inorganics
Article
The A-Type Ln4N2S3 Series: New Nitride Sulfides of
the Light Lanthanoids (Ln = Ce–Nd)
Falk Lissner and Thomas Schleid *
Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany;
[email protected]
* Correspondence: [email protected]; Tel.: +49-711-685-64240
Academic Editor: Duncan H. Gregory
Received: 11 November 2016; Accepted: 14 December 2016; Published: 23 December 2016
Abstract: The reaction of lanthanoid metal powders (Ln) with sulfur and cesium azide (CsN3 ) as a
nitrogen source in the presence of lanthanoid tribromides (LnBr3 ) yields lanthanoid nitride sulfides
with the composition Ln4 N2 S3 (Ln = Ce–Nd) when appropriate molar ratios of the starting material are
used. Additional cesium bromide (CsBr) as a flux secures quantitative conversion (7 days) at 900 ◦ C
in evacuated silica tubes as well as the formation of black single crystals. All compounds crystallize
isotypically with the orthorhombic crystal structure of La4 N2 S3 (Pnnm, Z = 2) and their structures
were determined from single-crystal X-ray diffraction data (Ce4 N2 S3 : a = 644.31(4), b = 1554.13(9),
c = 404.20(3) pm; Pr4 N2 S3 : a = 641.23(4), b = 1542.37(9), c = 400.18(3) pm; Nd4 N2 S3 : a = 635.19(4),
b = 1536.98(9), c = 397.85(3) pm). Compared to La4 N2 S3 the a-axes do not fulfill the expectation
of the lanthanide contraction. The main feature of the crystal structure comprises N3− -centered
(Ln3+ )4 tetrahedra arranging as pairs [N2 Ln6 ]12+ of edge-shared [NLn4 ]9+ units, which are further
1 {([NLn
6+
connected via four vertices to form double chains ∞
4/2 ]2 ) }. Bundled along [001] like a
hexagonal rod packing, they are held together by two crystallographically different S2− anions.
Two compounds of a second modification (B-type La4 N2 S3 and Pr4 N2 S3 ) will also be presented and
discussed for comparison.
Keywords: lanthanoid nitride sulfides; dimorphic crystal structures
1. Introduction
The crystal structures of all ternary lanthanide(III) nitride chalcogenides known so far
(Ln3 NCh3 , Ln4 N2 Ch3 , Ln5 NCh6 , Ln23 N5 Ch27 , and Ln13 N5 Ch12 ) and their halide derivatives (Ln3 N2 ChX,
Ln4 NCh3 X3 , Ln5 N2 Ch4 X, Ln5 N3 Ch2 X2 , and Ln6 N3 Ch4 X; Ln = La–Nd, Sm, Gd–Ho; Ch = S, Se, Te; X = Cl,
Br) are dominated by N3− anions in a tetrahedral coordination of Ln3+ cations [1–3]. A very interesting
structural behavior is exhibited by the nitride chalcogenides with the composition Ln4 N2 Ch3 , which
occur in seven different crystal structure types. Depending upon the size of both the lanthanide
cation (Ln3+ ) and the chalcogenide anion (Ch2− ), some of them differ fundamentally in the linkage of
the structure-governing N3− -centered (Ln3+ )4 tetrahedra. The representatives of the Sm4 N2 S3 -type
structure [4] crystallize in the monoclinic space group C2/m with Z = 4 and consist of [NLn4 ]9+
1 {[NLn ]3+ }. In contrast, the linkage
tetrahedra, which share cis-oriented edges to form linear strands ∞
2
via trans-oriented edges of [NLn4 ]9+ tetrahedra builds up undulated chains in the orthorhombic
Ce4 N2 Te3 -type structure [5] (Ln = La–Nd; Pnma, Z = 4), the orthorhombic Tb4 N2 Te3 -type structure [6]
(Ln = Gd, Tb; Pnna, Z = 4), and the monoclinic Dy4 N2 Te3 -type structure [6] (P21 /c, Z = 4). As the main
structural feature of the orthorhombic A-La4 N2 S3 -type structure [7] (Pnnm, Z = 2), N3− -centered (Ln3+ )4
tetrahedra, which first arrange as pairs [N2 Ln6 ]12+ of two edge-shared [NLn4 ]9+ units, occur. These are
1 {([NLn ] )6+ }. For the first time,
further connected via their four free vertices to form double chains ∞
2 2
9+
an arrangement of interconnected [NLn4 ] tetrahedra fused to layers is observed in the monoclinic
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an arrangement of interconnected [NLn4]9+ tetrahedra fused to layers is observed in the monoclinic
Nd4N2Se3-type structure [8–11] (Ln = La–Nd; C2/c, Z = 4). In these compounds the [NLn4]9+ units are
Nd4 N
[8–11]
(Ln = La–Nd;
Z = 4). In these compounds the [NLn4 ]9+ units are
2 Se3 -type structure
first
edge-linked
to congonial
bitetrahedra
[NC2/c,
2Ln6]12+ again, and they then become cross-connected
to
12+
first
edge-linked
to congonial bitetrahedra [N2 Ln6 ]
again, and they then become cross-connected
2
3+
∞ {[NLn2] } layers via their remaining four free vertices. Finally, a second layered arrangement is
2 {[NLn ]3+ } layers via their remaining four free vertices. Finally, a second layered arrangement
to ∞
2
found
in the
monoclinic B-Pr4N2S3-type structure [9] (Ln = La, Pr; C2/c, Z = 8). In this case, the [NLn4]9+
is found in the monoclinic B-Pr4 N2 S3 -type structure [9]
(Ln = La, Pr; C2/c, Z = 8). In this case,
tetrahedra 9+
are first edge-linked to bitetrahedra [N2Ln6]12+ just like in 12+
A-type La4N2S3 and Nd4N2Se3,
the [NLn4 ] tetrahedra are first edge-linked to bitetrahedra
[N2 Ln6 ]
just like in A-type La4 N2 S3
but then connected via two vertices to quadruples [N4Ln10]18+, which
eventually
build up layers
and
Nd43+
N2 Se3 , but then connected via two vertices to quadruples [N4 Ln10 ]18+ , which eventually
2
four3+remaining free corners. In addition, there are only two compounds
∞ {[NLn2] } via their
2 {[NLn
build
up layers ∞
2 ] } via their four remaining free corners. In addition, there are only two
crystallizing dimorphously so far. La4N2S3 [7,12] is found in the A-La4N2S3- and in the B-Pr4N2S3-type
compounds crystallizing dimorphously so far. La4 N2 S3 [7,12] is found in the A-La4 N2 S3 - and in
structures, while Ce4N2Se3 is observed either with the Nd4N2Se3- or with the Ce4N2Te3-type
the B-Pr4 N2 S3 -type structures, while Ce4 N2 Se3 is observed either with the Nd4 N2 Se3 - or with the
arrangement.
