Flux Synthesis of LiAuS and NaAuS: Chicken-Wire-Like Layer Formation by Interweaving of (AuS)nn- Threads. Comparison with α-HgS and AAuS (A = K, Rb)

Article abstract of DOI:10.1021/ic980360b

From the reaction of Au with alkali metal polysulfide liquids, LiAuS and NaAuS were discovered. Orange crystals of LiAuS crystallize in the monoclinic space group C2/c, (no. 15), with a = 8.994(2) ?, b = 8.956(2) ?, c = 7.201(3) ?, β= 128.68(1)°, and Z = 8. Light-yellow planks of NaAuS crystallize in the orthorhombic space group Ccca, (no. 68), with a = 14.658(5) ?, b = 21.043(7) ?, c = 7.118(4) ?, and Z = 32. Both compounds contain infinite one-dimensional (AuS)_n^n- chains, featuring alternating sulfide anions and linear coordinated Au centers. In LiAuS, the chains are zigzag and fully extended and they pack in two mutually perpendicular sets. In NaAuS, the same chains coil in an unusual fashion so that they become interwoven to form layers reminiscent of chicken-wire . This novel coiling mode allows Au-Au contacts to form, which help to stabilize the structure. The structural relationships between LiAuS, NaAuS, Na₇Au₅S₆, AAuQ (A = K, Rb, Cs; Q = S, Se), and α-HgS are explored.

Full text of DOI:10.1021/ic980360b

Inorg. Chem. 1998, 37, 5583-5587
5583
Flux Synthesis of LiAuS and NaAuS: “Chicken-Wire-Like” Layer Formation by
Interweaving of (AuS)nn- Threads. Comparison with r-HgS and AAuS (A ) K, Rb)
Enos A. Axtell, III, Ju-Hsiou Liao, and Mercouri G. Kanatzidis*
Department of Chemistry and Center for Fundamental Materials Research, Michigan State University,
East Lansing, Michigan 48824-1322
ReceiVed April 2, 1998
From the reaction of Au with alkali metal polysulfide liquids, LiAuS and NaAuS were discovered. Orange crystals
of LiAuS crystallize in the monoclinic space group C2/c, (no. 15), with a ) 8.994(2) Å, b ) 8.956(2) Å, c )
7
.201(3) Å, â ) 128.68(1)°, and Z ) 8. Light-yellow planks of NaAuS crystallize in the orthorhombic space
group Ccca, (no. 68), with a ) 14.658(5) Å, b ) 21.043(7) Å, c ) 7.118(4) Å, and Z ) 32. Both compounds
contain infinite one-dimensional (AuS)n chains, featuring alternating sulfide anions and linear coordinated Au
n-
centers. In LiAuS, the chains are zigzag and fully extended and they pack in two mutually perpendicular sets.
In NaAuS, the same chains coil in an unusual fashion so that they become interwoven to form layers reminiscent
of “chicken-wire”. This novel coiling mode allows Au-Au contacts to form, which help to stabilize the structure.
The structural relationships between LiAuS, NaAuS, Na7Au5S6, AAuQ (A ) K, Rb, Cs; Q ) S, Se), and R-HgS
are explored.
Introduction
Experimental Section
Reactions of gold with polychalcogenide melts can go quickly
to completion at temperatures as low as 190 °C. This reactivity
Reagents. Elemental sulfur was purchased from Spectrum Chemical
Manufacturing Corporation. Sodium and lithium were obtained from
Aldrich. Au metal (99.99%) was acquired from Liberty Coins, Lansing,
MI. Chemicals were measured and loaded in Pyrex tubes under a dry
nitrogen atmosphere in a Vacuum Atmospheres Dri-Lab glovebox.
Lithium metal was manipulated under an argon atmosphere to avoid
1
was pointed out by Bertholet in the early 1800’s when he
reported that gold dissolved in alkali metal polysulfide melts
but not in molten sulfur.2 This high reactivity makes the
A/Au/Q systems (A ) alkali metal; Q ) S, Se, Te) interesting
for study from a chemical standpoint because many ternary
phases are possible. The strong affinity of gold for chalcogen
atoms is evident in the number of ternary compounds that have
3
the formation of Li N.
