ring, [3-(C3F7),5-(But)Pz]Ag also trimerizes
and forms the typical trinuclear unit (Figure 5). These
trinuclear units pack in a staggered fashion (i.e., with a lateral
slippage), forming zigzag chains that do not feature any
intertrimer Ag‚‚‚Ag contacts (the closest separation is at
5.376 Å). The nine-membered Ag3N6 metallacycle in {[3-
(C3F7),5-(But)Pz]Ag}3 shows a significant deviation from
planarity. Although it is tempting to attribute this solely to
the intratrimer steric effects of having C3F7 and t-butyl
substituents on the adjacent pyrazolyl ligands, the relatively
planar Ag3N6 rings in the {[3-(C3F7),5-(But)Pz]Ag}3‚toluene
adduct (see below) points to an alternative possibility. It
appears that this ring twisting is caused primarily by the
intertrimer steric interactions. The C3F7 groups of the {[3-
(C3F7),5-(But)Pz]Ag}3 adduct point above and below the
Ag3N6 plane to avoid t-butyl substituents on the adjacent
pyrazolyl rings. However, this arrangement of the substitu-
ents leads to adverse steric interactions with the neighboring
trimers causing large ring distortions in the {[3-(C3F7),5-
Selected bond distances and angles of trimeric silver(I)
pyrazolates are listed in Table 3. Data show that the Ag-N
bond distances of {[(3-(CF3),5-(CH3)Pz]Ag}3, {[3-(CF3),5-
(But)Pz]Ag}3, and {[3-(C3F7),5-(But)Pz]Ag}3 are very simi-
lar. Even silver pyrazolates bearing much more weakly
coordinating pyrazolates or electron rich pyrazolates have
similar Ag-N bond lengths. For example, the ranges of the
19
Ag-N bond distances of {[3,5-(CF3)2Pz]Ag}3 and {[3,5-
(i-Pr)2Pz]Ag}339 are 2.081(3)-2.096(3) and 2.048(3)-2.088-
(3) Å, respectively. Thus, steric-electronic effects of pyrazolyl
ring substituents have essentially no effect on the Ag-N
bond lengths of these adducts. The N-Ag-N angles,
however, display significant variations. For example, each
silver site in {[3-(CF3),5-(CH3)Pz]Ag}3 shows linear coor-
dination to pyrazolyl nitrogens. The N-Ag-N angles range
from 177.78(10)-178.62(10)°. This molecule contains rela-
tively smaller substituents on the pyrazolyl rings. The
N-Ag-N bond angle range is somewhat wider and the
deviation from ideal 180° is greater in the adducts {[3-
(CF3),5-(But)Pz]Ag}3 and {[3-(C3F7),5-(But)Pz]Ag}3 bearing
bulky pyrazolyl ring substituents. As described earlier, the
distortions in these two latter molecules are primarily a result
of the intertrimer steric repulsions. A twisting of the Ag3N6
core (Figure 5) is an option to alleviate steric repulsions when
the molecules are not constrained by the intertrimer metal-
lophilic contacts. However, when the metal atoms of the
adjacent trimers are close, as in {[3-(CF3),5-(But)Pz]Ag}3
(52) Plenio, H. Chem. ReV. 1997, 97, 3363-84.
(53) Plenio, H. Chem. Bio. Chem. 2004, 5, 650-5.
(54) Winter, M. Webelements Periodic Table, professional edition, 2006,
http://www.webelements.com/.
(55) Guang, Y.; Raptis, R. G. Inorg. Chim. Acta [Online early access]
DOI: 10.1016/j.ica.2006.10.032. Published Online: Nov 9, 2006.
(56) Bayler, A.; Schier, A.; Bowmaker, G. A.; Schmidbaur, H. J. Am. Chem.
Soc. 1996, 118, 7006-7.
2984 Inorganic Chemistry, Vol. 46, No. 8, 2007

Ag(I) Complexes of Fluorinated Pyrazolates
Figure 7. View showing the toluene molecule sandwiched between the two {[3,5-(CF3)2Pz]Ag}3 trimers as in a clam shell.