Ce4 N2 Te3 -type arrangement.
2.
2. Results
Results and
and Discussion
Discussion
The
of the
the short
short Ln
Ln44N
The members
members of
N22SS33 series
series (Ln
(Ln ==Ce–Nd)
Ce–Nd)crystallize
crystallize orthorhombically
orthorhombically in
in the
the space
space
group
Pnnm with
withtwo
twoformula
formulaunits
units(Z(Z
= 2)
unit
(Tables
are therefore
isotypical
group Pnnm
= 2)
perper
unit
cellcell
(Tables
1–3)1–3)
and and
are therefore
isotypical
with
3+
3+
with
the
A-type
structure
of
La
4
N
2
S
3
[7].
Each
of
the
two
crystallographically
independent
Lnis
the A-type structure of La4 N2 S3 [7]. Each of the two crystallographically independent Ln cations
3+ even four plus
− anions.
3+ another
cations
is firstly surrounded
two N3−For
anions.
(Ln1)3+ four,
another
foreven
(Ln2)four
firstly surrounded
by two N3by
(Ln1)For
for four,
(Ln2)3+
plus one S2−
2−
one
S appear
anions appear
their coordination
spheres,
thus resulting
in overall
coordination
numbers
anions
in theirin
coordination
spheres,
thus resulting
in overall
coordination
numbers
(C.N.)
3+ having the site symmetry (.m) can be described as
3+
(C.N.)
of
6
and
6+1.
The
polyhedron
around
(Ln1)
of 6 and 6+1. The polyhedron around (Ln1) having the site symmetry (..m) can be described as a
atrigonal
trigonal
prism
(Figure
left),
which
both
a prism
edge
(N···N′)
well
center
(Ln1)
reside
prism
(Figure
1, 1,
left),
in in
which
both
a prism
edge
(N···
N0 ) as as
well
as as
thethe
center
(Ln1)
reside
on
3+
3+
on
a
mirror
plane.
(Ln2)
,
likewise
with
the
site
symmetry
(.m),
shows
a
trigonal
prism
or
a mirror plane. (Ln2) , likewise with the site symmetry (..m), shows a trigonal prism or octahedron
octahedron
as
a
coordination
polyhedron,
which
again
proves
to
be
very
distorted,
since
it
exhibits,
as a coordination polyhedron, which again proves to be very distorted, since it exhibits, in addition,
3+–S2−) for Ln
3+ –S2− )d(Ln
in
addition,
another
(S2″)
as a cap
(Figure
1, distances
right). Thed(Ln
distances
another
extra
sulfur extra
ligandsulfur
(S2”)ligand
as a cap
(Figure
1, right).
The
for Ln
= Ce–Nd
=start
Ce–Nd
start
at
283
pm
and
increase
continuously
up
to
a
value
of
308
pm.
For
A-type
La
4N2S3 (a =
at 283 pm and increase continuously up to a value of 308 pm. For A-type La4 N2 S3 (a = 641.98(4),
641.98(4),
b = 1581.42(9),
c = 409.87(3)
pm)following
[7], the following
ligand provides
abrupt of
increase
of
b = 1581.42(9),
c = 409.87(3)
pm) [7], the
ligand provides
an abruptanincrease
distance
distance (d(La2–S2″)
= but
341 shows
pm), but
shows=an
ECoN
= 0.26
(effective coordination
[13]);
(d(La2–S2”)
= 341 pm),
an ECoN
0.26
(effective
coordination
number [13]);number
nevertheless,
3+
3+
nevertheless,
it
is
a
sound
contribution
to
be
considered
for
the
whole
coordination
sphere
of
(La2)
it is a sound contribution to be considered for the whole coordination sphere of (La2) . In spite of.
In
of thecontraction
lanthanide
as anticipated,
the
compounds Ln4N2S3 (Ln = Ce–Nd)
the spite
lanthanide
as contraction
anticipated, the
compounds Ln
4 N2 S3 (Ln = Ce–Nd) investigated in this
investigated
in
this
work
show
a
remarkable
devolution
of
this
mentioned distance
d(Ln2–S2″).
First
work show a remarkable devolution of this mentioned distance d(Ln2–S2”).
