Unusual silver coordination by mono-carboxylate utilization of a poly-carboxylate anion, solid-state structures of silver-tetrachlorophthalate with phthalazine and amine ligands

Article abstract of DOI:10.1016/j.ica.2007.08.031

Silver carboxylate coordination with the tetrachlorophthalate anion, in combination with neutral donor ligands, has been found to deviate from other known poly-carboxylate complexes. Both complexes reported here, bis-[tetrachlorophthalato-silver phthalazine] and bis-[ammino-tetrachlorophthato-silver di-ammino-silver], utilize mixed carboxylate bonding types for silver coordination. In the case of the phthalazine ligand, both chelating and monodentate carboxylates form the framework for the oligomeric structure. In the case of the ammine ligand, one carboxylate forms a monodentate connection to a silver-ammine group, while the other is simply involved with hydrogen bonding to lock in a [(Ag-NH₃)₂-Ag-NH₃] substructure with an adjacent tetrachlorophthalato-silver unit. Both structures exhibit supramolecular connections via hydrogen bonding and π-π interactions.

Full text of DOI:10.1016/j.ica.2007.08.031

Available online at www.sciencedirect.com
Inorganica Chimica Acta 361 (2008) 1357–1362
www.elsevier.com/locate/ica
Unusual silver coordination by mono-carboxylate utilization
of a poly-carboxylate anion, solid-state structures
of silver-tetrachlorophthalate with phthalazine and amine ligands
a,
b
D.R. Whitcomb *, M. Rajeswaran
a
Carestream Health, Inc., 1 Imation Way, Oakdale, MN 55128, United States
Eastman Kodak Company, 1999 Lake Avenue, Rochester, NY 14650-2106, United States
b
Received 12 July 2007; received in revised form 27 August 2007; accepted 27 August 2007
Available online 4 September 2007
Abstract
Silver carboxylate coordination with the tetrachlorophthalate anion, in combination with neutral donor ligands, has been found to
deviate from other known poly-carboxylate complexes. Both complexes reported here, bis-[tetrachlorophthalato-silver phthalazine] and
bis-[ammino-tetrachlorophthato-silver di-ammino-silver], utilize mixed carboxylate bonding types for silver coordination. In the case of
the phthalazine ligand, both chelating and monodentate carboxylates form the framework for the oligomeric structure. In the case of the
ammine ligand, one carboxylate forms a monodentate connection to a silver-ammine group, while the other is simply involved with
hydrogen bonding to lock in a [(Ag–NH3)2–Ag–NH3] substructure with an adjacent tetrachlorophthalato-silver unit. Both structures
exhibit supramolecular connections via hydrogen bonding and p–p interactions.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: Silver complexes; Mono-carboxylate; Phthalate; Structure; Polymer; Dimer; X-ray crystal structures
1. Introduction
matic amine ligands, such as phthalazine (PHZ, Fig. 1),
have been reported to form rearranged coordination poly-
mers based on a silver-containing ring, ½AgPHZ22þꢀ dimer
units in [Ag(PHZ)PHZ(NO3)]2 [2], and the same dimer in
silver carboxylate complexes [(Ag(PHZ))1-2(carboxylate)]
[3]. In these latter cases, the PHZ ligand dominates the
structural motif, while the carboxylate anions remain par-
tially coordinated to the silver by bridging the six-mem-
bered ring dimers. Changing to simpler ammine ligands,
such as ammonia, enables many silver carboxylate com-
plexes to crystallize well enough for solid-state structure
characterization, previously inhibited by their generally
poor solubility [4]. Approximately half of the structures
reported from using this labile-volatile ligand approach
incorporate the ammine into the structure well enough that
it remains part of the complex to fill out the silver coordina-
tion sphere [5]. In our continuing efforts to further under-
stand silver coordination chemistry [1d,1e,1f,3], we now
report the contrasting cases of two quite different silver
Many silver carboxylates have been structurally well
characterized [1]. In nearly all of these cases, the silver
adopts an eight-membered ring configuration that is poly-
merized by additional, long Ag–O bonding contacts with
neighboring units. In addition, one of the most interesting
features in these complexes is the Ag–Ag separation, which
˚
is typically found to be 2.8–3.0 A. This distance encom-
passes the normal bond distance for metallic silver,
˚
2.889 A, and suggests metal–metal bonding interactions
are likely present.