Table 3. Bond Distances (Å) and Angles (deg) for {[3-(CF3),5-(CH3)Pz]Ag}3, {[3-(CF3),5-(But)Pz]Ag}3, {[3-(C3F7),5-(But)Pz]Ag}3,
{[3,5-(CF3)2Pz]Ag}3, {[3,5-(i-Pr)2Pz]Ag}3, {[Ag3]2‚[toluene]}∞, and {[Ag3]′‚[toluene]}∞ ([Ag3] ) {[3,5-(CF3)2Pz]Ag}3, [Ag3]′ )
{[3-(C3F7),5-(But)Pz]Ag}3)
{[3-(CF3),5-(CH3)Pz]Ag}3
{[3-(CF3),5-(But)Pz]Ag}3
{[3-(C3F7),5-(But)Pz]Ag}3
{[3,5-(CF3)2Pz]Ag}3
Ag-N (range)
2.076(3)-2.084(3)
3.392-3.493
2.086(3)-2.093(4)
3.413-3.489
2.084(8)-2.095(8)
3.394-3.448
5.376
2.081(3)-2.096(3)
3.440-3.541
Ag...Ag (intra, range)
Ag...Ag(inter, shortest)
N-Ag-N (range)
3.3553(4)
3.4804(7)
3.2037(4)
177.78(10)-178.62(10)
166.94(16)-172.99(15)
174.1(4)-179.3(3)
172.01(12)-177.69(13)
{[3,5-(i-Pr)2Pz]Ag}3
{[Ag3]2‚[toluene]}∞
{[Ag3]′‚[toluene]}∞
Ag-N (range)
2.048(3)-2.088(3)
3.324-3.489
2.075(3)-2.108(3)
3.440-3.449
2.098(14)-2.110(14)
3.394-3.409
Ag...Ag (intra, range)
Ag...Ag (inter, shortest)
N-Ag-N (range)
2.9870(4)
3.0911(4)
170.21(13)-177.68(13)
171.42(13)-179.26(14)
175.17(6)-177.27(6)
(or show metallophilic bonding as in dimers of {[3,5-(i-Pr)2,4-
(Br)Pz]Ag}3),39 trimers seem to adopt a bowl shape to relieve
the steric repulsions while preserving the budding (or
existing) Ag‚‚‚Ag linkages.
a considerable Ag‚‚‚Ag distance range.40,58 Toluene in
{[Ag3]2‚[toluene]}∞ serves as the bridge between dimers of
trimers forming extended stacks. Interestingly, the trinuclear
{[3,5-(CF3)2Pz]Ag}3 units curve toward toluene forming a
partially closed “clam shell” shape (Figure 7). In contrast,
the parent {[3,5-(CF3)2Pz]Ag}3 has a significantly more
planar structure.34 The [Ag3] and toluene centroids of {[Ag3]2‚
[toluene]}∞ are separated by a distance that ranges from 3.18
to 3.29 Å. The closest Ag‚‚‚C(toluene) distance is 3.163 Å.
These separations are well within the sum of van der Waals
radii of Ag and C (3.42 Å),54 pointing to the presence of
relatively tight π-acid/base contacts. The closely related gold
complex {[Au3]2‚[toluene]}∞ is known.34 In this adduct, the
[Au3] and toluene centroids are separated by 3.43 and 3.86
Å. The closest Au‚‚‚C(toluene) distance is 3.288 Å. Interest-
ingly, despite the presence of a much smaller metal ion in
{[Au3]2‚[toluene]}∞, the [Au3] and toluene contacts are
significantly longer than the corresponding distances of the
{[Ag3]2‚[toluene]}∞. Thus, these data indicate the presence
of a much stronger contact between [Ag3] and toluene.