First an increase
happens
an
increase
happens
from
341
to
351
pm
during
the
transition
from
the
lanthanum
to
the
cerium
from 341 to 351 pm during the transition from the lanthanum to the cerium compound, accompanied
compound,
accompanied
by of
a decreasing
ECoN
value of compounds
0.13. With the
subsequent
compounds
by a decreasing
ECoN value
0.13. With the
subsequent
Pr4 N
2 S3 and Nd4 N2 S3 , this
Pr
4N2S3 and Nd4N2S3, this distance stagnates and finally decreases again to values of 350 and 343 pm
distance stagnates and finally decreases again to values of 350 and 343 pm (Table 4 and Figure 2,
(Table
and Figure
yellow
graph),
can at but
most
speak
a 6+1-fold
butcoordination
never of a real
yellow 4graph),
so one2,can
at most
speakso
ofone
a 6+1-fold
never
of aofreal
seven-fold
for
3+
3+
seven-fold
coordination
for
(Ln2)
(Ln
=
Ce–Nd).
This
behavior
is
also
repeated
in
the
lattice
(Ln2) (Ln = Ce–Nd). This behavior is also repeated in the lattice constants (Table 1 and Figure 2),
constants
(Table
1 and
Figure
2), where
in theofextreme
case
an the
unusual
increase
of the
a-axis
from the
where
in the
extreme
case
an unusual
increase
the a-axis
from
lanthanum
to the
cerium
compound
lanthanum
to the The
cerium
compound
observed. The
molar volumes
m monotonically decrease
can be observed.
molar
volumescan
Vm be
monotonically
decrease
with theVincreasing
atomic number
with
the
increasing
atomic
number
of
Ln,
which
finally
reflects
the
lanthanide
contraction
again.
of Ln, which finally reflects the lanthanide contraction again.
3+ and (Ln2)3+
3+ in the A-type crystal structure
Figure 1. Coordination polyhedra around (Ln1)
(Ln1)3+ and
(Ln2) in
the A-type crystal structure of the
Ln
N
S
series
(Ln
=
Ce–Nd).
Ln44N22S33series (Ln = Ce–Nd).
Inorganics 2017, 5, 2
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Table 1. Crystallographic data for the three members of the Ln4 N2 S3 series (Ln = Ce–Nd).
Compound
Ce4 N2 S3
Pr4 N2 S3
Nd4 N2 S3
Crystal system
Space group
a/pm
b/pm
c/pm
Z
Vm /cm3 ·mol−1
Dx /g·cm−3
Device
Radiation
±h, ±k, ±l
2θ max /◦
F(000)
Absorption correction
µ/mm−1
Extinction (g)
Measured reflections
Independent reflections
Refl. with |Fo | ≥ 4σ(Fo )
Rint , Rσ
Structure solution and refinement
Scattering factors
R1 , R1 with |Fo | ≥ 4α(Fo )
wR2 , GooF
Resid. electron density ρmax ,
ρmin /10−6 pm−3
CSD numbers 1
orthorhombic
Pnnm (no. 58)
644.31(4)
641.23(4)
635.19(4)
1554.13(9)
1542.37(9)
1536.98(9)
404.20(3)
400.18(3)
397.85(3)
2
121.87(2)
119.17(2)
116.95(2)
5.618
5.772
5.995
Nonius Kappa-CCD (Bruker AXS)
Mo-Kα (λ = 71.07 pm)
8, 20, 5
8, 20, 5
8, 20, 5
56.54
56.60
56.39
588
596
604
numerically (X-SHAPE [14])
22.75
24.88
27.00
0.0053
0.0008
0.0007
9071
7386
6968
575
552
546
538
457
494
0.048, 0.016
0.058, 0.022
0.067, 0.025
SHELX-97 [15]
International Tables, Vol. C [16]
0.021, 0.018
0.041, 0.029
0.035, 0.028
0.036, 1.174
0.064, 1.100
0.049, 1.166
1.02, −1.03
1.56, −1.32
1.11, −1.11
431115
431117
431116
1
Details of the structure refinements are available at the Fachinformationszentrum Karlsruhe (FIZ),
76344 Eggenstein-Leopoldshafen, Germany ([email protected]), on quoting the CSD numbers.
Table 2. Fractional atomic coordinates for the three members of the Ln4 N2 S3 series (Ln = Ce–Nd).
Atom
Ln1
Ln2
N
S1
S2
Site 1
4g
4g
4g
2a
4g
Ce4 N2 S3
Pr4 N2 S3
Nd4 N2 S3
x/a
y/b
x/a
y/b
x/a
y/b
0.22375(5)
0.26571(5)
0.1313(7)
0
0.2680(2)
0.56460(2)
0.84323(2)
0.4154(3)
0
0.20004(8)
0.22392(9)
0.26709(9)
0.1312(13)
0
0.2683(5)
0.56451(3)
0.84333(3)
0.4164(6)
0
0.20011(16)
0.22374(7)
0.26598(8)
0.1312(12)
0
0.2636(4)
0.56437(3)
0.84315(3)
0.4154(5)
0
0.19985(14)
1
z/c = 0 for all positions.
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Table 3. Anisotropic displacement parameters (Uij 1/pm2) for the three members of the Ln4N2S3 series
(Ln = Ce–Nd).
Table 3. Anisotropic displacement parameters (Uij 1 /pm2 ) for the three members of the Ln4 N2 S3 series
Compound Atom
U11
U22
U33
U23
U13
U12
(Ln = Ce–Nd).
