Coordination chemistry of the solvated AgI and AuI ions in liquid and aqueous ammonia, trialkyl and triphenyl phosphite, and tri-n-butylphosphine solutions

Article abstract of DOI:10.1021/ic060175v

The coordination chemistry of solvated Ag^I and Au^I ions has been studied in some of the most strong electron-pair donor solvents, liquid and aqueous ammonia, and the P donor solvents triethyl, tri-n-butyl, and triphenyl phosphite and tri-n-butylphosphine. The solvated Ag^I ions have been characterized in solution by means of extended X-ray absorption fine structure (EXAFS), Raman, and ¹⁰⁷Ag NMR spectroscopy and the solid solvates by means of thermogravimetry and EXAFS and Raman spectroscopy. The Ag^I ion is two- and three-coordinated in aqueous and liquid ammonia solutions with mean Ag-N bond distances of 2.15(1) and 2.26(1) A, respectively. The crystal structure of [Ag(NH₃)₃]ClO ₄·0.47 NH₃ (1) reveals a regular trigonal-coplanar coordination around the Ag^I ion with Ag-N bond distances of 2.263(6) A and a Ag...Ag distance of 3.278(2) A separating the complexes. The decomposition products of 1 have been analyzed, and one of them, [Ag(NH₃)₂]ClO₄, has been structurally characterized by means of EXAFS, showing [Ag(NH₃)₂] units connected into chains by double O bridges from perchlorate ions; the Ag...Ag distance is 3.01(1) A. The linear bisamminegold(I) complex, [Au(NH₃)₂]⁺, is predominant in-both liquid and aqueous ammonia solutions, as well as in solid [Au(NH₃) ₂]BF₄, with Au-N bond distances of 2.022(5), 2.025-(5), and 2.026(7) A, respectively. The solvated Ag^I ions are three-coordinated, most probably in triangular fashion, in the P donor solvents with mean Ag-P bond distances of 2.48-2.53 A. The Au^I ions are three-coordinated in triethyl phosphite and tri-n-butylphosphine solutions with mean Au-P bond distances of 2.37(1) and 2.40(1) A, respectively.

Full text of DOI:10.1021/ic060175v

Inorg. Chem. 2006, 45, 6912−6921
Coordination Chemistry of the Solvated AgI and AuI Ions in Liquid and
Aqueous Ammonia, Trialkyl and Triphenyl Phosphite, and
Tri-n-butylphosphine Solutions
Kersti B. Nilsson, Ingmar Persson,* and Vadim G. Kessler
Department of Chemistry, Swedish UniVersity of Agricultural Sciences, P.O. Box 7015,
SE-750 07 Uppsala, Sweden
Received January 31, 2006
The coordination chemistry of solvated AgI and AuI ions has been studied in some of the most strong electron-pair
donor solvents, liquid and aqueous ammonia, and the P donor solvents triethyl, tri-n-butyl, and triphenyl phosphite
and tri-n-butylphosphine. The solvated AgI ions have been characterized in solution by means of extended X-ray
absorption fine structure (EXAFS), Raman, and 107Ag NMR spectroscopy and the solid solvates by means of
thermogravimetry and EXAFS and Raman spectroscopy. The AgI ion is two- and three-coordinated in aqueous and
liquid ammonia solutions with mean Ag
structure of [Ag(NH3)3]ClO4
0.47 NH3 (1) reveals a regular trigonal-coplanar coordination around the AgI ion with
Ag N bond distances of 2.263(6) Å and a Ag‚‚‚Ag distance of 3.278(2) Å separating the complexes. The
−N bond distances of 2.15(1) and 2.26(1) Å, respectively. The crystal
‚
−
decomposition products of 1 have been analyzed, and one of them, [Ag(NH3)2]ClO4, has been structurally characterized
by means of EXAFS, showing [Ag(NH3)2] units connected into chains by double O bridges from perchlorate ions;
the Ag‚‚‚Ag distance is 3.01(1) Å. The linear bisamminegold(I) complex, [Au(NH3)2]+, is predominant in both liquid
and aqueous ammonia solutions, as well as in solid [Au(NH3)2]BF4, with Au
(5), and 2.026(7) Å, respectively. The solvated AgI ions are three-coordinated, most probably in triangular fashion,
in the P donor solvents with mean Ag P bond distances of 2.48
2.53 Å. The AuI ions are three-coordinated in
P bond distances of 2.37(1) and 2.40(1) Å,
−N bond distances of 2.022(5), 2.025-
−
−
triethyl phosphite and tri-n-butylphosphine solutions with mean Au
−
respectively.
Introduction
4 decades later the stepwise stability constants to log K1 )
3.315 and log K2 ) 3.915.6 Thus, the second complex is
somewhat stronger than the first one, and the bisammine-
silver(I) complex is strongly dominating (>99.8%) in solu-
tions with a free ammonia concentration of 0.01 mmol‚dm-3
or more (calculated from the stability constants reported by
Bjerrum6). These stability constants have been reproduced
by a large number of research groups.7 In addition to the
linear complex, Hancock and Bjerrum reported independently
much later the presence of a very weak trisamminesilver(I)
Ammonia is the N donor solvent possessing the strongest
electron-pair donor properties, DS ) 56,1 in comparison with
12 and 38 for acetonitrile and pyridine, respectively.2 The
AgI ion is regarded as a typical soft electron-pair acceptor,
and very stable silver(I)-ammonia complexes are formed
in aqueous solution. The formation of amminesilver(I)
complexes in aqueous ammonia was studied very early.3 The
stability constant of the second complex, [Ag(NH3)2]+, log
â2, was determined soon thereafter to ca. 7.2, depending on
the ionic medium and temperature,4,5 and Bjerrum reported
(4) Bodla¨nder, G.; Fittig, G. Z. Phys. Chem. 1902, 39, 597.
(5) von Euler, H. Ber. Bunsen-Ges. 1903, 36, 1854, 2878, 3400.
(6) Bjerrum, J. Thesis; Report 1957; P. Haase & Son: Copenhagen,
Denmark, 1941.
* To whom correspondence should be addressed. E-mail:
ingmar.persson@kemi.slu.se.
(1) Nilsson, K. B.; Maliarik, M.; Persson, I.; Sandstro¨m, M., unpublished
data. New Raman data on HgI2 in liquid ammonia reveals ν(Hg-I)
) 132 cm-1, giving DS ) 56.
(7) Sille´n, L. G.; Martell, A. E. Stability Constants of Metal-Ion
Complexes, Special Publication Nos. 17 and 25; The Chemical
Society: London, 1964 and 1971. Pettit, L. IUPAC Chemical Series
No. 22; IUPAC Stability Constant Database; Academic Software:
Timble, Otley, Yorks, U.K., 2000, and references cited therein.
Homepage: www.acadsoft.co.uk.
(2) Sandstro¨m, M.; Persson, P.; Persson, I. Acta Chem. Scand. 1990, 44,
653.
(3) Berthelot, D.; Delepine, M. Compt. Rend. 1899, 129, 326.