Silver carboxylate complexes containing neutral donor
ligands completely change the polymeric structural units,
including the Ag–Ag separation distance. For example, aro-
*
Corresponding author. Tel.: +1 651 393 1467; fax: +1 651 393 1120.
E-mail address: david.whitcomb@carestreamhealth.com (D.R. Whit-
comb).
0020-1693/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2007.08.031

1358
D.R. Whitcomb, M. Rajeswaran / Inorganica Chimica Acta 361 (2008) 1357–1362
Single-crystal diffraction data were collected at 298 K
Cl
Cl
O
O
using Nonius Kappa CCD [7]. Data reductions were per-
formed using Denzo-SMN [8]. The unit cells for 1 and 2
were determined to be monoclinic, and the space groups
were uniquely determined from systematic absences to be
P21/c. The structure of 2 was solved by direct methods
using Bruker SHELXTL [9] and that of 1 by using the
‘‘dual-space recycling method’’ in the XM [10] module of
the Bruker SHELXTL [9] package. Both structures were
refined by full-matrix, least-squares on F2 with anisotropic
displacement parameters for the non-hydrogen atoms
using Bruker SHELXTL [9]. Hydrogen atoms were included
in idealized positions with isotropic displacement parame-
ters. The structures refined to final residuals of
R1 = 0.0496 and 0.0516 for 1 and 2, respectively. The R-
value (0.1593) for all data in 2 is high, which we attribute
to a large amount of weak data, since out of 3665 observed
reflections only 1705 are >2r. In the structure of 1, there
are three molecules of AgPHZ Æ HTCPA in the asymmetric
unit and two water molecules of solvation in the lattice.
Three of the carboxylic oxygen atoms in the 1 structure
were disordered and were left isotropic. Details of cell data,
data collection, and structure refinement are summarized in
Table 1.
Cl
Cl
OH
OH
N
N
Fig. 1. TCPA, PHZ.
carboxylate complexes, resulting from the reaction of di-sil-
ver-tetrachlorophthalate (from tetrachlorophthalic acid,
Fig. 1) with neutral donor ligands. Unlike the usual struc-
tures, when PHZ is the neutral donor, the complex does
not polymerize by carboxylate bridging, and forms a bis-
[tetrachlorophthalato-silver phthalazine] complex (1). With
the NH3 ligand, an unusual mixed structure of bis-[ammino-
tetrachlorophthalato-silver di-ammino-silver] (2), results. In
1, monomeric complexes are formed, and in 2, the ammine is
incorporated into the complex both as a route to fill out the
silver coordination sphere and also in a way that incorpo-
rates AgðNH3Þ2þ units held together by N–Hꢁ ꢁ ꢁO hydrogen
bonds. This latter structure arrangement is not unusual for
other anionic silver ammine complexes [6].
We report here the preparation and X-ray structure
characterization of two unusual silver complexes con-
structed from these nitrogen-based ligands, which exhibit
deviations in the anticipated structures relative to those
previously reported. The phthalazine complex, [AgPHZ Æ
HTCPA]2(H2O)2, is a stable complex having a silver coor-
dination sphere similar to other known silver phthalazine
carboxylate complexes but differs by virtue of its single car-
boxylate-coordination participation. The second, [Ag(N-
H3)2Ag(NH3)TCPA], also is limited to one of the
carboxylates in the siþlver coordination sphere by incorpo-
rating the AgðNH3Þ2 moiety via hydrogen bonding. The
unusual bonding configuration resulting from these ligands
may be useful for designing new silver-based materials.