Ce1
71(2)
51(2)
50(2)
0
0
−4(1)
Atom
Ce2
U11103(2)
U2245(2)
U33
46(2)
U23 0
U13 0
U12 −6(1)
Ce4N2S3 Ce1 N
Ce2 S1
Ce4 N2 S3
N
S2
S1
S2 Pr1
Pr1 Pr2
Pr4N2S3 Pr2 N
Pr4 N2 S3
N S1
S1
S2
S2
Nd1
Nd1
Nd2Nd2
N3 2S3 N N
NdNd
4 N24S
S1 S1
S2
S2
71(2)96(22)
103(2)61(8)
96(22)
178(7)
61(8)
178(7)97(3)
57(20)
51(2)
45(2)
105(9)
57(20)
55(6)
105(9)
91(3)
55(6)
69(20)
50(2)
46(2)
69(8)
69(20)
57(6)
69(8)
59(3)
57(6)
0
0
0
0
0
−6(17)
−4(1)
−6(1)−2(7)
−6(17)
11(5)
−2(7)
11(5)−3(2)
84(3)
97(3)140(3) 91(3)
58(38) 84(3)
138(42)
140(3)
58(38)
119(17) 138(42)
136(18)
119(17)
136(18)
208(13)
71(11)
208(13)
71(11)
55(3)
59(3)
74(42)
55(3)
74(42)
66(16)
66(16)
81(12)
81(12)
0
0
0
0
0
111(3)
58(3)
72(3)
145(3) 54(3)54(3)
72(3)
145(3)
72(3)
111(37) 126(40)
126(40) 93(37)
93(37)
111(37)
100(14)
100(14) 95(15)
95(15) 102(15)
102(15)
223(12)
50(9)
86(10)
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Compound
1
111(3)
58(3)
223(12)
50(9)
72(3)
86(10)
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
−3(2)−8(2)
−5(33)
−8(2)
−5(33)
−14(13)
−14(13)
29(9)
29(9)
−8(2)
−8(2)
−9(2)−9(2)
−48(31)
−48(31)
−11(11)
−11(11)
9(8)
9(8)
Given in the expression exp[−2π2 (a*2 h2 2 U211 2+ b*2 k2 U222 2+ c*2 l2 U33
+ 2b*c*klU23 + 2a*c*hlU13 + 2a*b*hkU12 )].
2 2
1
Given in the expression exp[−2π (a* h U11 + b* k U22 + c* l U33 + 2b*c*klU23 + 2a*c*hlU13 + 2a*b*hkU12)].
Figure
2. Lattice
parameters
b, c),
and
c), selected
distances
(d(Ln2–S″)),
and volumes
molar volumes
m) of
Figure
2. Lattice
parameters
(a, b,(a,
and
selected
distances
(d(Ln2–S”)),
and molar
(Vm ) of (V
the
the complete
4N2S3 (Ln
series
(Ln
=
La–Nd,
error
bars
with
a
percentage
of
0.5%)
versus
the
complete
A-type A-type
Ln4 N2 SLn
series
=
La–Nd,
error
bars
with
a
percentage
of
0.5%)
versus
the
ionic
3
ionic
radii
(r
i
)
of
the
trivalent
lanthanide
cations
[17].
radii (ri ) of the trivalent lanthanide cations [17].
Inorganics 2017, 5, 2
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Table
4. 4.
Selected
interatomic
distances
/◦ ) for
for the
the three
three members
membersof
ofthe
theLn
Ln4N
Table
Selected
interatomic
distances(d/pm)
(d/pm)and
andangles
angles((∡/°)
2S23S3
4N
series
(Ln
= =Ce–Nd)
series
(Ln
Ce–Nd)compared
comparedto
toA-type
A-type La
La44N22SS33. .
Ln1
Ln1
Ln2Ln2
N
N
Ln1Ln1
Ln1Ln1
Ln1
Ln1
Ln2
Ln2
–N
–N
–N’
–N’
–S1–S1
–S2–S2
–N –N
–S1–S1
–S2–S2
–S2’–S2’
–S2”
–S2″
–Ln1
–Ln1
–Ln1’
–Ln1’
–Ln2
–Ln2
–N–Ln1
–N–Ln1
–N–Ln2
–N–Ln2
−N–Ln2’
−N–Ln2’
–N–Ln2
–N–Ln2
(1×)
(1×)
(1×)
(1×)
(2×)
(2×)
(2×)
(2×)
(2×)
(2×)
(1×)
(1×)
(2×)
(2×)
(1×)
(1×)
(1×)
(1×)
(1×)
(1×)
(1
(1×)×)
(2×)
(2×)
(1×)
(1×)
(2×)
(2×)
(2×)
(2×)
(1×)
(1×)
La [7]
233.8(6)
233.8(6)
243.2(6)
243.2(6)
287.8(1)
287.8(1)
296.9(1)
296.9(1)
243.8(3)
243.8(3)
299.8(1)
299.8(1)
306.1(1)
306.1(1)
315.1(2)
315.1(2)
341.1(2)
341.1(2)
233.8(6)
233.8(6)
243.2(6)
243.2(6)
243.8(3)
243.8(3)
96.3(2)
96.3(2)
109.8(2)
109.8(2)
112.5(2)
112.5(2)
114.4(2)
114.4(2)
La [7]
Ce
230.9(5)
230.9(5)
239.4(4)
239.4(4)
287.4(1)
287.4(1)
291.9(1)
291.9(1)
240.5(3)
240.5(3)
297.8(1)
297.8(1)
301.4(1)
301.4(1)
307.9(2)
307.9(2)
350.5(2)
350.5(2)
230.9(5)
230.9(5)
239.4(4)
239.4(4)
240.5(3)
240.5(3)
96.7(2)
96.7(2)
109.6(1)
109.6(1)
112.5(1)
112.5(1)
114.4(2)
114.4(2)
Ce
Pr
Pr
229.6(9)
229.6(9)
236.1(9)
236.1(9)
285.1(1)
285.1(1)
289.5(2)
289.5(2)
238.7(5)
238.7(5)
296.2(1)
296.2(1)
298.9(2)
298.9(2)
305.4(3)
305.4(3)
349.8(3)
349.8(3)
229.6(9)
229.6(9)
236.1(9)
236.1(9)
238.7(5)
238.7(5)
97.2(3)
97.2(3)
109.4(2)
109.4(2)
112.8(2)
112.8(2)
113.9(4)
113.9(4)
Nd
Nd
227.6(8)
227.6(8)
236.4(8)
236.4(8)
283.1(1)
283.1(1)
288.1(2)
288.1(2)
237.0(5)
237.0(5)
294.4(1)
294.4(1)
297.4(2)
297.4(2)
306.0(3)
306.0(3)
342.8(3)
342.8(3)
227.6(8)
227.6(8)
236.4(8)
236.4(8)
237.0(5)
237.0(5)
