Cation-controled formation of N,N′-dialkylimidazolium cadmium-thiocyanate complexes: Synthesis and structural characterization

Article abstract of DOI:10.1016/S0022-4596(02)00063-4

Three new N,N′-dialkylimidazolium salts of cadmium-thiocyanate, [EtMeIm]₂[Cd₂(SCN)₆] (2), [C₆H₄(CH₂ImMe)₂][Cd(SCN) ₄] (3), [C₆Me₃(CH₂ImMe)₃][CdBr ₃(SCN)](NO₃) (4) have been prepared, and their crystal structures have been determined by X-ray diffraction. Crystal data: 2, monoclinic, C2/c, a = 18.349(4) A, b = 7.8667(18) A, c = 21.399(5) A. β = 110.346(4)°, V = 2896.1(11) A³, Z = 4, and R1 = 0.0561; 3, monoclinic, C2/c, a = 20.347(7) A, b = 14.029(5) A, c = 9.380(3) A, β = 112.034(6)°, V = 2482.1(15) A³, Z = 4, and R1 = 0.0397; 4, hexagonal, P6₃, a = b = 10.7634(8) A, c = 16.0315(17) A, V = 1608.4(2)A³, Z = 2, and R1 = 0.0569. Compound 2 consists of triply bridged infinite one-dimensional cadmium-thiocyanate chains, and two independent cadmium atoms are octahedrally coordinated in 2N4S and 4N2S geometry, respectively. In 3, the cadmium atom is octahedrally coordinated with two cis N-bonded monodentate NCS^- ligands and four bridging SCN^- in a S trans to S, and N trans to N coordination fashion, and thus form doubly bridged infinite one-dimensional chains. Whereas 4 is mononuclear, consisting of a discrete [C₆Me₃(CH₂ImMe)₃]³⁺ cation, a nitrate, and [CdBr₃(SCN)]^- ion, and each cadmium(II) ion is coordinated to three bromide and one nitrogen atom of SCN^- ion. The structures of these compounds are dictated by the imidazolium cations.

Full text of DOI:10.1016/S0022-4596(02)00063-4

Journal of Solid State Chemistry 169 (2002) 199–207
Cation-controled formation of N,N0-dialkylimidazolium cadmium–
thiocyanate complexes: synthesis and structural characterization
Fenghui Liu, Wanzhi Chen,* and Xiaozeng You
State Key Laboratory of Coordination Chemistry, Department of Chemistry, Institute of Coordination Chemistry, Nanjing University,
Nanjing 210093, People’s Republic of China
Received 4 June 2002; received in revised form 3 September 2002; accepted 25 September 2002
Abstract
Three new N,N0-dialkylimidazolium salts of cadmium–thiocyanate, [EtMeIm]2[Cd2(SCN)6] (2), [C6H4(CH2ImMe)2][Cd(SCN)4]
(3), [C6Me3(CH2ImMe)3][CdBr3(SCN)](NO3) (4) have been prepared, and their crystal structures have been determined by
X-ray diffraction. Crystal data: 2, monoclinic, C2=c; a ¼ 18:349ð4Þ A, b ¼ 7:8667ð18Þ A, c ¼ 21:399ð5Þ A, b ¼ 110:346ð4Þ1,
V ¼ 2896:1ð11Þ A3, Z=4, and R1 ¼ 0:0561; 3, monoclinic, C2=c; a ¼ 20:347ð7Þ A, b ¼ 14:029ð5Þ A, c ¼ 9:380ð3Þ A,
b ¼ 112:034ð6Þ1, V ¼ 2482:1ð15Þ A3, Z ¼ 4; and R1 ¼ 0:0397; 4, hexagonal, P63, a ¼ b ¼ 10:7634ð8Þ A, c ¼ 16:0315ð17Þ A,
V ¼ 1608:4ð2Þ A3, Z ¼ 2; and R1 ¼ 0:0569: Compound 2 consists of triply bridged infinite one-dimensional cadmium–thiocyanate
chains, and two independent cadmium atoms are octahedrally coordinated in 2N4S and 4N2S geometry, respectively. In 3, the
cadmium atom is octahedrally coordinated with two cis N-bonded monodentate NCSÀ ligands and four bridging SCNÀ in a S trans
to S, and N trans to N coordination fashion, and thus form doubly bridged infinite one-dimensional chains. Whereas 4 is
mononuclear, consisting of a discrete [C6Me3(CH2ImMe)3]3+ cation, a nitrate, and [CdBr3(SCN)]À ion, and each cadmium(II) ion
is coordinated to three bromide and one nitrogen atom of SCNÀ ion. The structures of these compounds are dictated by the
imidazolium cations.
r 2002 Elsevier Science (USA). All rights reserved.