3. Results and discussion
3.1. bis-[Tetrachlorophthalato-silver phthalazine] di-hydrate
The silver complex containing both phthalazine and
TCPA, having the molecular formula [AgPHZ Æ HTCPA]2-
(H2O)2, is a very stable, colorless, crystalline solid. Unlike
most silver carboxylate complexes containing multiple car-
boxylate groups, the carboxylate coordination is non-sym-
metric, Figs. 2 and 3.
It can be seen that the fundamental coordination sphere
consists of a six-membered N–N–Ag–N–N–Ag ring with
normal Ag–N bond distances, Figs. 2 and 3.
2. Experimental
This six-membered ring is typical for silver phthalazine
complexes [2,3]. In addition, it is notable that a simple,
mono-dentate TCPA is bound to the silver, with Ag–O
bond distances, Table 2, ranging 2.23(2)–2.532(7) A. Most
silver carboxylates show additional bonding with the car-
Preparation of 1: [AgPHZ Æ HTCPA]2(H2O)2: To 0.13 g
Ag2TCPA (previously prepared from a stoichiometric reac-
tion of AgNO3 and Na2TCPA in water) in a 4 oz bottle was
placed a 0.5 oz bottle containing 45 mg PHZ. Water was
added to both bottles until the top of the inner bottle
was just covered. The large bottle was sealed, and the
reagents were allowed to stand undisturbed for two weeks.
Colorless needles grew on the outside of the inner bottle,
which were collected and air dried.
˚
bonyl of the carboxylate group. While the long Agꢁ ꢁ ꢁO at
˚
2.739(16) A distance is not uncommonly long, the asym-
metric arrangement of the carboxylate relative to the silver
suggests that it is not participating in a chelating conforma-
tion. The net result of the silver connection points in this
complex produces a network structure, Fig. 4.
Preparation of 2: [Ag(NH3)2Ag(NH3)TCPA]2(H2O)2:
To 1.7 g Ag2TCPA was added 5 g H2O, followed by con-
centrated NH4OH dropwise until a clear solution was
obtained. A slight discoloration was removed by filtering
through 1.6 lm glass fiber filter paper, and the filtrate
was allowed open to the atmosphere to slowly lose NH3.
A colorless, crystalline solid was obtained, which was dec-
anted and air dried.
Silver poly-carboxylate complexes reported in the litera-
ture are found with a silver ion associated with each car-
boxylate [3a,4b,4c,12]; the single exception is the
structure for silver-maleate [4b]. The Agꢁ ꢁ ꢁAg distance in
the six-membered ring of the [AgPHZ Æ HTCPA]2(H2O)2
˚
title complex is 3.2417(9) A, which is well outside the range
˚
normally reported for a Ag–Ag bond (2.8–3.0 A [13]), even
˚
though it is within the Van der Waals radii of 3.44 A [14]. It

D.R. Whitcomb, M. Rajeswaran / Inorganica Chimica Acta 361 (2008) 1357–1362
1359
Table 1
Crystal data and structure refinement
Complex 1 [AgPHZ Æ HTCPA]3(H2O)2
Complex 2 [Ag(NH3)2Ag(NH3)TCPA]2(H2O)2
Empirical formula
Formula weight
Temperature (K)
C48H18Ag3Cl12N6O14
1651.69