6912 Inorganic Chemistry, Vol. 45, No. 17, 2006
10.1021/ic060175v CCC: $33.50
© 2006 American Chemical Society
Published on Web 07/26/2006

Coordination Chemistry of the SolWated AgI and AuI Ions
of a tetrahedrally coordinated ammonia-solvated AgI ion in
liquid ammonia has been supported by an extended X-ray
absorption fine structure (EXAFS) study, reporting a mean
Ag-N bond distance of 2.31 Å.19
The structures of a number of silver(I) triphenylphosphine
complexes in the solid state have been reported.20a The
isolated tris- and tetrakis(triarylphosphine)silver(I) complexes
are trigonal, with a very slight pyramidal distortion,21 and
tetrahedral,21a,22 with mean Ag-P bond distances of 2.517
(mean of 6 structures) and 2.654 Å (12 structures), respec-
tively. Five structures containing a bis(triphenylphosphine)-
silver(I) complex have been reported; the mean Ag-P bond
distance is 2.411 Å.23 To our knowledge, no structures of
isolated tris- and tetrakis(trialkylphosphine)silver(I) com-
plexes have been reported in the solid state.20a Two linear
bis(trialkylphosphine)silver(I) complexes, bis(trimethylphos-
phine)-24 and bis[tris(cyanoethylphosphine)]silver(I),25 with
mean Ag-P bond distances of 2.377 and 2.383 Å, respec-
tively, have been structurally characterized. This shows that
the Ag-P bonds are shorter, and most probably also stronger,
to trialkylphosphines than to triphenylphosphine, supported
by complex formation studies.26
Figure 1. Complex distribution function of the silver(I)-ammonia system
in water.
complex in a concentrated aqueous ammonia solution, log
K3 ) -0.76 and -1.60, respectively.8,9 The very small
stability constant of the third complex shows that it is never
dominating, ca. 0.55 and 5.2% at log [NH3] ) 0.0 and 1.0,
respectively, using Bjerrum’s values of K1-K36,9 (Figure 1).
The ammonia-solvated CuI ion is three-coordinated in
trigonal fashion in liquid ammonia,10 with a structure very
similar to that of the trisamminecopper(I) complex in the
solid nitrate salt.11 It can be assumed that the ammonia-
solvated AgI ion is three-coordinated in the same way as
the CuI ion in liquid ammonia because the AgI ion, as well
as the CuI ion, forms a weak third complex in aqueous
solution7 and the fact that the AgI ion in solid [Ag(NH3)3]-
NO3, precipitated from liquid ammonia, has a trigonal-planar
configuration. The Ag-N bond distance in solid [Ag(NH3)3]-
NO3 is 2.281(7) Å.11 On the other hand, a linear bisammine-
silver(I) complex is expected to dominate strongly in aqueous
ammonia solutions because the third complex is very weak
(Figure 1). The crystal structures of [Ag(NH3)2][Ag(NO2)2],
[Ag(NH3)2]NO3, [Ag(NH3)2]2SO4, [Ag(NH3)2]ClO4, catena-
(bis(µ3-hexamethylenetetraamine)disilver(I) bis(bisammine-
silver(I)) 1,2,4,5,-benzenetetracarboxylate trihydrate, and
bis(bisamminesilver(I)) bis(biuretato-N,N′)nickel(II) hexahy-
drate all contain a linear bisamminesilver(I) complex with
mean Ag-N bond distances of 2.115,12 2.15(2),11 2.110(3),13
2.11-2.16 (two different phases at ambient and low tem-
perature),14 2.121,15 and 2.122 Å,16 respectively. The mean
Ag-N bond distance in an aqueous ammonia solution of
silver(I) nitrate, where the bisamminesilver(I) complex is
strongly dominating, is reported from a large-angle X-ray
scattering (LAXS) study to be 2.22(2) Å.17 This is much
longer than that found for the same complex in the solid
state, and it seems very doubtful that this Ag-N bond
distance is correct.
(17) Maeda, M.; Maegawa, Y.; Yamaguchi, T.; Othaki, H. Bull. Chem.
Soc. Jpn. 1979, 52, 2545.
(18) Gans, P.; Gill, J. B. J. Chem. Soc., Dalton Trans. 1976, 779.
(19) Yamaguchi, T.; Wakita, H.; Nomura, M. J. Chem. Soc., Chem.
Commun. 1988, 433.
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Kennard, O.; Motherwell, W. D. S.; Rodgers, J. R.; Watson, D. G.
The Cambridge Crystallographic Data Centre: computer-based search,
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Structure Data Base, release 04/2; National Institute of Standards and
Technology, Fachinformationszentrum: Karlsruhe, Germany.
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Gans and Gill interpreted their Raman results of the AgI
complex in liquid ammonia as four-coordination.18 The view
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Patmore, N. J.; Pourke, J. P.; Ruggiero, G. D.; Weller, A. S. J. Am.
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Inorganic Chemistry, Vol. 45, No. 17, 2006 6913

Nilsson et al.
Only one structure of a silver(I) triphenyl phosphite solvate
complex is reported.27 In this compound, bis(µ-nitrato)bis-
[bis(triphenyl phosphite)silver(I)], the AgI ion is surrounded
by two P atoms and two nitrate O atoms in a distorted
tetrahedral arrangement with Ag-P bond distances of
2.402-2.404 Å and a P-Ag-P angle of 147.9°.
the bis(trialkylphosphine)- and bis(triphenylphosphine)gold-
(I) complexes and for the tris(trialkylphosphine)-36 and tris-
(triphenylphosphine)gold(I) complexes, respectively. The
surprisingly large difference in the Au-P bond distance
between tris- and tetrakis(triphenylphosphine)gold(I) com-
plexes is probably caused by steric hindrance in the latter.
The aim of this study is to describe the coordination
chemistry of the AgI and AuI ions in some of the strongest
electron-pair donor solvents known, ammonia and P donor
solvents.1,2 1:1 salts of monovalent metal ions are the only
ones that can be dissolved and dissociated in P donor
solvents; the low permittivity of these solvents prevents
dissociation of salts containing di- or trivalent ions. The
structure of the solvated CuI ion in strong electron-pair donor
solvents displays frequently a lower coordination number
than is geometrically allowed because of the soft bonding
character of both the metal ion and solvent.10 This paper
reports the coordination chemistry of the even softer AgI and
AuI ions as a continuation of the CuI study. A literature
survey of ammonia-, phosphite-, and phosphine-solvated CuI,
AgI, and AuI ions in the solid state and the results in the
present study in solution describe the coordination chemistry
in these very strong electron-pair acceptor-donor systems.
The structural studies in solution are performed with EXAFS,
and a crystallographic determination of solid [Ag(NH3)3]-
ClO4‚0.47NH3 is reported as well. 107Ag NMR and Raman
spectroscopy and thermogravimetric analysis (TGA) mea-
surements are reported to further characterize the complexes
synthesized and/or structurally characterized in solution.
AuI is only stable in solvents coordinating through N, P,
or S, while in O donor solvents, AuIII is the most stable
oxidation state. The coordination of the solvated AuI ion in
the N donor solvents pyridine and acetonitrile is assumed to
be tetrahedral with mean Au-N bond distances of 2.16(2)
and 2.19(2) Å, respectively,28 while the AuI solvate com-
plexes in solvents with the softer and more polarizable P, S,
and ammonia N donor atoms are linear.20 AuI forms
extremely stable complexes with ammonia in aqueous
+
solution, log â2 ) 26.5.29 The [Au(NH3)2 ] complex is most
probably linear in aqueous solution, as was found in the solid
[Au(NH3)2]Br salt, with Au-N bond distances of 2.01(2)-
2.03(2) Å.30 Several bisamminegold(I) complexes have been
synthesized, but the structural information is limited.30,31
The structures of the isolated bis-, tris-, and tetrakis-
(triphenylphosphine)gold(I) complexes in the solid state are
linear,32 trigonal,33 and tetrahedral33a,34 with mean Ag-P bond
distances of 2.312, 2.387, and 2.634 Å, respectively. The
structures of a large number of linear bis(trialkylphosphine)-
gold(I) complexes are reported,20a with a mean Au-P bond
distance of 2.309 Å, while no structure has been reported
for any tris(trialkylphosphine)gold(I) complex. The structures
of four tetrakis(1,3,5-triaza-7-phosphaadmantane)gold(I) com-
plexes have a surprisingly short mean Au-P bond distance,
2.397 Å.35 The mean Au-P bond distances are the same for
Experimental Section
Solvents. Liquid ammonia was distilled from 25% aqueous
ammonia (analytical grade, Merck) and used within some hours.