Keywords: Cation control; Imidazolium; Thiocyanate; Cadmium complexes; Crystal structures
1. Introduction
thiocyanate exhibit anisotropic physical properties such
as NLO behavior [8–14]. The arrangement and align-
ment of one-dimensional coordination polymer chains
dominate their physical properties such as optoelectro-
nic and luminescence. Imidazolium salts are easily
prepared, and their size and symmetry can be easily
tuned by changing the N-substituents. Thus, the
utilization of imidazolium salts affords the opportunity
to explore the role of the counter cations in the
arrangement and alignment of the cadmium–thiocya-
nate chains [15].
The N,N0-dialkylimidazolium salts (also called ionic
liquids) are receiving growing interests recently since
they have proved to be good solvents, and their
deprotonated forms (i.e., heterocyclic carbene) reacts
with many transition metals [1, 2]. The interests also
arise from their distinct physicochemical properties
and potential applications in electrochemistry [3], extr-
action technology [4], and as liquid crystals [5].
A few dialkylimidazolium salts with the formula
[RR0Im][MXn] have been recently prepared and char-
acterized [6, 7]. Recently, it has been reported that some
hybrid materials involving polymeric anionic cadmium–
In this paper, we report the synthesis, characterization
and single-crystal X-ray structure of the imidazolium
salts, [EtMeIm]2[Cd2(SCN)6] (EtMeIm=N-ethyl-N0-
methylimidazolium) (2), [C6H4(CH2ImMe)2][Cd(SCN)4]
[(C6H4(CH2ImMe)2=p-bis(N,N0-methylimidazolyl)xy-
lylene)] (3), and [C6Me3(CH2ImMe)3][CdBr3(SCN)]
*Corresponding author. Villa Sanberunal 405, Shinjuku 7-3-5,
Shinjuku Ku, Tokyo 169-8555, Japan. Fax: +81-3-3209-8726.
E-mail address: chenwz@mn.waseda.ac.jp(W. Chen).
(NO3)
[C6Me3(CH2ImMe)3=1,3,5-tris(N,N0-methyl-
0022-4596/02/$ - see front matter r 2002 Elsevier Science (USA). All rights reserved.
PII: S 0 0 2 2 - 4 5 9 6 ( 0 2 ) 0 0 0 6 3 - 4

200
F. Liu et al. / Journal of Solid State Chemistry 169 (2002) 199–207
imidazolylmethyl)-2,4,6-trimethylbenzene] (4). The imi-
dazolium cations used are shown in Chart 1.
CH
3
N
CH
3
N
N
N
H C
3
N
N
N
H C
N
CH CH
3
N
2
3
N
N
H C
3
N
CH
3
p-bis(N,N'-methylimidazolyl)-
xylylene
1,3,5-tris(N,N'-
methylimidazolylmethyl)-2,4,6-
trimethylbenzene)
N,N'-ethylmethylimidazolium
2.4. Preparation of [C6H4(CH2ImMe)2][Cd(SCN)4], 3
2. Experimental section
2.1. Materials and methods
To a mixture of 1 mL of Cd(NO3)2 (1 mol/L) and
3 mL of KSCN (1 mol/L) in water was added
[C6H4(CH2ImMe)2]Cl2 (0.5 mmol). A white precipitate
was immediately formed. Acetone was added to the
above mixture till all the precipitate was dissolved. Slow
evaporation of the colorless solution afforded needle-
like crystals in 81% yield. Anal. calcd for
C20H20CdN8S4: C, 39.18; H, 3.29; N, 18.28%. Found:
C, 39.06; H, 3.44; N, 18.17%.