The {[3-(C3F7),5-(But)Pz]Ag}3 forms extended stacks of
the type {[Ag3]′‚[toluene]}∞ (Figure 6, {[3-(C3F7),5-(But)-
Pz]Ag}3 ) [Ag3]′), which is the most common stacking
pattern for trinuclear complexes involving d10 metal ions.59-63
Trinuclear complexes of monovalent coinage metal ions
have very interesting π- acid/base properties.41,57 However,
this property is barely explored in the coinage metal
pyrazolate family.34 Computational studies show that com-
pounds of the type {[3,5-(CF3)2Pz]M}3 (M ) Cu, Ag, Au)
are π-acids with the silver(I) analog having the highest
acidity.34 We have been able to isolate two interesting π-acid/
base complexes by exploiting the acidity of {[3,5-(CF3)2Pz]-
Ag}3 and {[3-(C3F7),5-(But)Pz]Ag}3 and the π-basicity of
toluene. The X-ray crystallographic analysis of the crystals
of {[3,5-(CF3)2Pz]Ag}3 obtained from toluene reveals an
interesting supramolecular sandwich structure with the
composition {[Ag3]2‚[toluene]}∞ (Figure 6, {[3,5-(CF3)2Pz]-
Ag}3 ) [Ag3]). {[3,5-(CF3)2Pz]Ag}3 units exist as dimers
of trimers, [Ag3]2. It is possible to identify three types of
[Ag3]2 moieties in these columnar stacks, and they show
different types of face-to-face intertrimer contacts (see
Supporting information for relevant figures). The six silver
atom core of one of these [Ag3]2 units adopts a distorted
trigonal prismatic conformation (with Ag‚‚‚Ag contacts of
3.252, 3.281, and 3.327 Å), while the other two show two
different distorted octahedral arrangements (with closest
Ag‚‚‚Ag separations of 3.091 Å in one, and 3.474 Å in the
other). Such structural variations are not surprising because
Ag‚‚‚Ag contacts between the closed-shell d10 centers are
relatively weak, and the interaction potential is shallow for
(58) Pyykko, P.; Runeberg, N.; Mendizabal, F. Chem.sEur. J. 1997, 3,
1451-7.
(59) Haneline, M. R.; King, J. B.; Gabbai, F. P. Dalton Trans. 2003, 2686-
90.
(60) Tsunoda, M.; Gabbaie, F. P. J. Am. Chem. Soc. 2000, 122, 8335-6.
(61) Burini, A.; Fackler, J. P., Jr.; Galassi, R.; Grant, T. A.; Omary, M.
A.; Rawashdeh-Omary, M. A.; Pietroni, B. R.; Staples, R. J. J. Am.
Chem. Soc. 2000, 122, 11264-5.
(62) Rawashdeh-Omary, M. A.; Omary, M. A.; Fackler, J. P., Jr.; Galassi,
R.; Pietroni, B. R.; Burini, A. J. Am. Chem. Soc. 2001, 123, 9689-
91.
(57) Olmstead, M. M.; Jiang, F.; Attar, S.; Balch, A. L. J. Am. Chem. Soc.
2001, 123, 3260-7.
Inorganic Chemistry, Vol. 46, No. 8, 2007 2985

Dias et al.
amples of argentophilic bonding,10,64-69 and fall into the
general category of metallophilic bonding.69,70 Such metal-
lophilic contacts give rise to the interesting supramolecular
structures and specific photophysical properties of coinage
metal pyrazolates.29,34 The Ag‚‚‚Ag linkages are also im-
portant for the catalytic activity of certain silver adducts.71
As seen from the data presented in Table 4, dimers of
{[3,5-(Ph)2Pz]Ag}3 (obtained from CH2Cl2) have the shortest
intertrimer Ag‚‚‚Ag contact among the silver(I) pyrazolates.
The corresponding Ag‚‚‚Ag separation in {[3-(CF3),5-(CH3)-
Pz]Ag}3 falls at the higher end of the envelope. The
intertrimer Ag‚‚‚Ag separation in the related adduct {[3-
(CF3),5-(But)Pz]Ag}3 is slightly longer than the sum of the
van der Waals radii of two silver atoms. However, the
existence of an attractive force, albeit small, between the
silver centers in this molecule cannot be totally ruled out.