96.5(3)
96.5(3)
109.7(2)
109.7(2)
112.7(2)
112.7(2)
114.1(3)
114.1(3)
InIn
analogy
to all
rare-earth
metal(III)
nitride
chalcogenides
and their
halidehalide
derivatives
known
analogy
to the
all the
rare-earth
metal(III)
nitride
chalcogenides
and their
derivatives
3
−
3+
to known
date [1–3],
the[1–3],
N the
anions
are again
by a more
or less
tetrahedron
of Ln
to date
N3− anions
are surrounded
again surrounded
by a more
or distorted
less distorted
tetrahedron
of
3
−
3+
cations,
in which
the four
N –Ln
(228–241
maximumofof1313pm
pmand
and
3+ distances
Ln3+ cations,
in which
the four
N3−–Lndistances
(228–241pm)
pm)differ
differ by
by a
a maximum
◦ and 114◦ (Table 4). In fact, the typical characteristic of the structural
thethe
angles
range
between
97
angles range between 97° and 114° (Table 4). In fact, the typical characteristic of the structural
9+ tetrahedra. As shown in
construction
constructionisisactually
actuallycreated
createdby
bythe
theindividual
individuallinkage
linkage of
of these
these [NLn
[NLn44]]9+ tetrahedra.
As shown in
9+
12+
9+
12+
Figure
3,
the
[NLn
]
units
initially
occur
as
dimers
[N
Ln
]
by
sharing
a
common
edge
(Ln1···Ln1),
Figure 3, the [NLn
4 4] units initially occur as dimers [N22 6] by sharing a common edge (Ln1···Ln1),
and
they
areare
then
condensed
to one-dimensional
infinite
strands
along
[001]
by by
corner-linkage
(via(via
Ln2)
and
they
then
condensed
to one-dimensional
infinite
strands
along
[001]
corner-linkage
1 {[N(Ln1)
e e (Ln2)v v ]3+
1
3+} (e
with
neighboring
unitsunits
corresponding
to to
(e
=
edge-linking,
{[N(Ln1)
(Ln2)
]
=
edge-linking,
Ln2)two
withsimilar
two similar
neighboring
corresponding
∞ ∞
2/2
2/22 / 2
2/2
9+ -tetrahedral linkage is also found in the crystal structures of
v =v vertex-linking).
linkage is also found in the crystal structures of
= vertex-linking).This
Thistype
typeofof[NLn
[NLn44]]9+-tetrahedral
thethe
nitride
chlorides
[18] and
and in
in those
those of
of nitride
nitride sulfide
sulfide halides
halidesLn
Ln6N
nitride
chloridesβ-Y
β-Y
2NCl
andβ-Gd
β-Gd22NCl33 [18]
3S
2 NCl
3 3and
6N
34SX4 X
(Ln(Ln
= La–Nd;
the crystal
crystalstructure
structureisismade
madeup
upofoftwo
twokinds
kinds
= La–Nd;XX==Cl,
Cl,Br)
Br)[19,20].
[19,20]. In
In the
the latter, however, the
of of
strands
each other
otheralong
alongtheir
theirpropagation
propagation
axis.
Figure
4 shows
strandsthat
thatare
arecommensurable
commensurable with each
axis.
Figure
4 shows
a
projection of the crystal
crystal structure
structure of the
the new
new Ln
Ln44N22SS33 representatives
2S23S3
a projection
representativeswith
withan
an A-type
A-type La
La4N
4N
1 1{([NLn
6+ double strands are separated by two
6+
structure
strands are separated by two
structurewith
witha aview
viewalong
alongthe
thec-axis.
c-axis. The
The ∞
∞ {([NLn22]22)) } }double
2
−
3+
2−
3+
crystallographically
with almost
almost octahedral
octahedralLn
Ln -coordination
-coordination
spheres
(Table
spheres
(Table
5).5).
crystallographicallydifferent
differentSS anions with
The
neighboring
in the
thea-direction
a-directionare
aresimilarly
similarly
oriented
se, but
compared
The
neighboringcationic
cationicchain
chain units in
oriented
perper
se, but
compared
to
to their
theiradjacent
adjacentchains
chainsininthe
theb-direction,
b-direction,they
theyget
getmirrored
mirroredbybya adiagonal
diagonalglide
glideplane
planen nthat
thatruns
runs
vertical
b-axis
heights
one-fourth
and
three-fourths
and
shifted
one-half
avertical
to to
thethe
b-axis
at at
heights
of of
one-fourth
and
three-fourths
and
areare
shifted
byby
one-half
in in
thethe
a- and
and c-directions,
respectively.
singleisstrand
is surrounded
total
of in
sixthe
more
in the
c-directions,
respectively.