All the starting materials were reagent grade and used
without further purification. Elemental analyses were
1
performed on a PE 240C elemental analyzer. H NMR
spectra were acquired on a Bruker AM 400 (400 MHz)
spectrometer, using the deuterated solvent as the
lock and residual solvent as the internal reference.
[EtMeIm]Br and [C6H4(CH2ImMe)2]Cl2 were prepared
using the published procedure [16].
2.5. Preparation of
[C6Me3(CH2ImMe)3][CdBr3(SCN)](NO3), 4
2.2. Preparation of [C6Me3(CH2ImMe)3]Br3, 1
To a mixture of 1 mL of Cd(NO3)2 (1 mol/L) and
3 mL of KSCN (1 mol/L) in water was added [C6Me3
(CH2ImMe)3]Br3 ( 0.33 mmol) in 4 mL of acetone. The
mixture was allowed to stand at 51C. Colorless crystals
were grown after a week. Yield: 74%. Anal. calc for
C25H33Br3CdN8O3S: C, 34.21; H, 3.79; N, 12.77%.
Found: C, 33.70; H, 3.82; N, 12.54%.
To a solution of 1,3,5-tris(bromomethyl)-2,4,6-tri-
methylbenzene (4.0 g, 0.01 mol) in 20 mL of toluene was
added N-methylimidazole (4.1 g, 0.05 mol) slowly. Pale-
yellow solid was obtained by adding 20 mL of diethyl
ether to the mixture. Yield: 94%. Anal. calcd for
C24H33Br3N6: C, 44.67; H, 5.15; N, 13.02%. Found:
1
C, 44.33; H, 5.42; N, 12.79%. H NMR (D2O): 8.71 (s,
2.6. Crystallographic data collection and structure
determination
NCHN, 3H), 7.56, 5.65 (both br. NCHCHN, each 3H),
4.65 (s, CH2, 6H), 3.94 (s, NCH3, 9H), 2.41 (s, ArCH3,
9H).
Single-crystal X-ray diffraction measurements
of all compounds were carried out with a Bruker Smart
1000 CCD diffractometer equipped with a graphite
crystal monochromator situated in the incident beam
for data collection. The determination of unit-cell
parameters and data collections were performed with
MoKa radiation (l ¼ 0:71073 A). Unit-cell dimensions
were obtained with least-squares refinements and the
structure was solved by direct methods [17, 18]. The
final refinement was performed by full-matrix
least-squares methods with anisotropic thermal
parameters for non-hydrogen atoms on F2: The
hydrogen atoms were added theoretically, and riding
2.3. Preparation of [(EtMeIm)]2[Cd2(SCN)6], 2
To a mixture of 1 mL of Cd(NO3)2 (1 mol/L) and
3 mL of KSCN (1 mol/L) in water was added N-ethyl-
N0-methylimidazolium bromide (1 mmol). A white pre-
cipitate was immediately formed. Addition of acetone to
the resulted mixture till all the precipitate was dissolved.
Slow evaporation of the pale-yellow solution afforded
colorless prisms in 86% yield. Anal. calcd for
C18H22Cd2N10S6: C, 27.17; H, 2.79; N, 17.60%. Found:
C, 26.96; H, 3.02; N, 17.49%.