Synthesis. a. Finely Divided Au Metal. A gold coin (99.99%,
31.1 g) was dissolved in 400 mL of aqua regia (300 mL of concentrated
3
4
HCl and 100 mL of concentrated HNO ). The solution was boiled in
been reported, NaAuSe, KAuQ (Q ) S, Se), AAuQ (A ) K,
3
5
6a
6b
an acid-resistant fume hood to a volume of approximately 100 mL.
The solution was neutralized with ammonium hydroxide, and the gold
was reduced with excess hydrazine hydrochloride dissolved in 100 mL
of distilled water. The resulting black suspension was heated gently,
with stirring, for 1 h to allow particle aggregation. After the suspension
was filtered and washed with copious amounts of distilled water and
acetone, the resulting gold powder was heated in air for 2 h at 300 °C
to drive off any remaining impurities, yielding 30.9 g of Au powder.
Note: heating too long or at too high a temperature results in impractical
grain sizes.
Rb, Cs), AAuTe (A ) Na, K, Rb, Cs), Na3AuS2, Na7Au5S6,
7
7
8
9
AAu3S2 (A ) Cs, Rb), CsAu3Se2, Cs4Au6S5, K4Au6S5, K7-
9
13
Au5S7, and AAuSe2 (A ) Na, K), containing monochalco-
10,11
10,11
genide ligands as well as K3AuSe13,
Na3AuSe8,
K5-
AuSe12, KAuQ5 (Q ) S, Se), and CsAuSe3,13 which feature
1
2
12
long-chain polychalcogenides. Here, we describe LiAuS and
n-
NaAuS, both of which feature infinite (AuS)n chains in
remarkable conformations and arrangements.
(
1) Kanatzidis, M. G.; Sutorik, A. C. Prog. Inorg. Chem. 1995, 43, 151-
64.
2 2
b. Li S and Na S. Lithium sulfide and sodium sulfide were
2
(
2) Bertholet, C. L. Essai de Statique Chimique, 2nd Partie; Paris, 1803;
p 437.
produced in liquid ammonia. In a nitrogen-filled glovebox, the
stoichiometric amounts of alkali metal chunks and elemental sulfur
powder necessary to produce 20 g of starting material were loaded
into a 250 mL round-bottom flask. A Teflon stir bar was added, and
each flask was closed to air with a glass adapter and valve. The
apparatus was removed to a Schlenk line, where approximately 150
mL of liquid ammonia was condensed under nitrogen, with stirring,
into the dry-ice/acetone-cooled round-bottom flask. After the flask was
allowed to warm to room temperature, the apparatus was put under
vacuum for several hours, followed by heating with a hot air gun to
drive off any remaining ammonia. The apparatus was returned to the
glovebox, and the product was ground to a fine powder before use.
The resulting powders were pale yellow in color.
(
(
3) Klepp, K. O. J. Alloys Compd. 1996, 234, 199-202.
4) Klepp, K. O.; Bronger, W. J. Less-Common Met. 1987, 132, 1173-
9.
(
5) (a) Bronger, W.; Kathage, H. U. J. Alloys Compd. 1992, 184, 87. (b)
Bronger, W.; Kathage, H. U. J. Less-Common Met. 1990, 160, 181.
6) (a) Klepp, K. O.; Bronger, W. J. Less-Common Met. 1987, 127, 65-
(
7
2
1. (b) Klepp, K. O.; Brunnbauer, G. J. Alloys Compd. 1992, 183,
52-62.
(
(
(
7) Klepp, K. O.; Weithaler, C. J. Alloys Compd. 1996, 243, 1-5.
8) Klepp, K. O.; Weithaler, C. J. Alloys Compd. 1996, 243, 12-18.
9) Klepp, K. O.; Bronger, W. J. Less-Common Met. 1988, 137, 13-20.
(
10) Park, Y.; Kanatzidis, M. G. Angew. Chem., Int. Ed. Engl. 1990, 29,
914-5.
(
(
11) Kanatzidis, M. G. Chem. Mater. 1990, 2, 353-363.
12) Klepp, K. O.; Weithaler, C. Abstracts of the European Meeting on
Solid State Chemistry, Montpellier, VT, Sept 1995; A95.