Thus, aThus,
singleastrand
surrounded
by a totalby
of asix
more
manner
of a
manner of
a hexagonal
hexagonal
rod
packing. rod packing.
12+
Figure3.3.Linkage
Linkage of
4]9+]9+
units
via via
edges
to dimers
[N2Ln[N
6]12+Ln
and
their
linear
vertex
Figure
of tetrahedral
tetrahedral[NLn
[NLn
units
edges
to dimers
and
their
linear
4
2
6]
1
e
v
3+
1
e
v
3+
connection
to
{[N(Ln1)
(Ln2)
]
}
strands
along
[001]
in
the
crystal
structure
of
the
A-type
∞
2
/
2
2
/
2
vertex connection to ∞ {[N(Ln1)2/2 (Ln2)2/2 ] } strands along [001] in the crystal structure of the A-type
4N2S3 series (Ln = La–Nd).
LnLn
4 N2 S3 series (Ln = La–Nd).
Inorganics 2017,
2017, 5,
5, 22
Inorganics
of 10
10
66 of
Figure 4. Projection of the crystal structure of the A-type Ln N2 S3 series (Ln = La–Nd) on the [001] plane.
Figure 4. Projection of the crystal structure of the A-type4 Ln
4N2S3 series (Ln = La–Nd) on the [001]
plane.
Table 5. Motifs of mutual adjunction for the A- and B-type Ln4 N2 S3 structures (Ln = La–Nd).
Table 5. Motifs of mutual adjunction for the A- and B-type Ln4N2S3 structures (Ln = La–Nd).
Ln1
Ln2
Ln3
Ln4
C.N.
Ln1
Ln2
Ln4
C.N.
A-type Ln4 NLn3
2 S3
A-type Ln4N2S3
N
2/2
2/2
4
N
4
2/2
2/2
S1
2/4
1/2
6
S22/4
2/2 1/2
3+1/3+1
5+1
S1
6
S2
5+1
2/2
3+1/3+1
C.N.
6
6+1
6
6+1
C.N.
B-type Ln4 N2 S3
B-type Ln4N2S3
N1
1/1
1/1
1/1
1/1
4
N1
4
1/1
N21/1
1/1 1/1 1/1
1/1
1/1 1/1 4
N2
4
1/1
S11/1
1/2 1/1 1/2
1/2
0/0 1/1 6
S21/2
1/2 1/2 0/0
1/2
1/2 0/0 6
S1
6
1/2
S3
1/1
1/1
1/1
3/3
6
S2
6
1/2
0/0
1/2
1/2
S4
1/1
3/3
1/1
1/1
6
S3
6
1/1
1/1
1/1
3/3
C.N.
6
6
7
S4
6
1/1
3/3 7
1/1
1/1
6
7
6
7
C.N.
Apart from the nitride sulfides Ln4 N2 S3 (Ln = Ce–Nd) and La4 N2 S3 [7] of the orthorhombic A-type
modification
presented
here,sulfides
a monoclinic
for La
S34N
[12]
Pr4the
N2 Sorthorhombic
Apart from
the nitride
Ln4N2form
S3 (Ln(B-type)
= Ce–Nd)
and
2S3 and
[7] of
4 N2La
3 [9] has been
reported
for each with
a crystal structure
quite different
the orthorhombic
one.
Unlike
crystal
A-type
modification
presented
here, a monoclinic
formfrom
(B-type)
for La4N2S3 [12]
and
Pr4N2the
S3 [9]
has
structure
of the
Ln4 N
S3 members
(Lnquite
= La,different
Pr), in which
linear
chains are built
by linkage
been
reported
forA-type
each with
a 2crystal
structure
from the
orthorhombic
one. Unlike
the
12+ bitetrahedra, in the B-type structure layers are produced by their cross-linkage via
of
[N
Ln
]
crystal2 structure
of the A-type Ln4N2S3 members (Ln = La, Pr), in which linear chains are built by
6
2 {[N(Ln3/4)e (Ln1/2)v ]3+ } with four- and eight-fold pores (Figure 5).
12+ bitetrahedra,
commonofvertices
to ∞
linkage
[N2Ln6]according
in the B-type
2/2 structure
2/2 layers are produced by their cross-linkage
2the cell volume
e
3+
Accompanied
by
a
quadruplication
of
for the v2B-type
(Z = 8) as compared to the A-type
via common vertices according to ∞ {[N(Ln3/4) 2 / 2 (Ln1/2)
/ 2 ] } with four- and eight-fold pores
(Z = 2), 5).
theAccompanied
unit cell of theby
B-Ln
contains
four
times
the total
of cations
4 N2 S3 representatives
(Figure
a quadruplication
of the cell
volume
for
the B-type
(Znumber
= 8) as compared
and
anions,
but
only
twice
the
number
of
crystallographically
different
unkind
particles
owing
the
to the A-type (Z = 2), the unit cell of the B-Ln4N2S3 representatives contains four times the tototal
doubling
of
the
respective
Wyckoff
positions
(8f
and
4c
or
4e
as
compared
to
4g
and
2a).