In fact, computational studies indicate that the metallophilic
attractions between coinage metal atoms do not end abruptly
at the van der Waals contact limit.58,70,72,73 For example,
unassisted cuprophiclic interactions could exist when the
Cu‚‚‚Cu distances are even at 4.5 Å (cf. van der Waals
separation of Cu-Cu ) 2.80 Å).73,74
Overall, we describe the synthesis of {[3-(CF3)Pz]Ag}3,
{[3-(CF3),5-(CH3)Pz]Ag}3, {[3-(CF3),5-(Ph)Pz]Ag}3, {[3-
(CF3),5-(But)Pz]Ag}3, and {[3-(C3F7),5-(But)Pz]Ag}3, as well
as two π-acid/base adducts involving silver pyrazolates and
toluene. These compounds represent rare silver(I) complexes
featuring fluorinated pyrazolates. The structurally character-
ized adducts show trinuclear structures. Some of these trimers
aggregate via intertrimer Ag‚‚‚Ag contacts leading to dimers
of trimers or chains of trimers. The steric bulk of the
substituents affects the tendency and nature of aggregation.
It also affects the N-Ag-N angles and the orientation of
pyrazolyl moieties relative to the Ag3 plane. Larger substit-
uents on the pyrazolyl ring 3- and 5-positions lead to
significant distortions in the planar Ag3N6 core. The Ag-N
distances are relatively insensitive to the type of pyrazolyl
ring substituents. The isolation of sandwich molecules with
tight face-to-face contacts between toluene and trinuclear
silver adducts points to the high π-acidic nature of {[3,5-
(CF3)2Pz]Ag}3 and {[3-(C3F7),5-(But)Pz]Ag}3. We are cur-
rently exploring the chemistry and photophysical properties
of these silver adducts.
Table 4. Closest Intertrimer Ag‚‚‚Ag Distances (Å) for Selected
Trinuclear Silver(I) Pyrazolates
closest intertrimer
compound
Ag‚‚‚Ag separation
ref
{[3,5-(Ph)2Pz]Ag}3 (from CH2Cl2)
{[3,5-(i-Pr)2Pz]Ag}3
{[3,5-(i-PrSCH2)2Pz]Ag}3
{[3,5-(i-Pr)2,4-(Br)Pz]Ag}3
{[Pz(IN)]Ag}3
{[3,5-(CF3)2Pz]Ag}3 (from CH2Cl2)
{[2-(3(5)-Pz)Py]Ag}3
{[3,5-(CH3)2Pz]Ag}3
2.971(1)
2.9870(4)
3.041(1)
3.044(5)
3.179(8)
3.2037(4)
3.227(2)
3.230(13)
3.307(13)
3.3553(4)
3.431(4)
3.44
25
39
17
39
36
34
10
20
19
{[3,5-(CF3)2Pz]Ag}3 (from hexane)
{[3-(CF3),5-(CH3)Pz]Ag}3
{[Pz]Ag}3
this work
21
51, 54
sum of Ag-Ag
van der Waals radii
{[3-(CF3),5-(But)Pz]Ag}3
{[3-(C3F7),5-(But)Pz]Ag}3
3.4804(7)
(5.376)
this work
this work
In {[Ag3]′‚[toluene]}∞, the [Ag3]′ and toluene centroids are
separated by 3.11 and 3.16 Å. The closest Ag‚‚‚C(toluene)
distance is 3.143 Å. These distances are remarkably close
despite the large size of the pyrazolyl ring substituents. It is
also interesting to note that the {[Ag3]′‚[toluene]}∞ features
a significantly more-planer less-twisted Ag3N6 metallacycle
compared to that seen in the toluene-free [Ag3]′. For example,
the Ag-N-N-Ag torsion angles of {[Ag3]′‚[toluene]}∞ are
-2.85, -2.64, and 5.39°, while the corresponding angles of
the toluene-free [Ag3]′ are -1.96, -9.90, and 32.17°. It could
be a result of the reduced intertrimer steric interactions in
{[Ag3]′‚[toluene]}∞. Compared to the parent [Ag3]′, the
{[3-(C3F7),5-(But)Pz]Ag}3 units of the {[Ag3]′‚[toluene]}∞
adduct lie relatively far apart. This leaves more space above
and below the {[3-(C3F7),5-(But)Pz]Ag}3 plane for the C3F7
and But substituents to occupy without interfering with the
space demands of the adjacent trimers.