F. Liu et al. / Journal of Solid State Chemistry 169 (2002) 199–207
201
Table 1
Crystal data and structure refinement for 2, 3, and 4
2
3
4
Empirical formula
Formula weight
Crystal size (mm)
Crystal system
Space group
a (A)
C18H22Cd2N10S6
397.81
C20H20CdN8S4
613.08
C25H33Br3CdN8O3S
877.78
0.17 Â 0.27 Â 0.81
Monoclinic
C2=c
18.349(4)
7.8667(18)
21.399(5)
110.346(4)
2896.1(11)
123(2)
0.08 Â 0.10 Â 0.32
Monoclinic
C2=c
20.347(7)
14.029(5)
9.380(3)
112.034(6)
2482.1(15)
293(2)
0.43 Â 0.27 Â 0.21
Hexagonal
P6(3)
10.7634(8)
10.7634(8)
16.0315(17)
B (A)
c (A)
b (deg)
V (A)
T (K)
1608.4(2)
123(2)
2
Z
4
1.825
8340
4
1.641
7477
Dcalc (g/cm3)
Reflections collected
Reflections unique (Rint
Goodness-of-fit
R1 (I > 2sðIÞ)
wR2
1.812
10276
)
3255(0.0497)
1.029
0.0561
2842(0.0556)
0.974
0.0397
2233(0.1174)
1.338
0.0569
0.1526
0.1502
0.0973
Table 2
Atomic coordinates ( Â 104) and equivalent isotropic displacement
Table 3
Atomic coordinates ( Â 104) and equivalent isotropic displacement
parameters (A2 Â 103) for 2
parameters (A2 Â 103) for 3
a
Atom
x
y
z
Ueq
a
Atom
x
y
z
Ueq
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
Cd(1)
Cd(2)
N(1)
N(2)
N(3)
N(4)
N(5)
S(1)
1165(3)
533(4)
625(3)
2277(7)
1280(5)
1062(7)
1684(10)
1941(12)
2507(6)
0
9570(9)
7209(8)
11401(7)
4460(20)
3374(10)
3912(10)
5401(16)
4140(20)
3590(20)
8790(1)
10000
4151(3)
1280(3)
1539(3)
4128(9)
3346(4)
3832(4)
4927(5)
5442(9)
3012(9)
2500
33(1)
36(1)
28(1)
148(9)
52(2)
64(3)
118(6)
142(7)
204(14)
24(1)
27(1)
39(1)
46(1)
28(1)
76(3)
87(3)
42(1)
42(1)
48(1)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
C(10)
Cd(1)
N(1)
N(2)
N(11)
N(12)
S(1)
3954(2)
5813(2)
1946(2)
2168(2)
2792(2)
877(2)
7998(2)
5434(2)
6276(2)
6203(2)
6199(2)
6215(2)
6225(2)
5373(2)
7080(2)
6270(2)
6284(1)
7461(2)
5130(2)
6246(2)
6254(1)
8746(1)
6235(1)
8207(3)
11125(3)
8137(3)
6030(4)
7228(3)
5676(3)
6626(3)
7078(3)
7066(3)
10126(3)
7500
22(1)
22(1)
20(1)
22(1)
24(1)
23(1)
20(1)
21(1)
24(1)
27(1)
19(1)
29(1)
31(1)
20(1)
18(1)
26(1)
23(1)
424(2)
217(1)
212(2)
3172(2)
5000
0
0
À1019(3)
439(4)
453(3)
1638(5)
2053(4)
1401(1)
669(1)
861(1)
10177(8)
7791(8)
10856(6)
4547(10)
3728(11)
8713(3)
6335(2)
12234(3)
411(2)
762(3)
1968(2)
4324(3)
3530(5)
3549(1)
2012(1)
931(1)
4373(1)
4413(1)
2646(1)
1641(1)
3354(1)
6150(1)
8130(3)
8293(3)
8547(3)
6615(3)
8303(1)
10308(1)
S(2)
S(3)
S(2)
a Ueq is defined as one-third of the trace of the orthogonalized Uij
tensor.
a Ueq is defined as one-third of the trace of the orthogonalized Uij
tensor.
on the concerned atoms and refined with fixed thermal
factors. Crystallographic data and experimental details
for structural analyses are summarized in Table 1. The
atomic coordinates of compounds 2, 3, and 4 are given
in Tables 2–4.