With
the
number of cations and anions, but only twice the number of crystallographically different unkind
exceptionowing
of theto
already-mentioned
Ln2–S2”
which
loses its(8fcoordinative
upon
particles
the doubling of thedistance
respective
Wyckoff
positions
and 4c or 4e influence
as compared
tothe
4g
3− and S2− ) as well as the cations
transition
from
A-La
N
S
to
A-Ce
N
S
,
both
kinds
of
anions
(N
4 2 3 of the already-mentioned
4 2 3
and 2a). With the exception
distance Ln2–S2″ which loses its coordinative
can analogously
betransition
assigned to
each
other
respective
modifications
as shown
in Table
5. well
influence
upon the
from
A-La
4N2in
S3 their
to A-Ce
4N2S3, both
kinds of anions
(N3− and
S2−) as
as the cations can analogously be assigned to each other in their respective modifications as shown
in Table 5.
Inorganics 2017, 5, 2
Inorganics 2017, 5, 2
7 of 10
7 of 10
9+ units via edges to dimers [N Ln ]12+
12+ their initial linear vertex
Figure 5.
5. Linkage
Linkage of
Figure
of tetrahedral
tetrahedral [NLn
[NLn44]]9+ units
via edges to dimers [N22Ln6] , ,their
initial linear vertex
18+
2 2
3+
connection to quadruples
and their
their final
final vertex fusion
connection
quadruples [N
[N44Ln10
10]]18+ and
fusion to
to porous
poroussheets
sheets∞ {[NLn
4/2] 3+}}
4/2
∞ {[NLn
perpendicular to
to [001]
[001] consisting
consisting of
of fourfour- and
and eight-membered
eight-membered rings
rings in
in the
the crystal
crystal structure
structure of
of the
the
perpendicular
B-type Ln
Ln44N
N22SS3 3series
series(Ln
(Ln==La,
La,Pr).
Pr).
B-type
In addition to La
La44N22SS33 [7,12]
A-La44N22SS33-- and
[7,12] crystallizing
crystallizing dimorphously
dimorphously in the A-La
and in
in the
B-Pr
structures
and
Ce
4
N
2
Se
3
,
which
is
observed
either
with
the
4
N
2
Se
3
or
with
the
B-Pr44N
N22SS3-type
-type
structures
and
Ce
N
Se
,
which
is
observed
either
with
Nd
N
Se
or
with
3
4 2 3
4 2 3
Ce
4
N
2
Te
3
-type
arrangement,
now
the
next
nitride
sulfide
of
the
lanthanoids
with
the
composition
Ce4 N2 Te3 -type arrangement, now the next nitride sulfide of the lanthanoids with
Pr44N
N22SS3 3 can
can represent
represent both
both the
the AA- and
and B-type structures. In
In order
order to
to determine
determine the
the respective
high-pressure
high-pressure and/or
and/or high-temperature
high-temperaturephases,
phases, the
the theoretically
theoretically calculated
calculated densities
densities using
using X-ray
X-ray
diffraction
diffraction (D
(Dxx)) give
give at
at least
least uniform
uniform indications,
indications, even
even though
though they
they are
are not strong. With
With values
values of
5.426 [7] and 5.772 g/cm
g/cm33(Table
(Table 1)
1) the
the A-type Ln44N
N22SS33members
members(Ln
(Ln==La,
La,Pr)
Pr)show
show somewhat
somewhat larger
larger
33 [9], respectively, which are available for the
densities
as
compared
to
5.363
[12]
and
5.740
g/cm
densities
5.740 g/cm [9], respectively, which are available for
possible low-pressure and/or
and/or high-temperature
high-temperature phases
phases of
of the
the B-type
B-type representatives.
representatives. To
To what extent
these differences
differencesofof1.2%
1.2%and
and
0.6%
could
be significant
the reader
to determine.
As the
0.6%
could
be significant
is leftistoleft
theto
reader
to determine.
As the physical
physical
parts
of
the
preparation
methods
for
members
of
both
modifications
are
identical
parts of the preparation methods for members of both modifications are identical (seven days at (seven
900 ◦ C
days
at 900 °Cfused
in evacuated
fused silica
ampoules, see Experimental),
only
the chemical
conditions
in evacuated
silica ampoules,
see Experimental),
only the chemical
conditions
can provide
an
can
provide
an
explanation.
If
for
the
synthesis
of
the
A-type
Ln
4
N
2
S
3
representatives
(Ln
=
La–Nd),
explanation. If for the synthesis of the A-type Ln4 N2 S3 representatives (Ln = La–Nd), in addition
in
addition
to the
lanthanoid
metal
andazide
sulfur,
cesium
(CsN3) and lanthanide
the corresponding
to the
lanthanoid
metal
and sulfur,
cesium
(CsN
the corresponding
bromide
3 ) and azide
lanthanide
, Ln =asLa–Nd)
with
CsBr
as aused
fluxing
were used the
(seealkali
Experimental),
(LnBr3 , Ln =bromide
La–Nd)(LnBr
with 3CsBr
a fluxing
agent
were
(seeagent
Experimental),
metal and
the
metal
and
the halides
in the form
the triiodides
3 (Ln =
La, Pr),
sodium
(NaN
3)
the alkali
halides
in the
form
of the triiodides
LnIof3 (Ln
= La, Pr), LnI
sodium
azide
(NaN
fluxing
NaI
3 ) andazide
and
fluxing
varied for
preparation
B-type
Ln4Nin2Sthis
3 ones.
in this case,
the
varied
for theNaI
preparation
of the B-type
Ln4 N2of
S3 the
ones.