13) Park, Y. Ph.D. Dissertation, Michigan State University, East Lansing,
MI, 1991.
c. LiAuS. Orange crystals of LiAuS were obtained by the reaction
of 1-4 equiv of Li S, 1 equiv of Au metal, and 8 equiv of elemental
2
S. This charge was sealed inside an evacuated Pyrex tube. The tube
(
was placed inside a computer-controlled furnace and heated at 500 °C
1
0.1021/ic980360b CCC: $15.00 © 1998 American Chemical Society
Published on Web 09/25/1998

5584 Inorganic Chemistry, Vol. 37, No. 21, 1998
Axtell et al.
Figure 1. (A) A view of the structure of LiAuS along [1 0 0] (Au, black circles; S, open circles; Li, gray small circles) (50% probability). (B) The
structure of LiAuS along [0 0 1]. The Li atoms are the small black circles.
Table 1. Summary of Crystallographic Data for LiAuS and
Table 3. Fractional Atomic Coordinates and Beqa Values for
NaAuS
NaAuS, with Estimated Standard Deviations in Parentheses
formula
fw
a
b
c
NaAuS
252.02 g/mol
LiAuS
235.97 g/mol
Wyckoff
symbol
atom
x
y
z
B
eq
14.658(5) Å
21.043(7) Å
7.118(4) Å
90°
8.994(2) Å
8.956(2) Å
7.201(3) Å
128.68(1)°
452.8(5) Å
Au1
Au2
Au3
S1
16i
8g
8d
16i
16i
8e
0.1180(2) 0.3733(2)
0.2196(5) 2.1(1)
0.465(1)
0.0
0.491(3)
-0.040(3)
0.75
0.0
0.0
0.25
2.7(4)
2.1(3)
2(1)
2(1)
3(3)
2(2)
2(2)
0.5
â
V
0.128(6)
0.129(5)
0.249(4)
1.0
0.313(1)
0.440(1)
0.25
0.138(2)
0.066(2)
3
3
2195(3) Å
S2
space group Ccca (no. 68)
Z
C2/c (no. 15)
Na1
Na2
Na3
32
6.10 g/cm
539.68 cm
8
8f
16i
0.75
0.092(4)
3
3
d
calc
6.92 g/cm
652.2 cm
0.691(3)
-
1
-1
µ(Mo KR)
a
B values for anisotropically refined atoms are given in the form of
the isotropic equivalent displacement parameters defined as Beq ) (4/
radiation
Mo KR (λ ) 0.710 69 Å) Mo KR (λ ) 0.710 69 Å)
5.6%/8.3%
a
R/R
w
2.6%/3.2%
2
2
2
3
)[a B(1,1) + b B(2,2) + c B(3,3) + ab(cos γ)B(1,2) + ac(cos â)B(1,3)
a
2
|2}1/2, w
R ) ∑(|F
o
| - |F |)/∑|F
c
o
|, R
w
) {∑w(|F
o
| - |F
c
|) /∑w|F
o
+ bc(cos R)B(2,3)].
2
)
1/σ (F).
a
Table 2. Fractional Atomic Coordinates and Beq Values for
LiAuS, with Estimated Standard Deviations in Parentheses
Wyckoff
atom
symbol
x
y
z
B
eq
Au1
Au2
S
4a
4d
8f
8f
0.0
0.25
0.0
0.25
0.0
0.5
1.32(3)
1.31(3)
0.2864(6) 0.1252(5) 0.2500(6) 1.2(1)
0.149(5) 0.377(1) 0.043(5) 2.3(9)
Li
a
B values for anisotropically refined atoms are given in the form of
the isotropic equivalent displacement parameters defined as Beq ) (4/
2
2
2
3
+
)[a B(1,1) + b B(2,2) + c B(3,3) + ab(cos γ)B(1,2) + ac(cos â)B(1,3)
bc(cos R)B(2,3)].
for 4 days and then cooled at 4 °C/h to 100 °C and at 20 °C/h to room
temperature. The product was isolated with methanol under a nitrogen
atmosphere. The compound is stable in H O and common organic
2
solvents such as alcohols, acetonitrile, and acetone, but it slowly
decomposes in air over several days. Analysis on a number of these
crystals by SEM/EDS indicated the present of Au and S. (Li is too
light to be detected through the Be window of the detector.) For the
purposes of phase identification, a measured powder pattern was
Figure 2. A projection view of the structure of LiAuS along [-1 1
-
2]. For clarity, Li atoms have been deleted (Au, black circles; S,
open circles).