The distillation procedure has been described in detail elsewhere.16
Trialkyl and triphenyl phosphites and tri-n-butylphosphine (reagent
grade, Sigma-Aldrich) were used without further purification.
Chemicals and Preparation of Solutions. Solid trisammine-
silver(I) perchlorate, [Ag(NH3)3]ClO4‚0.47 NH3 (1), was prepared
by dissolving anhydrous silver perchlorate in liquid ammonia at
ca. 220 K, and the temperature was slowly elevated to boil off the
ammonia. The white crystals formed were recrystallized once from
liquid ammonia before crystallographic examination. This com-
pound is very unstable outside the mother-liquid or ammonia
atmosphere and was stored in a refrigerator in an ammonia
atmosphere prior to analysis. The grinding of these crystals in order
to perform a homogeneous mixture with boron nitride (BN) for
EXAFS measurements caused a rapid decomposition to bisam-
minesilver(I) perchlorate, [Ag(NH3)2]ClO4 (2). When the mixture
was heated to 433 K, a further decrease of the ammonia content
occurred and monoamminesilver(I) perchlorate, Ag(NH3)ClO4, was
formed. Anhydrous silver(I) nitrate, AgNO3 (Fluka), and silver(I)
chloride, AgCl (Fluka), were dried in an oven before use.
(26) (a) Ahrland, S.; Hulte´n, F.; Persson, I. Acta Chem. Scand., Ser. A
1986, 40, 595. (b) Hulte´n, F.; Persson, I. Inorg. Chim Acta 1987, 128,
43.
(27) Ahlgren, M.; Pakkanen, T.; Tahvainen, I. Acta Chem. Scand., Ser. A
1985, 39, 651.
(28) Ahrland, S.; Nilsson, K.; Persson, I.; Yuchi, A.; Penner-Hahn, J. E.
Inorg. Chem. 1989, 28, 1833.
(29) Skibsted, L.; Bjerrum, J. Acta Chem. Scand., Ser. A 1974, 28, 740,
764.
(30) Mingos, D. M. P.; Yau, J.; Menzer, S.; Williams, D. J. J. Chem. Soc.,
Dalton Trans. 1995, 319.
(31) Vicente, J.; Chicote, M.; Guerrero, R.; Jones, P. G.; Ram´ırez de
Arellano, M. Inorg. Chem. 1997, 36, 4438.
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Soc., Dalton Trans. 1983, 809. (b) Baenziger, N. C.; Bennett, W. E.;
Soboroff, D. M.; O’Donnell, P. S.; Doyle, J. R. Polyhedron 1998, 17,
2379. (c) Baukova, T. V.; Kravtsov, D. N.; Kuz’mina, L. G.;
Dvortsova, N. V.; Porai-Koshits, M. A.; Perevalova, E. G. J.
Organomet. Chem. 1989, 465, 372. (d) Baukova, T. V.; Ellert, O. G.;
Kuz’mina, L. G.; Dvortsova, N. V.; Lemenovskii, D. A.; Rubezhov,
A. Z. MendeleeV Commun. 1991, 22. (e) Staples, R. J.; King, C.; Khan,
M. N. I.; Winpenny, R. E. P.; Fackler, J. P., Jr. Acta Crystallogr.,
Sect. C 1993, 49, 472. (f) Alonso, P. J.; Cerrada, E.; Garin, J.; Gimeno,
M. C.; Laguna, A.; Laguna, M.; Jones, P. G. Synth. Met. 1993, 55,
1772. (g) Marsch, R. E.; Spek, A. L. Acta Crystallogr., Sect. B 2001,
57, 800. (h) Anderson, S.; Mullica, D. F.; Sappenfield, E. L.; Stone,
F. G. A. Organometallics 1995, 14, 3516. (i) Wang, J.-C. Acta
Crystallogr., Sect. C 1996, 52, 611.
(33) (a) Jones, P. G. Chem. Commun. 1980, 1031. (b) Beurskens, P. T.;
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1995, 14, 3497. (e) Olbrich, F.; Lagow, R. J. Z. Anorg. Allg. Chem.
1995, 621, 1929.
Solid bisamminegold(I) tetrafluoroborate, [Au(NH3)2]BF4 (3),
was prepared by dissolving ca. 0.5 g of metallic Au powder (99.9%,
Aldrich) in a 100-cm3 dry acetonitrile solution of nitrosyl tetrafluo-
roborate, NOBF4 (Merck), ca. 0.5 g, at room temperature as
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1996, 35, 16.
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6914 Inorganic Chemistry, Vol. 45, No. 17, 2006

Coordination Chemistry of the SolWated AgI and AuI Ions
Table 1. Compositions of the Studied Solutions
Table 2. Crystallographic Data for 1 at 295 K
concentration/
compound
empirical formula
fw
cryst size/mm
wavelength/Å
cryst syst
space group
a/Å
[Ag(NH3)3]ClO4‚0.47NH3
sample
mol‚dm-3
methoda
H10.41ClN3.47O4Ag
266.415
AgCl in NH3(aq)
AgNO3 in NH3(aq)
AgClO4 in NH3(l)
AgNO3 in NH3(l)
AgNO3 in Me2NCHS
AgClO4 in P(OCH3)3
AgClO4 in P(OC2H5)3
AgClO4 in P(OC4H9)3
AgClO4 in P(OC6H5)3
AgClO4 in P(C4H9)3
[Au(NH3)2]BF4 in NH3(aq)
[Au(NH3)2]BF4 in NH3(l)
AuBF4 in P(OC2H5)3
0.7
2.0
0.6
0.44
0.5
0.5
0.7
0.61
0.15
0.5
E
R
E, R
R
N
N
E
E
E
E, N
E
E, R
E
0.20 × 0.25 × 0.40
0.710 73
hexagonal
P3h1c (No. 163)
8.237(3)
6.555(3)
385.1(3)
c/Å
V/Å3
Z
2
Dc/g‚cm-3
µ(Mo KR)/mm-1
abs corrn
transmission factors
F(000)
2.375
2.936
empirical method
0.384, 0.5913
272
0.6
sat. sol./0.6
0.35
a N ) 107Ag NMR, E ) EXAFS, L ) LAXS, and R ) Raman
θ
max/deg
h, k, l
24.96
(9, -9 - +7, (7
214
156
3.99
91.5
spectroscopy.
indep reflns
reflns with I > 2σ(I)
R
completeness (%) to θ ) 24.96°
refinement method
described elsewhere.37 The volume of this solution was reduced to
ca. 10 cm3 and mixed with freshly distilled water-free liquid
ammonia. When the liquid ammonia had evaporated, yellow crystals
of 3 were formed. It is important to stress that all chemicals must
be very dry during the synthesis; otherwise, a black precipitate is
immediately formed. Weighed amounts of 3 were dissolved in the
solvents studied; the prepared [Au(NH3)2]+ complexes are perfectly
stable in aqueous systems.