293(2)
C8H9Ag2Cl4N3O5
584.72
293(2)
˚
Wavelength (A)
0.71073
0.71073
Crystal system
Space group
Unit cell dimensions
monoclinic
P21=c
monoclinic
P21=c
˚
a (A)
18.9878(3)
8.10050(10)
36.1155(7)
98.9130(10)
5487.87(15)
4
8.9823(3)
27.2419(8)
7.0743(2)
111.2920(10)
1612.89(8)
4
˚
b (A)
˚
c (A)
b (ꢁ)
Volume (A )
3
˚
Z
Dcalc (Mg/m3)
1.999
2.408
Absorption coefficient
1.717
3.113
(mmꢂ1
)
F(000)
3220
0.25 · 0.10 · 0.10
3.03–22.47
1120
0.40 · 0.17 · 0.05
3.31–27.49
Crystal size (mm3)
Theta range for data
collection (ꢁ)
Index ranges
ꢂ20 6 h 6 20, ꢂ7 6 k 6 8, ꢂ37 6 l 6 38
ꢂ11 6 h 6 11, ꢂ35 6 k 6 35, ꢂ9 6 l 6 9
Reflections collected
Independent reflections
Completeness to
25029
17965
6907 [Rint = 0.0446]
96.5%
3665 [Rint = 0.1300]
99.1%
theta = 27.49ꢁ
Absorption correction
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2r(I)]
R indices (all data)
Extinction coefficient
Largest diffraction peak and
multiscan [11]
multiscan [11]
full-matrix, least-squares on F2
6907/0/747
full-matrix, least-squares on F2
3665/0/203
1.055
0.927
R1 = 0.0496, wR2 = 0.1470
R1 = 0.0833, wR2 = 0.1730
R1 = 0.0516, wR2 = 0.1134
R1 = 0.1593, wR2 = 0.1407
0.0012(2)
1.088 and ꢂ1.103
0.815 and ꢂ0.696
ꢂ3
˚
hole (e A
)
is noteworthy that this structure also contains hydrogen
bonding between the HTCPA and the lattice water (for
example, O14–O2 and O13–O1 at 2.622 A and 2.682 A,
respectively).
Cl
Cl
Cl
˚
˚
O
O
OH
Cl
N
N
O
Cl
Cl
Ag
Ag
O
O
O
N
N
Cl
HO
Table 2
Comparison of selected Ag–N, Ag–O, and Ag–Ag distances in AgTCPA
complexes
Cl
[AgPHZ Æ HTCPA]2(H2O)2
[Ag(NH3)2Ag(NH3)TCPA]2(H2O)2
Fig. 2. Molecular structure of [AgPHZ Æ HTCPA]2(H2O)2 (lattice H2O
not shown).
Ag(1)–N(5)
Ag(1)–N(6)
Ag(2)–N(1)
Ag(2)–N(4)
Ag(3)–N(2)
Ag(3)–N(3)
Ag(2)–O(80)#1
Ag(2)–O(8)#1
Ag(2)–O(5)
Ag(3)–O(4)
Ag(3)–O(3)
Ag(1)–O(12)
Ag(2)–Ag(3)
2.216(6)
2.337(6)
2.284(6)
2.308(6)
2.205(6)
2.252(6)
2.23(2)
2.367(16)
2.390(6)
2.462(7)
2.532(7)
2.331(6)
3.2417(9)
Ag(1)–N(1)
Ag(1)–N(2)
Ag(2)–N(3)
2.119(6)
2.125(6)
2.150(5)
Ag(2)–O(2)
2.173(4)
Ag(2)–Ag(2)#1
Ag(2)–Ag(1)#1
Ag(1)–Ag(2)
3.1578(12)
3.2757(8)
3.3657(9)
Fig. 3. Bonding pattern in [AgPHZ Æ HTCPA]2(H2O)2.

1360
D.R. Whitcomb, M. Rajeswaran / Inorganica Chimica Acta 361 (2008) 1357–1362
Fig. 4. Network connections in [AgPHZ Æ HTCPA]2(H2O)2.
Ordinarily, this dimeric complex, despite its high molec-
is shown schematically in Fig. 5 and as an Ortep drawing in
Fig. 6.
The two different silver ammine units are connected
together via extensive hydrogen bonding into a cubic core
capped with TCPA ligands, Fig. 7.
ular weight, might be expected to exhibit some water solu-
bility. However, extensive p–p interactions between the
aromatic rings of the PHZ and TCPA, and especially
˚
between PHZ and PHZ at 3.307 A, are well within the nor-
mal range observed for these types of interactions in the lit-
erature [15].