14
inside an evacuated Pyrex tube, which was then placed inside a
computer-controlled furnace. The tube was heated at 550 °C for 3
days and then cooled at 5 °C/h to 200 °C and at 20 °C/h to room
temperature. The product was isolated with methanol under a nitrogen
compared to one calculated from the appropriate structural parameters.
d. NaAuS. Light-yellow rods of NaAuS were obtained from the
reaction of 0.195 g (2.5 mmol) of Na
2
S, 0.098 g (0.5 mmol) of Au
metal, and 0.128 g (4.0 mmol) of elemental S. The charge was sealed
2
atmosphere. The compound is insoluble in H O and common organic
solvents and is stable to air exposure for over a week. For the purposes
of phase identification, a measured powder pattern was compared to
one calculated14 from the appropriate structural parameters.
(
14) Smith, D. K.; Nichols, M. C.; Zolensky, M. E. POWD10: A FORTRAN
IV Program for Calculating X-ray Powder Diffraction Patterns,
version 10; Pennsylvania State University: State College, PA, 1983.

Flux Synthesis of LiAuS and NaAuS
Inorganic Chemistry, Vol. 37, No. 21, 1998 5585
Figure 3. Three views of the coiling of the (AuS) n-
chains in NaAuS (Au, black circles; S, open circles).
n
Table 5. Selected Bond Angles for LiAuS and NaAuS, with
Standard Deviations in Parenthesesa
atom-atom-atom angle (deg) atom-atom-atom angle (deg)
LiAuS
S-Au1-S
S-Au2-S
Au1-S-Au2
S-Li-S
180
180
S-Li-S
S-Li-S
S-Li-S
S-Li-S
112(1)
114(1)
102(1)
98.9(9)
102.1(2)
125(1)
102(1)
S-Li-S
NaAuS
S1-Au1-S2
S1-Au2-S1
S2-Au3-S2
Au1-S1-Au2
Au1-S2-Au3
S1-Na1-S1
S1-Na1-S1
S1-Na1-S1
S1-Na1-S1
S1-Na1-S1
171.5(8)
171(1)
180
S1-Na2-S2
S1-Na2-S2
S2-Na2-S2
S1-Na3-S2
S1-Na3-S2
S1-Na3-S2
S2-Na3-S2
S2-Na3-S2
S2-Na3-S2
96.3(7)
107(6)
112(2)
105(2)
130(1)
100(1)
99(2)
101(2)
100(2)
125(1)
103(2)
104(3)
100(3)
137(2)
Figure 4. A projection view of the structure of KAuS along [0 0 1]
(Au, black circles; S, open circles; K, gray circles).
128(2)
98(2)
Table 4. Selected Bond Distances for LiAuS and NaAuS, with
Standard Deviations in Parenthesesa
a
The estimated standard deviations in the mean bond angles are
2
1/2
atom-atom
distance (Å)
atom-atom
distance (Å)
calculated by the equation σl ) {∑ (l - l) /n(n - 1)} , where l is
the angle of the nth bond, l is the mean angle, and n is the number of
angles.
n
n
n
LiAuS
Au1-Au2
Au1-S
Au2-S
Li-S
3.1732(6)
2.310(4)
2.309(4)
2.56(3)
Li-S
Li-S
Li-S
2.51(3)
2.54(3)
2.53(3)
NaAuS
Au2-Au2
Au1-S1
Au1-S2
Au2-S1
Au3-S2
Na1-S1
Na1-S1
3.06(1)
2.32(3)
2.32(2)
2.30(7)
2.30(6)
2.87(7)
2.82(7)
Na2-S1
Na2-S2
Na3-S1
Na3-S2
Na3-S2
Na3-S2
2.82(6)
2.92(5)
2.81(5)
2.78(4)
2.96(4)
2.80(7)
a
The estimated standard deviations in the mean bond length are
2
1/2
calculated by the equation σl ) {∑
the length of the nth bond, l is the mean length, and n is the number
n
(l
n
n
- l) /n(n - 1)} , where l is
of bonds.
Crystallographic Studies. a. Single-Crystal X-ray Diffraction.
Single-crystal X-ray diffraction data for LiAuS and NaAuS were
collected on a computer-controlled Rigaku AFC6S four-circle autod-
iffractometer (Mo KR radiation, graphite monochromated, at 23 °C).