thiocyanate coordination polymers exhibit promising
NLO properties. The combination of dialkylimidazo-
lium (ionic liquid) and cadmium–thiocyanate complexes
may create new physicochemical properties. The imida-
zolium halide can be easily prepared by either the
quarterization of N-alkylimidazole with organic halide
or the condensation of glyoxal, paraformaldehyde, and
primary amines. Three imidazolium salts of cadmium–
thiocyanate were prepared by metathesis reactions
between cadmium–thiocyanate anions and imidazolium
halide in water. They are isolated as white or pale-yellow
3. Results and discussion
3.1. Preparation of the complexes
Interest in these inorganic–organic hybrid materials
was raised by the observation that some cadmium–

202
F. Liu et al. / Journal of Solid State Chemistry 169 (2002) 199–207
Table 4
Atomic coordinates ( Â 104) and equivalent isotropic displacement
parameters (A2 Â 103) for 4
a
Atom
x
y
z
Ueq
Br(1)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
Cd(1)
N(1)
N(2)
N(3)
N(4)
O(1)
S(1)
8822(1)
6667
5731(1)
3333
1540(1)
À891(12)
4269(4)
4253(4)
4191(6)
4350(5)
3478(6)
2828(5)
2664(6)
1418(7)
1051(1)
À410(20)
3560(4)
2283(4)
488(5)
40(1)
25(3)
31(1)
34(2)
47(2)
43(2)
41(2)
46(2)
44(2)
62(3)
30(1)
61(5)
35(1)
41(2)
45(2)
149(13)
62(2)
6678(9)
7981(9)
9353(11)
6695(11)
7807(9)
6314(11)
7654(9)
6385(14)
6667
4635(8)
4638(8)
6009(10)
6036(9)
8299(9)
6287(9)
8628(9)
7242(11)
3333
6667
3333
6965(8)
6743(8)
10000
6841(7)
7344(7)
10000
8881(17)
6667
9250(30)
3333
109(12)
À2030(3)
a Ueq is defined as one-third of the trace of the orthogonalized Uij
tensor.
solids. The formation of [EtMeIm]2[Cd2(SCN)6] (2) is
expected since the [Cd(SCN)3]À chain is commonly
formed at the Cd/SCN ratio of 3 [15]. In the case of
[C6H4(CH2ImMe)2]2+, the complex of the formula
[C6H4(CH2ImMe)2][Cd(SCN)4] (3) was obtained as
the sole isolated compound at the same Cd/SCN
ratio. Surprisingly, when [C6Me3(CH2ImMe)3]3+ was
employed under the same reaction conditions,
[CdBr3(SCN)]2À is the only identified cadmium species.
Their composition was determined by elemental analy-
sis, and further confirmed by X-ray diffraction analysis.
Fig. 1. ORTEP drawing of 2 with thermal ellipsoids at 30%
probability level. The hydrogen atoms are omitted for clarity.
Table 5
Selected bond lengths (A) and angles (deg) for 2
Cd(1)–S(1)
Cd(1)–N(3)
Cd(2)–N(2)
C(1)–N(1)#1
C(3)–N(3)
C(2)–S(2)
2.7635(16) Cd(1)–S(2)
2.6865(16)
2.331(5)
2.7130(17)
1.154(8)
1.642(6)
1.644(5)
2.300(5)
2.327(6)
1.162(8)
1.150(7)
1.649(6)
Cd(2)–N(1)
Cd(2)–S(3)
C(2)–N(2)
C(1)–S(1)
C(3)–S(3)
N(1)#1–C(1)–S(1)
N(3)–C(3)–S(3)
N(3)–Cd(1)–S(2)#1 173.33(12)
178.1(5)
178.3(6)
N(2)–C(2)–S(2) 178.7(6)
N(3)–Cd(1)–N(3)#1 90.1(2)
3.2. X-ray crystal structure of
[EtMeIm]2[Cd2(SCN)6], 2
N(3)–Cd(1)–S(2) 91.29(13)
N(3)–Cd(1)–S(1)#1 90.46(12)
S(2)#1–Cd(1)–S(2)
S(2)–Cd(1)–S(1)#1
S(2)–Cd(1)–S(1)
88.09(8)
95.19(6)
82.98(6)
The structure of compound 2 is shown in Fig. 1, and
selected bond lengths and angels are collected in Table 5.