int/%
full-matrix least squares on F 2
214/19/32
1.174
R1 ) 0.0339
wR2 ) 0.0809
R1 ) 0.01175
wR2 ) 0.0857
1.2(2)
data/restraints/param
GOF on F 2
final R indices (λ > 2σ)a
R indices (all data)a
extinction coeff
The concentrations of the studied solutions are summarized in
Table 1.
largest diff peak and hole/e‚Å-3
+0.238 to -0.190
a Definition of R (SHELXTL): R ) ∑||Fo| -|Fc||/∑|Fo|; Rw ) [∑[w(|Fo|
EXAFS: Data Collection. Ag K-edge and Au LIII-edge X-ray
absorption spectra were recorded at the wiggler beam line 4-1 at
the Stanford Synchrotron Radiation Laboratory (SSRL). The
EXAFS station was equipped with a Si[220] double-crystal mono-
chromator. SSRL operated at 3.0 GeV and a maximum current of
100 mA. The data collections were performed in transmission mode,
except for AuI in aqueous ammonia and tri-n-butylphosphine
solutions, where fluorescence mode, using a Lytle detector with a
flow of Ar, was applied. The experiments were performed at
ambient temperature, except for the measurement of the AuI solvate
in a liquid ammonia solution, when the temperature of the sample
was kept at about 200 K. Higher order harmonics were reduced by
detuning the second monochromator to 70 and 50% of the
maximum intensity at the end of the scans for Ag and Au,
respectively. The solid compounds were diluted in BN to give an
edge step of about one unit in the logarithmic intensity ratio and
kept in sample cells made of 1-mm brass frames with Mylar tape
windows. The phosphite and phosphine solutions of AgI and AuI
were measured in sample cells with 1.5-2-mm Vitone spacers and
35-55-µm glass windows. The liquid and aqueous ammonia
solutions of silver(I) perchlorate were kept in 1.5-mL airtight glass
vials with an outer diameter of ca. 10 mm. The liquid ammonia
solution of AuI was contained in a 2-mm Ti spacer with 35-55-
µm glass windows, equipped with a Cu rod, which was dipped
into a methanol/liquid N2 cooling mixture of ca. 175 K as described
elsewhere.10 The temperature was slowly increasing during the
experiment because of evaporation of the liquid N2. The energy
scales of the X-ray absorption spectra were calibrated by assigning
the first inflection point of the K edge of a Ag foil to 25 514 eV
and that of the LIII edge of a Au foil to 11 919 eV.38 For each
- |Fc|)2/∑(w|Fo|2]1/2; R1 ) ∑||Fo| - |Fc||/∑|Fo|; wR2 ) (∑[w(Fo2 - Fc2)2]/
∑[w(Fo )2]]1/2
.
2
sample, 3-6 scans were averaged. The EXAFSPAK39 program
package was used for the primary data treatment.
EXAFS: Data Analysis. The data analyses were performed by
means of the GNXAS code in order to get the best possible splines.
The GNXAS code is based on the calculation of the EXAFS signal
and a subsequent refinement of the structural parameters.40,41 The
GNXAS method accounts for multiple scattering (MS) paths, with
correct treatment of the configurational average of all of the MS
signals to allow fitting of correlated distances and bond distance
variances (Debye-Waller factors). A correct description of the first
coordination sphere of the studied complex has to account for
asymmetry in the distribution of the ion-solvent distances.42,43
Therefore, the Ag-N and Au-N two-body signals associated with
the first coordination shells were modeled with Γ-like distribution
functions, which depend on four parameters, namely, the coordina-
tion number N, the average distance R, the mean-square variation
σ, and the skewness â. The â term is related to the third cumulant
C3 through the relation C3 ) σ3â, and R is the first moment of the
function 4π ∫g(r)2 dr. It is important to stress that R is the average
distance and not the position of the maximum of the distribution
(Rm).
The standard deviations given for the refined parameters in
Tables 3 and 4 are obtained from k2-weighted least-squares
refinements of the EXAFS function ø(k) and do not include
systematic errors of the measurements. These statistical error
(39) George, G. N.; Pickering, I. J. EXAFSPAKsA Suite of Computer
Programs for Analysis of X-ray Absorption Spectra; SSRL: Stanford,
CA, 1993.
(40) Filipponi, A.; Di Cicco, A.; Natoli, C. R. Phys. ReV. B 1995, 52, 15122.
(41) Filipponi, A.; Di Cicco, A. Phys. ReV. B 1995, 52, 15135.
(42) Filipponi, A. J. Phys.: Condens. Matter 1994, 6, 8415.
(43) Hedin, L.; Lundqvist, B. I. J. Phys. C: Solid State Phys. 1971, 4,
2064.
(37) Bergerhoff, G. Z. Anorg. Allg. Chem. 1964, 327, 139.
(38) Thompson, A.; Attwood, D.; Gullikson, E.; Howells, M.; Kim, K.-J.;
Kirz, J.; Kortright, J.; Lindau, I.; Pianatta, P.; Robinson, A.; Scofield,
J.; Underwood, J.; Vaughan, D.; Williams, G.; Winick, H. X-ray Data
Booklet; LBNL/PUB-490 Revision 2; Lawrence Berkeley National
Laboratory: Berkeley, CA, 2001.
Inorganic Chemistry, Vol. 45, No. 17, 2006 6915

Nilsson et al.
Table 3. Mean Bond Distances, d/Å, Number of Distances, N, Debye-Waller Factor Coefficients, σ2/Å2, Third Cumulant Factors Describing the
2
Asymmetry, Bond Angles Calculated from MS Pathways, θ/deg, C3 ) âσ3/Å3, the Amplitude Reduction Factor, So , the Threshold Energy, Eo/eV, and
the Least-squares Value of the Refinement, F, of the Ammonia, Trialkyl and Triphenyl Phosphite, and Tri-n-butylphosphine Solvated AgI Ions in
Solution and the Solids [Ag(NH3)2]ClO4 and [Ag(P(OC6H5)3)3]ClO4 As Determined by EXAFS at Room Temperature
scattering
2
sample
path
Ag-N
Ag‚‚‚H
Ag-N-H
N-Ag-N
Ag-N
Ag- -O
N
d
σ2
θ
C3
So
Eo
F
[Ag(NH3)2]+ in NH3(aq)
room temperature
2
6
6
2
3
1
3
2
2
2
2
2
2
2
2
3
1
9
9
3
3
1
9
9
3
3
1
9
9
3
3
9
9
3
3
9
9
9
3
2.148(2)
2.67(2)
0.0013(2)
0.0092(2)
5.6 × 10-6
0.855
25 519.2
4.7 × 10-9
1.3 × 10-5
109.6(1.0)
180.0(0.5)
[Ag(NH3)3]+ in NH3(l)
room temperature
2.265(5)
2.88(2)
0.0145(8)
0.015(2)
4.8 × 10-6
1.1 × 10-5
0.835
0.875
25 519.3
25 519.6
1.8 × 10-8
1.7 × 10-7
N-Ag-N
Ag-N
120.0(0.8)
[Ag(NH3)2]ClO4(s)
(heated to 333 K, s1)
2.150(5)
3.015(4)
6.021(10)
3.20(3)
2.151(5)
3.012(4)
6.015(10)
3.21(3)
2.483(3)
2.74(3)
1.385(3)
3.32(2)
4.32(2)
2.513(2)
2.90(4)
1.380(3)
3.29(2)