Cl
Cl
OH
O
H3N Ag NH3
3.2. bis-[Ammino-tetrachlorophthato-silver di-ammino-
silver] di-hydrate
Cl
Cl
O
O
O
Cl
Cl
NH3
Ag
Cl
Cl
Silver carboxylates typically exhibit poor solubility [16],
which inhibits the preparation of crystals suitable for sin-
gle-crystal X-ray structure analysis. One approach to
enhance the prospects of forming single crystals is slow
crystallization of the water-soluble ammine complex as a
result of the ammine equilibrium evolving free, volatile
ammonia [4]. That is, an equilibrium is established that
takes advantage of the reversible dissociation of the NH3
ligand and its volatility:
O
O
Ag
H3N
H3N
Ag
NH3
OH
Fig. 5. Molecular structure of [Ag(NH3)2Ag(NH3)TCPA]2(H2O)2 (lattice
water not shown).
ðNH3Þ2AgðO2CRÞðaqÞ $ ðNH3ÞAgðO2CRÞðaqÞ
þ NH3ðgÞ
$ AgðO2CRÞðsÞ þ NH3ðgÞ
ð1Þ
Under these circumstances, the ammine may be completely
eliminated from the silver coordination sphere [4], but of-
ten times it is retained as part of the isolated complex [5].
In the case of Ag2TCPA, when recrystallized from NH3,
the ammine ligand is retained in the structure. What is un-
ique, however, is how the ammine is incorporated in this
case to form a bis-[ammino-tetrachlorophthalato-silver
di-ammino-silver] complex. That is, this unusual complex
consists of a combination of two completely different silver
structures – that of a diammine silver group superimposed
on an ammino-silver carboxylate framework. The structure
Fig. 6. Formula unit of [Ag(NH3)2Ag(NH3)TCPA]2 Æ (H2O)2.

D.R. Whitcomb, M. Rajeswaran / Inorganica Chimica Acta 361 (2008) 1357–1362
1361
The second component of 2, the ammino-silver tetra-
chlorophthalate, is very reminiscent of [NH3AgCBBA]
[5c], where CBBA is 2-(4-chloro-benzoyl)-benzoic acid. In
that case, a simple mono-silver-carboxylate structure is
observed that is analogous to the TCPA component of
˚
the title complex. The 2.119(6)–2.150(5) A Ag–N bond
lengths compare well to the two-coordinate silver in the
˚
[NH3AgCBBA] complex, 2.098(2) A. In the literature, the
˚
only relevant Ag–Nammine bond distances are 2.158(5) A
for a 2,3-pyrazinedicarboxylato-di-silver(I) ammine com-
˚
plex [4c] and 2.154(5) A for the p-nitrobenzoato-silver(I)
ammine complex [5a]. Simple [Ag(NH3)2]+ complexes, on
Fig. 7. Silver ammine connections in [Ag(NH3)2Ag(NH3)TCPA]2 Æ H2O2.
the other hand, exhibit Ag–Nammine bond lengths of 2.11–
˚
2.18 A [6d,6e]. The carboxylate functionality in 2 shows
The two distinct silver coordination spheres can be trea-
ted independently for discussion purposes. The simplest
component, AgðNH3Þ2þ, is a two coordinate, nearly linearly
bound silver, which is quite normal when compared to the
˚
the Ag–O bond to be a robust 2.173(4) A, compared to
the [NH3AgCBBA] complex, where these bonds are normal
but significantly longer at 2.309(2) and 2.468(2) A. The
shorter bond length for 2 is expected for a stable Ag–O
bond, and the longer Ag–O bond is not unusual, which
range up to 2.7 A [1,4].
There is one more significant point that is worth men-
tioning regarding 2. In order to achieve charge balance,
both carboxylates of the TCPA group must be anionic,
not just the one involved with silver coordination. As a
˚
other AgðNH3Þ (Xꢂ) structures reported in the literature
þ
2
[6]. In these cases, Xꢂ is NO3ꢂ; NO2ꢂ, and SO42þꢂ, all pro-
˚
duce the same linear structure in the AgðNH3Þ2 unit and
with only small crystal lattice differences when changing
the anion. The solid-state structure of these complexes is
the result of extended N–Hꢁ ꢁ ꢁO bonding, which connects
the AgðNH3Þ2þ units into an extended structure. The hydro-
þ
˚
result, each of the AgðNH3Þ2 groups, which have no sig-
gen bonding in these complexes range 2.971(4)–3.0229(4) A,
˚
nificant Ag–O contact distances, is held in place by N–H
bonding with a CO2ꢂ, while the remaining Ag(NH3)+ is
bound to the second CO2ꢂ. This hydrogen bonding pro-
vides both charge balance as well as a second ligand for
the silver’s coordination sphere. Presumably, it is this link-
age that provides the anchor stability to the solid-state
structure that prevents NH3 loss so common to the other
anion versions [6].