The cell parameters were determined by least-squares refinement of
n-
Figure 5. A view of the interweaving pattern of the (AuS)
in NaAuS (Au, black circles; S, open circles).
n
chains
1
6-25 computer-centered reflections. The intensity data were collected
isotropically refined structure. All atoms were eventually refined
anisotropically. All calculations were performed on a VAX Station
with the ω-2θ scan technique at the speed of 4.0 deg/min. None of
the crystals showed significant decay as judged by three check
reflections measured every 150 reflections throughout their respective
data sets. The space groups were determined from the systematic
absences and intensity statistics. The structures were solved by the
direct methods routine of SHELXS-86 and refined by the full-matrix
least-squares techniques of the TEXSAN package of crystallographic
programs. An empirical absorption correction based on ψ-scans was
3100/76 computer. The complete parameters and details of the structure
(
15) Sheldrick, G. M. In Crystallographic Computing 3; Sheldrick, G. M.,
Kruger, C., Doddard, R., Eds.; Oxford University Press: Oxford,
England, 1985; pp 175-89.
1
5
(16) TEXSAN: Single-Crystal Structure Analysis Software, version 5.0;
Molecular Structure Corp.: The Woodlands, TX, 1989.
16
1
7
applied to each data set, followed by a DIFABS correction to the
(17) Walker, N.; Stuart, D. Acta Crystallogr. 1983, 39A, 158.

5586 Inorganic Chemistry, Vol. 37, No. 21, 1998
Axtell et al.
Figure 6. (A) A projection view of the structure of NaAuS along [0 0 1]. (B) A view of the structure of NaAuS along [0 1 0].
compounds.18 In this compound, the chains have a simple
zigzag pattern and are stretched out in a linear manner. With
all the freedom about the linearly coordinated gold atoms, more
complicated chain geometries are possible; see below.
solution and refinement for the compounds are given in Table 1. The
higher R values and thermal parameters in NaAuS are due to the poor
crystal quality of the sample. The coordinates of all atoms, isotropic
equivalent temperature factors, site multiplicities, and their standard
deviations are given in Tables 2 and 3.
b. NaAuS. The structure of NaAuS also consists of
b. Powder X-ray Diffraction. The compounds were examined
by X-ray powder diffraction to check for phase purity and for
identification. The products obtained by the above methods of
preparation were pure as judged by optical examination as well as X-ray
powder diffraction. Powder patterns obtained on a Philips XRG-3000
powder diffractometer and a Rigaku rotating anode (Cu KR) X-ray
powder diffractometer, Rigaku-Denki/Rw400F2 (RotaFlex), provided
accurate dhkl spacings.
n-
infinitely one-dimensional (AuS)n chains; see Figure 3a. Such
chains are not unusual in and of themselves; they exist in the
4
isoelectronic compounds AAuQ (A ) K, Rb; Q ) S, Se) and
19
R-HgS. An end-on view of one of the chains in R-HgS would
n-
reveal a triangular cross section. Interestingly, no (AuS)n
chain has yet been found to adopt a HgS-type of conformation.
In NaAuS, the conformation and packing of the isoelectronic
chains are much more elaborate than in any of the other
analogues. Meanwhile, KAuS forms straight chains reminiscent
of those seen above in LiAuS. In KAuS, the chains do not
form perpendicular sets but line up in a parallel fashion; see
Figure 4. In NaAuS, the coiling and packing is unique. In an
elaborate corkscrew manner, the chains trace figure eights as
they propagate, circling first in a clockwise manner and then in
a counterclockwise manner; see Figure 3B. Of course, the
projection view of one of these chains would appear to be a
figure eight; see Figure 3C. In contrast, the chains in R-HgS
coil into simple spirals with a projection down their axis being
a simple equilateral triangle. In these chains, the Au-S bond
lengths are normal, ranging from 2.30(7) to 2.32(2) Å. The
S-Au-S angles, at 171.5(8)°, 171(1)°, and 180° for Au1, Au2,
and Au3, respectively, are normal (Tables 4 and 5). Each
sodium atom is coordinated by four sulfur atoms in a tetrahedral
fashion. The Na-S distances vary from 2.80(7) to 2.96(4) Å.