Whether,
case,Whether,
the intermediates
formed,
intermediates
formed,
as elemental
(causing
changestransport)
in pressure
or chemical
transport)
such as elemental
iodinesuch
(causing
changes iodine
in pressure
or chemical
or ternary
halides
(such as
or
halides
(such
3LnBr
or Na
3LnI
6 [22]
thecan
second
play a role can
Csternary
in the
firstas
orCs
Na
[22] in
in the
the first
second
case)
play
a in
role
only case)
be speculated.
3 LnBr6 [21]
3 LnI66 [21]
only be speculated.
3. Experimental
3. Experimental
As adapted from the standard methodology reported in [1], the new lanthanoid nitride sulfides
Ln4 NAs
(Ln = Ce–Nd)
arestandard
obtainedmethodology
by the reaction
of lanthanoid
metal
ChemPur:
99.9%)
with
from the
reported
in [1], the
new(Ln;
lanthanoid
nitride
sulfides
2 S3adapted
sulfur
ChemPur:
and by
lanthanoid
tribromide
(LnBr3 ;metal
prepared
CeO2 ,99.9%)
Pr6 O11with
and
Ln
4N2S(S;
3 (Ln
= Ce–Nd)99.9999%)
are obtained
the reaction
of lanthanoid
(Ln; from
ChemPur:
Nd2 O3(S;
(all:
Johnson-Matthey:
by the ammonium-bromide
method from
[23]) and
sulfur
ChemPur:
99.9999%)99.999%)
and lanthanoid
tribromide (LnBr3; prepared
CeOcesium
2, Pr6O11azide
and
(CsN
Ferak:
99.9%). On adding
cesium
bromide
(CsBr; ChemPur:
99.9%)
as flux
almost black,
Nd
2O33; (all:
Johnson-Matthey:
99.999%)
by the
ammonium-bromide
method
[23])
and cesium
azide
rod-shaped
single
crystals
the target
compounds
(Ln = Ce–Nd)
thatas
reflect
in the
(CsN
3; Ferak:
99.9%).
On of
adding
cesium
bromideLn
(CsBr;
99.9%)
flux strongly
almost black,
4 N2 S3ChemPur:
rod-shaped single crystals of the target compounds Ln4N2S3 (Ln = Ce–Nd) that reflect strongly in the
Inorganics 2017, 5, 2
8 of 10
incident light under a microscope are obtained after seven days at 900 ◦ C in evacuated torch-sealed
fused silica tubes.
Nonetheless, the process of the reaction according to
34 Ln + 27 S + 6 CsN3 + 2 LnBr3 → 9 Ln4 N2 S3 + 6 CsBr (Ln = Ce–Nd),
which can be classified as redox metathesis with the formation of CsBr as driving force, is not complete.
Besides some white amorphous parts, which are presumably produced by undesired reactions with
the silica-ampoule walls, mostly brown rods that could be characterized as Ln3 NS3 representatives
(Ln = Ce–Nd) [24] were also obtained. As in addition to this the whole product mixture in excess of
CsBr is stable to hydrolysis, so the fluxing agent and by-product can easily be rinsed off with water.
A largest possible black rod (0.02 × 0.03 × 0.20 mm3 ) of each of the new Ln4 N2 S3 members was selected
from the mixture under paraffin oil and transferred into a mark-tube capillary to subsequently record
the intensity data sets of X-ray diffraction experiments with the help of a plate detector (four-circle
diffractometer Kappa-CCD, Bruker AXS). In Tables 1–3 the crystallographic data for the three new
nitride sulfides Ln4 N2 S3 (Ln = Ce–Nd) are summarized.
4. Conclusions
The new series of lanthanoid(III) nitride sulfides with the composition Ln4 N2 S3 (Ln = Ce–Nd)
adopting the A-type structure of La4 N2 S3 [7] expands the knowledge about the constitution of
lanthanoid(III) nitride chalcogenides in general. Just like for all members of the formula types
Ln3 NCh3 [2,24] and Ln4 N2 Ch3 [4–12], nitride-centered lanthanoid tetrahedra [NLn4 ]9+ display the
fundamental building units, which are here connected by one edge (e) and two vertices (v) each
1 {([N(Ln1)e (Ln2)v ]3+ ) } chains. Bundled like hexagonal rod packing, they are held
to form ∞
2
2/2
2/2
together by S2− anions taking care of the charge compensation. Whereas the coordination numbers
(C.N. = 5–6) of these compare well with those in the binary sesquisulfides Ln2 S3 with A- or C-type
crystal structures (C.N. = 5–6) [25–29], the presence of tetrahedrally coordinated N3− anions baffles a
little, since all binary lanthanoid(III) mononitrides LnN [30,31] exhibit octahedrally coordinated N3−
anions in their rocksalt-type crystal structures.
Supplementary Materials: The following are available online at www.mdpi.com/2304-6740/5/1/2/s1, cif and
checkcif files of Ce4 N2 S3 , Nd4 N2 S3 , and Pr4 N2 S3 .
Acknowledgments: At this point the authors gratefully acknowledge the State of Baden-Württemberg (Stuttgart,
Germany), the Deutsche Forschungsgemeinschaft (Bonn, Germany) and the Fonds der Chemischen Industrie (Frankfurt
am Main, Germany) for considerable financial support.
Author Contributions: Falk Lissner conceived and performed the experiments; Falk Lissner recorded the intensity
data sets of X-ray diffraction experiments and analyzed the data; Falk Lissner and Thomas Schleid wrote the paper.
Conflicts of Interest: The authors declare no conflict of interest.
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