where normal N–Hꢁ ꢁ ꢁO distances of 2.78–3.13 A have been
reported [6]. It is clear that the same connectivity is occur-
ring in the title complex [Ag(NH3)2Ag(NH3)TCPA]2(H2O)2
structure, where the N–Hꢁ ꢁ ꢁO distances range 2.937–
˚
3.427 A, Table 3.
While the silver atoms are stacked over each other in 2
that give the appearance of argentophilic bonding, the
˚
Ag–Ag separations, 3.143–3.366 A, are quite outside the
normal bonding range for accepted Ag–Ag bonds, 2.78–
Appendix A. Supplementary material
˚
3.0 A [13]. From a physical properties perspective, it is
noteworthy that the Xꢂ ¼ NO3ꢂ; NO2ꢂ, and SO4 com-
2ꢂ
CCDC 654180 and 654181 contain the supplementary
crystallographic data for 1 and 2. These data can be
obtained free of charge via http://www.ccdc.cam.ac.uk/
conts/retrieving.html, or from the Cambridge Crystallo-
graphic Data Centre, 12 Union Road, Cambridge CB2
1EZ, UK; fax: (+44) 1223-336-033; or e-mail: deposit@
ccdc.cam.ac.uk. Supplementary data associated with this
article can be found, in the online version, at
doi:10.1016/j.ica.2007.08.031.
plexes are all unstable as the result of NH3 loss from the
solid, beginning within just a few hours, in some cases.
The bis-[ammino-tetrachlorophthalato-silver di-ammino-
silver] complex reported here, on the other hand, is surpris-
ingly stable and the di-ammine-silver group is retained
intact.
Table 3
N–H ꢁ ꢁ ꢁ O bonding in [Ag(NH3)2Ag(NH3)TCPA]2(H2O)2, d(D–
H) = 0.890
References
D–H
d(H. . .A)
\DHA
d(D. . .A)
A
N1–H1A
N1–H1B
N1–H1C
N1–H1C
N2–H2A
N2–H2B
N2–H2C
N3–H3A
N3–H3A
N3–H3B
N3–H3C
2.320
2.353
2.243
2.434
2.143
2.440
2.225
2.515
2.642
2.111
2.284
153.82
132.73
144.01
121.51
151.75
150.01
164.77
152.62
147.66
176.27
153.52
3.144
3.028
3.009
2.997
2.957
3.242
3.092
3.331
3.427
3.000
3.106
O3
O1
O4
O2
O3
O1
O4
O4
O3
O1
O2
[1] (a) X-M. Chen, T.C.W. Mak, J. Chem. Soc., Dalton Trans. (1991)
1219;
(b) T.C.W. Mak, W-H. Yip, C.H.L. Kennard, G. Smith, E.J.
O’Reilly, Aust. J. Chem. 39 (1986) 541;
(c) B.T. Usbaliev, M. Movsumov, I.R. Amiraslanov, A.I. Akhmedov,
A.A. Musaev, Kh.S. Mamedov, Zhur. Struk. Khim. 22 (1981) 98;
(d) B.P. Tolochko, S.V. Chernov, S.G. Nikitenko, D.R. Whitcomb,
Nucl. Instr. Meth. Phys. Res. (A) 405 (1998) 428;
(e) D.R. Whitcomb, M. Rajeswaran, Polyhedron 25 (2006) 1747;
(f) L.P. Olson, D.R. Whitcomb, M. Rajeswaran, T.N. Blanton, B.J.