4.32(2)
2.485(2)
2.88(3)
1.417(3)
3.34(2)
4.34(2)
2.495(2)
1.380(5)
3.35(2)
4.32(2)
2.528(4)
1.805(3)
2.76(3)
3.58(1)
4.46(2)
0.0122(7)
0.0038(4)
0.0120(10)
0.055(4)
0.0120(7)
0.0038(4)
0.0115(10)
0.054(4)
0.0058(2)
0.0042(4)
0.015(2)
0.053(4)
0.0116(6)
0.0079(2)
0.0113(5)
0.015(2)
0.053(4)
0.0264(5)
0.0117(3)
0.030(5)
0.0098(4)
0.042(4)
0.033(2)
0.0071(2)
0.0140(6)
0.032(3)
0.011(1)
0.0020(2)
0.0126(3)
0.022(4)
0.0050(5)
0.017(1)
3.6 × 10-6
6.2 × 10-5
0
Ag- -Ag
Ag- -Ag
Ag-O
1.5 × 10-5
3.5 × 10-6
6.0 × 10-5
0
[Ag(NH3)2]ClO4(s)
(ground at RT, s2)
Ag-N
0.877
0.885
25 519.6
25 517.7
1.7 × 10-7
1.7 × 10-7
Ag- -Ag
Ag- -Ag
Ag-O
1.5 × 10-5
1.1 × 10-5
1.4 × 10-5
2.1 × 10-6
[Ag(P(OC2H5)3)3]+
room temperature
Ag-P
Ag- -O
P-O
Ag-P-O
P-Ag-P
Ag-P
Ag- -O
P-O
Ag-P-O
P-Ag-P
Ag-P
Ag- -O
P-O
115.4(1.4)
121.0(1.0)
[Ag(P(OC4H9)3)3]+
room temperature
4.0 × 10-5
5.4 × 10-5
3.2 × 10-6
0.915
0.874
25 517.5
25 518.3
7.1 × 10-8
1.1 × 10-7
112.1(1.4)
119.5(1.0)
[Ag(P(OC6H5)3)3]+
room temperature
8.2 × 10-5
5.2 × 10-5
1.6 × 10-6
Ag-P-O
P-Ag-P
Ag-P
115.4(1.0)
121.9(1.0)
[Ag(P(OC6H5)3)3]ClO4(s)
room temperature
5.2 × 10-5
3.3 × 10-6
0.886
0.896
25 518.2
25 516.2
1.4 × 10-7
3.8 × 10-7
P-O
Ag-P-O
P-Ag-P
Ag-P
116.6(1.7)
119.9(1.1)
[Ag(P(C4H9)3)3]+
room temperature
3.7 × 10-6
4.5 × 10-6
4.3 × 10-5
P-C
Ag- -O
Ag-P-C
P-Ag-P
110.3(8)
123.9(1.2)
Table 4. Mean Bond Distances, d/Å, Number of Distances, N, Debye-Waller Factor Coefficients, σ2/Å2, Third Cumulant Factors Describing the
2
Asymmetry, C3 ) âσ3/Å3, the Amplitude Reduction Factor, So , the Threshold Energy, Eo/eV, and the Least-Squares Value of the Refinement, F, of the
Ammonia, Triethyl Phosphite, and Tri-n-butylphosphine Solvated AuI Ions in Solution and Solid [Au(NH3)2]BF4 As Determined by EXAFSa
scattering
2
sample
path
Au-N
N-H
Au-N-H
N-Au-N
Au-N
Au- -H
N-Au-N
Au-N
N-H
Au-N-H
N-Au-N
Au-P
P-O
Au-P-O
P-Ag-P
Au-P
P-C
Au-P-C
P-Au-P
N
d
σ2
θ
C3
So
Eo
F
[Au(NH3)2]+ in NH3(aq)
room temperature
2
6
6
1
2
6
1
2
6
6
1
3
9
9
3
3
9
9
3
2.022(2)
1.095(5)
0.0026(2)
0.0038(3)
0
0.813
11 922.2
2.1 × 10-8
2.8 × 10-6
109.9(1)
180.1(1)
[Au(NH3)2]+ in NH3(l)
ca. 200 K
2.026(3)
2.58(2)
0.0019(2)
0.005(2)
0
0
0.839
0.829
11 922.3
11 922.2
8.1 × 10-7
2.1 × 10-8
180.0(1)
[Au(NH3)2]BF4 (s)
room temperature
2.025(2)
1.087(5)
0.0032(2)
0.0018(3)
0
2.1 × 10-6
113(1)
180.0(1)
[Au(P(OC2H5)3)3]+
room temperature
2.367(3)
1.383(4)
0.0073(4)
0.0040(4)
3.2 × 10-5
5.3 × 10-6
0.835
0.802
11 922.4
11 921.6
8.1 × 10-8
3.2 × 10-8
115.3(9)
124.5(8)
[Au(P(C4H9)3)3]+
room temperature
2.399(3)
1.895(5)
0.0082(4)
0.0082(6)
6.5 × 10-5
4.2 × 10-6
115.5(8)
120.8(0.5)
a At the presence of asymmetry, the position of the peak maximum, Rm/Å, has been calculated.
estimates provide a measure of the precision of the results and allow
reasonable comparisons, e.g., of the significance of relative shifts
in the distances. However, the variations in the refined parameters,
including the shift in the Eo value (for which k ) 0), using different
6916 Inorganic Chemistry, Vol. 45, No. 17, 2006

Coordination Chemistry of the SolWated AgI and AuI Ions
models and data ranges, indicate that the absolute accuracy of the
distances given for the separate complexes is within (0.01-0.02
Å for well-defined interactions. The “standard deviations” given
in the text have been increased accordingly to include estimated
additional effects of systematic errors.
Single-Crystal X-ray Diffraction. Data were collected with a
Bruker SMART CCD 1 k diffractometer at 295 ( 1 K.44 The
structure was solved by standard direct methods in the SHELXTL
program package45 and refined by full-matrix least squares isotro-
pically on F 2 and finally in anisotropic approximation. H atoms
were detected in difference Fourier syntheses and refined using a
riding model. All calculations were performed with the SHELXTL
programs in PC version (version 5.3).45 Selected crystal and
experimental data are summarized in Table 2. The atomic coordi-
nates and bond distances and angles are available as CIFs in the
Supporting Information.
present in the crystal lattice. The final model presented in
this paper was therefore refined in the group P3h1c. Selected
crystallographic data and details of structural refinement are
given in Table 2. The determination of the structure of the
solid solvate of silver perchlorate, crystallized from liquid
ammonia, 1, reveals a regular trigonal-coplanar coordination,
N-Ag-N ) 120 °, around the AgI ion with a Ag-N bond
distance of 2.263(6) Å (CIF file in the Supporting Informa-
tion). The Ag complexes are arranged in linear chains with
a fairly short Ag‚‚‚Ag distance in a manner almost identical
with that previously reported in the corresponding nitrate
salt17 (Figure 2). The Ag‚‚‚Ag distance in 1, 3.278(2) Å, is
slightly longer than that in the nitrate salt, probably because
of the presence of the larger and more spacious perchlorate
anion, while the Ag-N bond distances in the two compounds
are similar. The four H atoms on the ammonia N atoms are
due to symmetric restrictions and thereby have the occupancy
Raman Spectroscopy. Raman spectra of the samples were
measured by means of a Fourier transform (FT)-Raman module
FRA106/S in combination with a Bruker IFS66/S FT-IR spectrom-
eter equipped with a FT-Raman accessory. The 1064-nm line from
a Nd:YAG laser was used to irradiate the samples, and 10-200
3
of /4. The intrachain metal-metal distances are caused by
H bonds and not by bonding interactions between the AgI
ions, as concluded by Zachwieja and Jacobs in the case of
the nitrate salt.11 The perchlorate anions are severely
disordered. The structure contains partially occupied am-
monia positions in the potentially empty spaces occurring
as a result of the the presence of the comparably large
perchlorate anions. This may explain the assumption made
by Gans and Gill of the formation of the compound with
the empirical formula [Ag(NH3)4]ClO4.18
scans were collected at a spectral bandwidth of 2-4 cm-1
.