Results and Discussion
Structure Description. a. LiAuS. The structure of LiAuS
n-
consists of two nearly perpendicular sets of (AuS)n zigzag
chains, as seen in the projection view along [1 0 0] in Figure
1
A. In this figure, Au atoms are black, sulfur atoms are white,
and Li atoms are gray. The Au-S distances are normal, with
Au1-S at 2.310(4) Å and Au2-S at 2.309(4) Å. The S-Au-S
angle is constrained by symmetry to be 180°, a normal bond
angle about Au.
Another view nearly along the [0 0 1] direction also reveals
the two parallel sets of chains. In addition, channels are visible
along this direction. Interestingly, the lithium atoms are situated
near the sulfur columns and not in the middle of the channel;
see Figure 1B. The immediate environment of the Li ions is
tetrahedral, with Li-S distances varying from 2.51(3) to 2.56-
n-
In NaAuS, (AuS)n chains pack together by interweaving
with each other. Each chain weaves through the two chains on
either side of it, resulting in a “chicken-wire-like” mesh; see
Figure 5. There are Au2-Au2 contacts between chains, at a
distance of 3.06(1) Å. Other Au-Au distances are longer,
ranging from 3.486(7) to 3.752(4) Å. The meshes form layers
which include Na atoms; see Figure 6. There are also interlayer
(3) Å.
To better see that the chains are in fact separate from each
other, a projection view down the [-1 1 -2] direction is useful.
One set of chains is in the plane of Figure 2, while one set is
directed vertically out of the page. Within the set of chains in
the plane of the figure, the Au-Au distance is half of the b-axis
length, or 4.478 Å (i.e., the distance between two adjacent gold
+
Na cations, as seen in Figure 6 as well.
n-
atoms in a given (AuS)n chain). The shortest Au-Au distance
(
(
18) Axtell, E. A., III; Kanatzidis, M. G. Chem.sEur. J., in press.
19) Auvray, P.; Genet, F. Bull. Soc. Fr. Mineral. Cristallogr. 1973, 96,
218-219.
occurs between chains, at 3.1732(6) Å. Distances of this order
have been seen before in the A2Au2Cd2S4 (A ) Rb, Cs)

Flux Synthesis of LiAuS and NaAuS
Inorganic Chemistry, Vol. 37, No. 21, 1998 5587
6
NaAuS and Na7Au5S6 both contain this unusual “chicken-
covalency in A-S (or A-O) bonds increases from the bottom
to the top of the group. The surprising moisture stability of
LiAuS also suggests that this material has characteristics that
are closer to those of a three-dimensional material than to those
of a low-dimensional material.
wire-like” layer. In the latter compound, the meshes are further
separated by a layer of linear discrete AuS2 anions as well as
the Na cations necessary to balance the charge. These AuS2
dumbbell anions are observed by themselves in the compound
Na3AuS2. Upon reflection then, it is easy to see how the
compounds are related stoichiometrically.
3-
+
3-
5
The variability in the packing of the chains in the AAuS series
(A ) alkali metal) suggests that mixed cation reactions may be
interesting and may yield other coiling motifs of the highly
n-
Na Au S (NaAuS) + Na AuS ) Na Au S
5 6
flexible (AuS)n species.
4
4
4
3
2
7
Acknowledgment. Financial support from the National
Science Foundation DMR-9527347 is gratefully acknowledged.
M.G.K. is an A. P. Sloan Foundation and a Camille and Henry
Dreyfus Teacher Scholar 1993-98. This work made use of the
SEM facilities of the Center for Electron Optics at Michigan
State University.
The band gap of LiAuS was determined to be 2.1 eV, while
the melting point and the crystallization point were determined
to be 573 and 553 °C, respectively, by techniques standard in
2
0
this laboratory. By comparison, the band gap of NaAuS is
2
.7 eV, considerably larger than that of the Li analogue; this
-
suggests that the Li ions interact with the [AuS] substructure
much more strongly than the Na ions. This is consistent with
the expected trend in alkali metal atoms where the degree of
Supporting Information Available: Tables listing crystallographic
data, atomic positional coordinates of all atoms, and bond lengths and
angles for LiAuS and NaAuS (12 pages). Ordering information is given
on any current masthead page.
(
20) McCarthy, T. J.; Ngeyi, S.-P.; Liao, J.-H.; DeGroot, D. C.; Schindler,
J.; Kannewurf, C. R.; Kanatzidis, M. G. Chem. Mater. 1993, 5, 331-
340.
IC980360B