Stwertka, Chem. Mat. 18 (2006) 1667.

1362
D.R. Whitcomb, M. Rajeswaran / Inorganica Chimica Acta 361 (2008) 1357–1362
[2] T. Tsuda, S. Ohba, M. Takahashi, M. Ito, Acta Crystallogr., Sect. C
45 (1989) 887.
[3] (a) D.R. Whitcomb, R.D. Rogers, Inorg. Chim. Acta 256 (1997) 263;
(b) D.R. Whitcomb, R.D. Rogers, J. Chem. Cryst. 25 (1995) 137.
[4] (a) J. Fan, W.-Y. Sun, T.-A. Okamura, J. Xie, W.-X. Tang, N.
Ueyama, New J. Chem. 26 (2002) 199;
(d) U. Zachwieja, H. Jacobs, Z. Anorg. Allg. Chem. 571 (1989) 37;
(e) U. Zachwieja, H. Jacobs, Zeit. Krist. 201 (1992) 207.
[7] Nonius (1998), Nonius BV, Delft, The Netherlands.
[8] Z. Otwinowski, W. Minor, in: C.W. Carter Jr., R.M. Sweets (Eds.),
Methods in Enzymology, 276: Macromolecular Crystallography, Part
A, Academic Press, 1997, pp. 307–326.
(b) G. Smith, D.S. Sagatys, C. Dahlgren, D.E. Lynch, R.C. Bott,
K.A. Byriel, C.H.L. Kennard, Z. Kristallogr. 210 (1995) 44;
(c) G. Smith, A.N. Reddy, K.A. Byriel, C.H.L. Kennard, Polyhedron
13 (1994) 2425.
[9] SHELXTL: Structure Analysis Program, V6.10; Bruker-Nonius Analyt-
ical X-ray Systems, Madison, WI, 2000.
[10] G.W. Sheldrick, R.O. Gould, Acta Crystallogr., Sect. B 51 (1995) 423.
[11] R.H. Blessing, Acta Crystallogr., Sect. A 51 (1995) 33.
[12] (a) von M. Hedrich, H. Hartl, Acta Crystallogr., Sect. C 39 (1983) 1649;
(b) F. Charbonnier, R. Faure, H. Loiseleur, Rev. Chim. Min. 18 (1981)
245;
(c) L. Eriksson, M. Kritikos, Acta Crystallogr., Sect. C 51 (1995)
1508.
[13] F. Jaber, F. Charbonnier, M. Petit-Ramel, R. Faure, Eur. J. Solid
State Inorg. Chem. 33 (1996) 429.
[5] (a) F. Jaber, F. Charbonnier, F. Faure, Eur. J. Solid State Inorg.
Chem. 32 (1995) 25;
(b) F. Jaber, F. Charbonnier, R. Faure, J. Chem. Cryst. 24 (1994) 681;
(c) D.R. Whitcomb, R.D. Rogers, Polyhedron 16 (1997) 863;
(d) G. Smith, A.N. Reddy, K.A. Byriel, C.H.L. Kennard, J. Chem.
Soc., Dalton Trans. (1995) 3565.
[6] (a) H.M. Maurer, A. Weiss, Z. Krist. 146 (1977) 227;
(b) G.A. Bowmaker, R.K. Harris, B. Assadollahzadeh, D.C. Apper-
ley, P. Hodgkinson, P. Amornsakchai, Mag. Res. Chem. 42 (2004)
819;
[14] J.C. Slater, J. Chem. Phys. 41 (1964) 3199.
[15] X.-L. Zhao, Q.-M. Wang, T.C.W. Mak, Inorg. Chem. 42 (2003) 7872.
[16] P.J. Cowdery-Corvan, D.R. Whitcomb, in: A.S. Diamond, D.S.
Weiss (Eds.), Handbook of Imaging Materials, Marcel-Dekker, NY,
2002, p. 473.
(c) T. Yamaguchi, O. Lindqvist, Acta Chem. Scand., Phys. Inorg.
Chem. A 37 (1983) 685;