Thermogravimetry. TGA studies were performed on a Perkin-
Elmer TGA7. The amount of sample used in each experiment was
5-7 mg, and heating was performed in an open Pt crucible at a
rate of 10 K‚min-1 in an Ar atmosphere in the range 293-873 K
and in a N2 atmosphere in the range 293-673 K.
Atomic Absorption Spectrophotometry (AAS). The Ag content
in degraded 1 was determined by dissolving the samples in 5%
HNO3 and analyzing the solution using AAS on a Perkin-Elmer
AAnalyst 100.
Degradation Products of 1. When 1 was heated to 333
K for 10 min or ground in a mortar prior to the EXAFS
analysis, the structure did decompose to essentially [Ag-
(NH3)2]ClO4. The EXAFS data analyses showed the presence
of a Ag-N bond distance of 2.15(1) Å, typical for a linear
complex (see above), and a short Ag‚‚‚Ag distance of 3.012-
(10) Å, in both samples (Table 3 and Figure 3). The XANES
spectra show a distinct shoulder on the edge typical for linear
Ag complexes (Figure S1 in the Supporting Information).
The solid-state structures of two modifications of [Ag(NH3)2]-
ClO4 have been reported with transition temperatures at 200-
210 K; the Ag‚‚‚Ag distances in the low- and high-
temperature phases are 3.020 and 3.0885 Å, respectively.14
Thus, the Ag‚‚‚Ag distance in the decomposition products
is very similar to that observed in the low-temperature phase.
When the same sample was ground and heated to 433 K for
10 min, the product was essentially [Ag(NH3)]ClO4, with a
Ag content of 48.8% (expt), 48.1% (theor). No structure
determination of [Ag(NH3)]ClO4 was performed. The fit of
the EXAFS data is given in Figure 3 and that of the Fourier
transforms in Figure S2 in the Supporting Information.
TGAs were performed on the crystals of 1, and two areas
of “steady state” could be seen in the temperature range 293-
673 K, one at ca. 403 K, when the lattice ammonia is lost
(97.2% expt; 97.7% theor), and one at ca. 673 K, after
deammoniation when only one ammonia ligand or less is
left (82.6% expt; 84.6% theor). The curve smoothly declines,
and two ammonia ligands are lost, without distinctive
plateaus (Figure S3 in the Supporting Information), leaving
a complex with one ammonia molecule bound. Ag AAS
analyses performed on ground 1 at ambient temperature are
107Ag and 109Ag NMR Spectroscopy. The 107Ag and 109Ag NMR
spectra were recorded at 16.20 and 18.62 MHz, respectively, on a
Bruker 400 DRX spectrometer equipped with a multinuclear BBO
probe. Because the chemical shift is dependent on both the anion
and concentration, the results are given relative to an infinite D2O
solution of AgI.46 The spectral width was 16 234-32 467 Hz, and
the number of data points in each data acquisition was 131 000. A
pulse width of 6 µs (90° pulse) was used, with a recycle delay of
32 s, and the number of scans was 16-64 for samples with high
concentration and 1900-7400 for samples with low concentration.
The samples were kept in cylindrical tubes with an outer diameter
of 5 mm at 303 K. The liquid ammonia solutions of silver
perchlorate and nitrate were prepared at 220 K and then transferred
into airtight 5-mm NMR tubes, Wilmad, kept under pressure. 10%
CD3CN or D2O was used as a lock signal.
Results and Discussion
Crystal Structure of 1. The space groups P3h1c and P63/
mmc were considered for the solution and refinement for
the structure of 1 on the basis of extinction analysis. The
total distribution of intensities in the experiment was,
however, in favor of space group P3h1c, as well as the
extinctions, leading the P3h1c space group to have markedly
lower R factors compared to the P63/mmc group. Application
of the higher symmetry P63/mmc group was, in addition, not
permitting a proper placement of the additional ammonia
(44) Bruker SMART and SAINT, area detector control and integration
software; Bruker Analytical X-ray Systems: Madison, WI, 1995.
(45) Sheldrick, G. M. Acta Crystallogr., Sect. A 1990, 46, 467.
(46) Burges, C. W.; Koschmieder, R.; Sahm, W.; Schwenk, A. Z.
Naturforsch., A: Phys. Phys. Chem., Kosmophys. 1973, 28, 1753.
Inorganic Chemistry, Vol. 45, No. 17, 2006 6917

Nilsson et al.
Figure 2. Crystal structure of 1.
in liquid ammonia, most probably because of the low
permittivity of the solvent, while the salts are completely
dissociated in aqueous ammonia. The large Debye-Waller
+
parameter of the trigonal Ag(NH3)3 complex in liquid
ammonia may indicate that the complex has nonequidistant
+
Ag-N bonds. The high symmetry of the trigonal Ag(NH3)3
complex in the solid state may be caused by a random
distribution of distorted complexes in a way similar to that
described for CuII complexes found to be regularly octahedral
from crystallography.47 The fairly long Ag-N bond distance
+
of 2.22(2) Å in the linear Ag(NH3)2 complex in aqueous
ammonia reported from a LAXS study17 could not be
confirmed by EXAFS in this study. The Ag-N bond distance
of 2.15(1) Å in the bisamminesilver(I) ion in an aqueous
ammonia solution (Table 3) is within the range of distances
found in the crystal structure determinations of the linear
bisamminesilver(I) complexes (see Introduction). The mean
Ag-N bond distance of 2.26(1) Å in liquid-ammonia-
solvated trisamminesilver(I) is close to the one found in the
crystal structures of [Ag(NH3)3]NO311 and 1; see Introduction
and Table 3. Thus, the change in the mean coordination
number when the AgI ion is transferred from aqueous to
liquid ammonia is caused by an increased ammonia activity;
see Figure 1. Theoretical studies of the ammonia-solvated
AgI ion in silver(I)-ammonia clusters in the gaseous phase
show a very fine balance between two- and three-coordinated
species, with linear complexes somewhat more stable than
the planar three-coordinated ones.48 This is in contradiction
to the results in this and previous studies when the ammonia
activity is high; see Introduction.
Figure 3. k2-weighted EXAFS data of experimental (thin line) and
theoretical (thick line) data of the ammonia-solvated AgI ion in liquid and
aqueous ammonia and of solid [Ag(NH3)2]ClO4, formed after being heated
to 333 K for 10 min (s1) and grinding at room temperature (s2). Data regions
excluded in the refinements are shown with dotted thin lines in the
experimental data.
in agreement with the composition of [Ag(NH3)2]ClO4; silver
content, 44.6% (expt), 44.7% (theor).
AgI in Liquid and Aqueous Ammonia. EXAFS data of
liquid and aqueous ammonia solutions of silver(I) perchlorate
(Figures 3 and S2 in the Supporting Information and Table
3) reveal that the ammonia-solvated AgI ion has different
geometric arrangements in the two solvents. The mean
Ag-N bond distance in aqueous ammonia (log [NH3] )
1.12; Figure 1) is much shorter than that in liquid ammonia,
2.15(1) and 2.26(1) Å, respectively, strongly indicating linear
and trigonal configurations, respectively. The fit of the
experimental data of the silver(I) perchlorate solution in
liquid ammonia is improved by the introduction of a very
long Ag-O distance. Ion-pair formation seems to take place
(47) Fox, B. S.; Beyer, M. K.; Bondybey, V. E. J. Am. Chem. Soc. 2002,
124, 13613.