The π-acidic, trinuclear Hg(II) adduct [o-C6F4Hg]3 also
forms sandwich complexes with toluene leading to {[o-C6F4-
Hg]3‚[toluene]}∞ stacks analogous to those of {[Ag3]′‚
[toluene]}∞.59 In {[o-C6F4Hg]3‚[toluene]}∞, the [o-C6F4Hg]3
and toluene centroids are separated by 3.63 and 3.81 Å. The
closest Hg‚‚‚C(toluene) distance is 3.189 Å. Thus, on the
basis of the X-ray data, with consideration of the relatively
smaller van der Waals radius of Hg,54 {[Ag3]′‚[toluene]}∞
appears to have somewhat tighter metal‚‚‚C(toluene) contacts
than those of the {[o-C6F4Hg]‚[toluene]}∞.
Tables 3 and 4 show intratrimer and intertrimer
AgI‚‚‚AgI separations observed for the trinuclear species
herein and for few other silver pyrazolates in the litera-
ture.10,17,19-21,25,34,36,39 The silver atoms of these trinuclear
species are held in close proximity by the bridging pyrazolate
ligands. Thus, the intratrimer Ag‚‚‚Ag distances are primarily
controlled by the pyrazolate bridges and have limited
freedom for variations. On the other hand, close intertrimer
Ag‚‚‚Ag separations, unassisted by bridging ligands or
electrostatics, as seen with {[3-(CF3),5-(CH3)Pz]Ag}3 and
{[Ag3]2‚[toluene]}∞ are noteworthy, represent genuine ex-
(64) Wang, Q.-M.; Mak, T. C. W. J. Am. Chem. Soc. 2001, 123, 7594-
600.
(65) Rawashdeh-Omary, M. A.; Omary, M. A.; Patterson, H. H. J. Am.
Chem. Soc. 2000, 122, 10371-80.
(66) Che, C.-M.; Tse, M.-C.; Chan, M. C. W.; Cheung, K.-K.; Phillips, D.
L.; Leung, K.-H. J. Am. Chem. Soc. 2000, 122, 2464-68.
(67) Kim, S. A.; Kim, Y. J.; Park, K.-M.; Choi, S. N.; Jung, O.-S. Bull.
Korean Chem. Soc. 2005, 26, 181-3.
(68) Jansen, M. Angew. Chem., Int. Ed. Engl. 1987, 99, 1136-49.
(69) Tong, M.-L.; Chen, X.-M.; Ye, B.-H.; Ji, L.-N. Angew. Chem., Int.
Ed. 1999, 38, 2237-40.
(70) Pyykko, P. Chem. ReV. 1997, 97, 597-636.
(71) Cui, Y.; He, C. J. Am. Chem. Soc. 2003, 125, 16202-3.
(72) Carvajal, M. A.; Alvarez, S.; Novoa Juan, J. Chem.sEur. J. 2004,
10, 2117-32.
(73) Hermann, H. L.; Boche, G.; Schwerdtfeger, P. Chem.sEur. J. 2001,
7, 5333-42.
(74) Poblet, J.-M.; Benard, M. Chem. Commun. 1998, 1179-80.
(63) Taylor, T. J.; Burress, C. N.; Pandey, L.; Gabbai, F. P. Dalton Trans.
2006, 4654-4656.
2986 Inorganic Chemistry, Vol. 46, No. 8, 2007

Ag(I) Complexes of Fluorinated Pyrazolates
Supporting Information Available: X-ray crystallographic
data (CIF), ORTEP diagrams, and additional figures for the
structurally characterized compounds presented in this manuscript.
This material is available free of charge via the Internet at
http://pubs.acs.org.
Acknowledgment. Support by the AFPSR through the
SPRING program in Texas and the Robert A. Welch
Foundation (Y-1289) is gratefully acknowledged. We would
also like to acknowledge the contributions of Daniel Been
and Christopher Lam to silver pyrazolate work. They were
supported by the Welch Summer Scholar Program.
IC062374K
Inorganic Chemistry, Vol. 46, No. 8, 2007 2987