(48) Persson, I.; Persson, P.; Sandstro¨m, M.; Ullstro¨m, A.-S. J. Chem. Soc.,
Dalton Trans. 2002, 1256.
6918 Inorganic Chemistry, Vol. 45, No. 17, 2006

Coordination Chemistry of the SolWated AgI and AuI Ions
Figure 4. k2-weighted EXAFS data of experimental (thin line) and theoretical (thick line) data of the triethyl, tri-n-butyl and triphenyl phosphite, and
tri-n-butylphosphine solvated AgI ions in solution. Data regions excluded in the refinements are shown with dotted thin lines in the experimental data.
AgI in Triethyl, Tri-n-butyl, and Triphenyl Phosphite
and Tri-n-butylphosphine Solutions. The mean Ag-P
bond distances of 2.48-2.51 Å in the solvates of AgI in
trialkyl and triphenyl phosphite solutions (Table 3) cor-
respond to a trigonal configuration geometry around the AgI
ion (see Introduction). The mean Ag-P bond distance in
tri-n-butylphosphine, 2.53(1) Å, is slightly longer than that
in the phosphites. This longer Ag-P bond distance is
expected because the electron cloud on phosphines is slightly
larger than that on phosphites because of the electron-
withdrawing effects of the O atoms in phosphites. The Ag-
Figure 5. k2-weighted EXAFS data of experimental (thin line) and
P-O angles are 112-116° for the phosphite silver(I)
complexes, and the Ag-P-C angle in the tris(tri-n-bu-
tylphosphine)silver(I) complex is ca. 110°. The fit of the
experimental data of the silver(I) perchlorate solution in tri-
n-butylphosphine is improved by the introduction of a very
long Ag-O distance. An ion-pair formation is not surprising
in tri-n-butylphosphine because of its low permittivity. The
structural parameters of the solvated AgI ions in trialkyl and
triphenyl phosphite and tri-n-butylphosphine as determined
by EXAFS are summarized in Table 3; the fits to the EXAFS
data are given in Figure 4 and those of the Fourier transforms
in Figure S2 in the Supporting Information.
AuI in Liquid and Aqueous Ammonia. EXAFS data of
3 containing the bisamminegold(I) ion, [Au(NH3)2]+, gives
a Au-N bond distance of 2.025(5) Å, and the Au-N bond
distances in the AuI solvates in aqueous and liquid ammonia
are 2.022(5) and 2.026(7) Å, respectively (Table 4). Con-
sequently, the linear bisamminegold(I) ion is strongly
predominating in both liquid and aqueous ammonia solutions
and with the same Au-N bond distance as that in solid [Au-
(NH3)2]Br.29 The bisamminegold(I) solvate in a liquid
ammonia solution has a N-Ag-N angle of 180.0(5)° (Table
4); the N-Au-N angle is 178.7(8)° in [Au(NH3)2]Br because
of H bonds from the ammonia H atoms to the bromide ions.29
In solid [Au(NH3)2]Br, there are also Au- - -Au distances at
3.414(1) Å, but the EXAFS data on 3 reveal no such
distances. The results are summarized in Table 4; the fittings
of the EXAFS data are given in Figure 5, including the
individual contributions in Figure S4 in the Supporting
theoretical (thick line) data of the ammonia-solvated AuI ion in liquid and
aqueous ammonia and of solid [Au(NH3)2]BF4. Data regions excluded in
the refinements are shown with dotted thin lines in the experimental data.
Information, the fittings of the Fourier transforms are given
in Figure S5 in the Supporting Information, and the absorp-
tion edges are given in Figure S6 in the Supporting
Information. Attempts to perform single-crystal X-ray crys-
tallography on 3 have been made before but failed because
of photosensitive and unstable crystals.29 The GNXAS
program allows the omission of erroneous data points or data
regions, e.g., due to glitches, in the refinements of structural
parameters, and such data points cannot be deleted or
replaced. These regions are marked with dots in the
experimental data functions in Figures 5 and S4 in the
Supporting Information.
AuI in Triethyl Phosphite and Tri-n-butylphosphine
Solutions. The mean Au-P bond distances in the AuI
solvates of triethyl phosphite and tri-n-butylphosphine are
2.37(1) and 2.40(1) Å, respectively (Table 4 and Figures 6
and S5 in the Supporting Information). The mean Au-P
bond lengths fit very well with three-coordination (see
Introduction), and the more expanded electron cloud on the
phosphine than on the phosphite (see the Ag section above)
explains the longer Au-P bond distance in the phosphine.
The Au-P-O and Au-P-C angles are both 115°.
Raman Spectroscopy of Ammonia-Solvated AgI and
AuI Ions. The wavenumbers recorded for the bisammine-
silver(I) complex formed in an aqueous ammonia solution,
Inorganic Chemistry, Vol. 45, No. 17, 2006 6919

Nilsson et al.
Table 5. Raman Bands and Assignments of the AgI and AuI Complexes Formed in Aqueous and Liquid Ammonia, in the Solid State and Solution
-
M-NH3
NO3-/ClO4-/BF4
ammonia
2δ(NH3)deg
sample
νsym
ν1
ν4
ν2
δ(NH3)deg
ν(NH3)sym
ν(NH3)as
[Ag(NH3)2]ClO4(s)
378
370
238
317
385
934
1048
934
1044
920
625
1616
627
459
1611
3182
3292
3310
3300
3298
3300
3300
3358
[Ag(NH3)2]NO3 in NH3(aq)
[Ag(NH3)2]ClO4 in NH3(l)
[Ag(NH3)3]NO3 in NH3(l)
[Au(NH3)2]BF4 in NH3(l)
NH3(l)
460
1636
3215
3215
3215
3215
3377
3380
3381
3381
1641
1642
and the degraded form [Ag(NH3)2]ClO4 produced from liquid
ammonia, are in agreement with a previous study of
bisamminesilver(I) perchlorate in solution and bisammine-
silver(I) nitrate in the solid state, with symmetric Ag-N
stretching wavenumbers present at 369 and 372 cm-1,
respectively.49 The spectrum of the linear bisamminesilver-
(I) ion in aqueous ammonia is not very well-resolved, and
the corresponding stretching wavenumber is found, as in
previous studies, at ca. 370 cm-1.50 The assignments of the
recorded Raman wavenumbers are listed in Table 5. The
results from the measurements of silver(I) nitrate in liquid
ammonia show a weak Ag-N symmetric stretching wave-
number at ca. 317 cm-1, close to the wavenumber reported
by Lundeen and Tobias,50 who curve-fitted their peak into
two wavenumbers, 296 and 329 cm-1. Gans and Gill reported
a Ag-N symmetric stretching wavenumber of silver nitrate
in liquid ammonia at 263 cm-1.18 We have also studied a
liquid ammonia solution of silver(I) perchlorate where a fairly
strong band at 238 cm-1 has been assigned to the Ag-N
symmetric stretching wavenumber, for which the lower
wavenumber may be an effect of the ion-pair formation
mentioned above.
Figure 6. k2-weighted EXAFS data of experimental (solid) and theoretical
(dashed) data of the triethyl phosphite and tri-n-butylphosphine solvated
AuI ions in solution.
Figure 7. 107Ag NMR shifts of the solvated AgI ion in different solvents.
*
109Ag measurement in ref 57.
107Ag NMR of Solvated AgI Ions. The 107Ag NMR
chemical shifts of a number of AgI solvates have been
recorded in order to further characterize the Ag solvate
complexes studied; the shifts are given relative to an intrinsic
solution of silver nitrate in heavy water, D2O (Figure 7).
Because the change in shift is rather large between various
AgI solvates, the difference depends on the environment of
the Ag nucleus. The largest shielding is observed in the
solvates with the strongest Ag-solvate bonds, the most bulky
solvent molecules, and high coordination number. There is
a significant shift of the ammonia-solvated AgI ions in
aqueous and liquid ammonia. Because the shift is dependent
on the concentration of the AgI ions,51 three different
concentrations of silver nitrate in aqueous ammonia, 0.44-
6.0 mol‚dm-3, were measured. However, the range in shift
is narrow, 430-450 ppm, and the difference is not large
enough to intervene with shifts of AgI in other solvents.
Because the 107Ag NMR shift is also dependent on the anion,
both silver nitrate and silver perchlorate in liquid ammonia
were investigated. The difference in the shift of 0.44
mol‚dm-3 solutions was negligible.
Coordination Chemistry of the Monovalent Group 11
Metal Ions in Soft Donor Solvents. The coordination
chemistry of the monovalent group 11 metal ions in the
solvents with the strongest electron-pair donor properties,
liquid and aqueous ammonia, trialkyl and triaryl phosphites,
and trialkyl- and triarylphosphines, shows that the maximum
allowed coordination numbers possible are not observed in
solution but sometimes in the solid state (Table 6).
The ammonia-solvated CuI, AgI, and AuI ions are all linear
in aqueous solution, while a trigonal configuration is
observed in liquid ammonia for CuI and AgI because of
higher ammonia activity; the linear configuration of bisam-
minegold(I) is so stable that any higher complexes are not
formed, even in neat liquid ammonia.
Triarylphosphine complexes of CuI, AgI, and AuI in linear,
trigonal, and tetrahedral configurations are reported in the
solid state (Table 6). Linear and tetrahedral copper(I)
trialkylphosphine complexes are reported in the solid state,
while for AgI only linear and for AuI only linear and
triangular trialkylphosphine complexes are reported so far
(Table 6). The M-P bond distances in the tetrahedral
triarylphosphine complexes are much longer than those in
the corresponding trialkylphosphine complexes and are
comparable to the corresponding linear and trigonal tri-
arylphosphine complexes. This is certainly due to the large
cone angle of triphenylphosphine (145°),53 which causes the
M-P bond distance to be largely controlled by the ligand-
(49) Miles, M. G.; Patterson, J. H.; Hobbs, C. W.; Hopper, M. J.; Overend,
J.; Tobias, R. S. Inorg. Chem. 1968, 7, 1721.
(50) Lundeen, J. W.; Tobias, R. S. J. Chem. Phys. 1975, 63, 924.
(51) Jucker, K.; Sahm, W.; Schwenk, A. Z. Naturforsch. A: Phys., Phys.
Chem., Kosmophys. 1976, 31, 1532.
(52) Lamble, G.; Moen, A.; Nicholson, D. J. Chem. Soc., Faraday Trans.
1994, 90, 2211.
6920 Inorganic Chemistry, Vol. 45, No. 17, 2006

Coordination Chemistry of the SolWated AgI and AuI Ions
Table 6. Summary of Mean M-L Bond Distances (in Å) in Solvate Complexes of the Monovalent Group 11 Metal Ions and the Strong Electron-Pair
Donor Solvents Ammonia, Triaryl and Trialkyl Phosphite, and Triaryl- and Trialkylphosphine in the Solid State and in the Neat Solvent (Italics) in
Basically Linear (2), Trigonal (3), and Tetrahedral (4) Configuration
CN ) 2
CN ) 3
CN ) 2
CN ) 3
CN ) 4
CN ) 3
CN ) 4
P(OR)3
2.242/1a
NH3
NH3
PØ3
PR3
PØ3
PR3
N/A
PØ3
PR3
P(OØ)3
P(OR)3
N/A
Cu+
Ag+
Au+
1.963/3a
1.88b,c
N/A
2.228/1a
2.201/4a
2.385/3a
2.311/20a
2.294/8a
2.525/4a
2.387/8a
2.564/2a
2.271/11a
N/A
2.00d,e
2.272/1a,f
2.26d,e
N/A
2.132/15a
2.148b,d
2.020/1a,d
2.025b,d,e
2.433/8a
N/A
2.649/12a
2.533/2c
N/A
2.481g
2.485d
N/A
N/A
N/A
N/A
N/A
2.528d
2.421/1a
2.399d
2.308/15a
N/A
2.367d
a Number of solid-state structures in the mean value; see the Supporting Information for details. b Aqueous ammonia. c Reference 52. d This work, EXAFS
data. e Liquid ammonia. f Mean of the results from ref 11 and 1. g Mean of the results from refs 21c and 21d. h Mean of the results from the triethyl and
tri-n-butyl phosphite solutions.
ligand repulsion. The tri-n-alkylphosphine ligands have
smaller cone angles and the alkyl groups are less space
demanding than the phenyl groups, and any steric restrictions
at the coordination of four ligands around the group 11 metal
ions seem not to exist. On the other hand, tricyclohexy-
lphosphine and trialkylphosphines with large branched alkyl
chains have larger cone angles than triphenylphosphine and
are thereby even more space-demanding.
The relativistic effects of especially AuI causes that the
size of the monovalent group 11 ion to increase in the order
Cu+ < Au+ < Ag+ in steps of ca. 0.1 Å (Table 6).54,55 The
coordination numbers of the solvate complexes in solution
(neat solvents) are lower than those geometrically possible.
This shows that the configuration is largely controlled by
the molecule orbitals on the metal ions in solvate complexes
dominated by covalent metal-ligand bonds.
the TGAs, and from Prof. Bo Liedberg, Department of
Physics and Measurements, Linko¨ping University, for the
use of the Raman and IR spectrometers. We gratefully
acknowledge the financial support given to these investiga-
tions by the Swedish Research Council. SSRL is gratefully
acknowledged for allocation of beam time and laboratory
facilities at our disposal. SSRL is operated by the Department
of Energy, Office of Basic Energy Sciences. The SSRL
Biotechnology Program is supported by the National Insti-
tutes of Health, National Center for Research Resources,
Biomedical Technology Program, and by the Department of
Energy, Office of Biological and Environmental Research.
Supporting Information Available: 107Ag NMR shifts of AgI
solvates in solution, TGA raw data, normalized XANES spectra
of studied AgI and AuI complexes, Fourier transforms of AgI and
AuI complexes, EXAFS data of AuI complexes analyzed with the
GNXAS program package, and a summary of the solid-state
structures containing ammonia, trialkyl- and triarylphosphine, and
trialkyl and triaryl phosphite solvated CuI, AgI, and AuI ions. The
reference manual to Table 6 is given in Tables S2-S4 including
mean bond distances and references. This material is available free
of charge via the Internet at http://pubs.acs.org.
Acknowledgment. We are grateful for the support from
Rolf Andersson for the recording of Ag NMR data, from
Dr. Mats Johnsson, Stockholm University, for carrying out
(53) Tolman, C. A. Chem. ReV. 1977, 77, 313.
(54) Ahrland, S.; Nilsson, K.; Persson, I.; Yuchi, A.; Penner-Hahn, J. E.
Inorg. Chem. 1989, 28, 1833.
(55) Bayler, A.; Schier, A.; Bowmaker, G. A.; Schmidbaur, H. J. Am. Chem.
Soc. 1996, 118, 7006.
IC060175V
Inorganic Chemistry, Vol. 45, No. 17, 2006 6921