The cadmium and thiocyanate ions form triply bridged
one-dimensional infinite polymeric chains; two indepen-
dent Cd atoms are octahedrally coordinated in a 4N2S
and 2N4S coordination environment, respectively. This
is quite different from other one-dimensional infinite
cadmium–thiocyanate polymers, in which the cadmium
atoms are normally coordinated by three N atoms and
three S atoms in a fac configuration, and all the nitrogen
atoms are trans to the sulfur atoms around Cd center,
dictated by trans effect [8, 18, 19]. The average Cd–S and
Cd–N lengths are 2.721 and 2.319 A, the average Cd–S–
C and Cd–N–C angels are 97.871 and 146.931, respec-
tively which are consistent with those of other reported
cadmium–thiocyanate compounds [8–15]. The N–C–S
bridging ligands are almost linear with an average angle
N(3)–Cd(1)–S(1)
91.32(12)
S(1)#1–Cd(1)–S(1) 177.48(8)
N(2)–Cd(2)–N(1)#2 95.3(2)
N(1)#2–Cd(2)–N(1) 180.0(3)
N(1)–Cd(2)–S(3)#2 88.68(15)
N(2)–Cd(2)–N(2)#2 180.0
N(2)–Cd(2)–N(1)
N(2)–Cd(2)–S(3)#2 90.13(17)
84.7(2)
N(2)–Cd(2)–S(3) 89.87(17)
S(3)#2–Cd(2)–S(3) 180.00(6)
N(1)–Cd(2)–S(3) 91.32(15)
C(1)#1–N(1)–Cd(2) 135.9(5)
C(2)–N(2)–Cd(2)
C(1)–S(1)–Cd(1)
C(3)–S(3)–Cd(2)
150.2(5)
101.7(2)
94.4(2)
C(3)–N(3)–Cd(1)
C(2)–S(2)–Cd(1)
154.7(4)
97.5(2)
Note: Symmetry transformations used to generate equivalent atoms:
#1 Àx; y; Àz þ 1=2; #2 Àx; Ày þ 2; Àz:
of 178.41, and the average C–S and C–N bond lengths of
1.634 and 1.151 A, respectively.
As far as the alignments of chains are concerned, the
cadmium atoms are triply bridged by SCNÀ ions, and

F. Liu et al. / Journal of Solid State Chemistry 169 (2002) 199–207
203
(a)
(b)
Fig. 2. Perspective view of the stacking of the infinite [Cd(SCN)3]À chains: (a) along the crystallographic a-axis and (b) along the crystallographic
c-axis.
thus form infinite zigzag chains. The Cd?Cd distance is
B5.385 A, and the Cd?Cd?Cd angle is 164.721,
respectively. The adjacent chains are parallel to each
other running along the crystallographic a-axis
(Fig. 2(a)). The infinite chains form approximate hex-
agonal array along the crystallographic c-axis, and three
neighboring chains consist of triangular channels, which
are occupied by imidazolium cations, as shown in
Fig. 2(b). The imidazolium cations interact with anionic
cadmium–thiocyanate chains through weak hydrogen

204
F. Liu et al. / Journal of Solid State Chemistry 169 (2002) 199–207
bonding, C(4)–H(4)?S(1) (2.893 A) and electronic
interactions. Hexagonal arrangement is also adopted
by anionic [Cd(SCN)3]À chains in [(12C4)2Na]
[Cd(SCN)3] [8, 10], [R4N][Cd(SCN)3] [19, 20].
Cadmium atoms are bridged by two SCNÀ ions, one
of them is S-coordinated and other is N-coordinated to
the same metal atom, thus form a infinite polymeric
zigzag chain structure, with Cd?Cd distances of
5.914 A. The infinite [Cd(SCN)4]2À zigzag chains align
in a parallel manner (Fig. 4(a)), resulting in a space
group C2=c: The H(3) and H(4) of the imidazolium ring
forms hydrogen bonds with S atoms of coordinated
SCNÀ ions. Probably, the weak hydrogen bonding
interactions, C3–H(3)?S(1) (2.7573 A) and C(4)–
H(4)?S(1) (2.8752 A), play some role in the formation
of the unique chain polymer. The atoms of doubly
bridging SCNÀ ions, together with the cadmium ion on
3.3. X-ray crystal structure of
[C6H4(CH2ImMe)2][Cd(SCN)4], 3
X-ray
diffraction
analysis
revealed
that
[C6H4(CH2ImMe)2][Cd(SCN)4] (3) consist of infinite
one-dimensional chains of repeated [Cd(SCN)4]2À units
and discrete [C6H4(CH2ImMe)2]2+ cations. Within the
anionic chain, each cadmium atom is octahedrally
coordinated with two cis N-bonded monodentate NCSÀ
ligands and four bridging SCNÀ in a S trans to S, and N
trans to N coordination manner. Fig. 3 shows the
ORTEP plots of the cation and [Cd(SCN)4]2À anion.
Selected bond lengths and angles are summarized in
Table 6. The Cd–N [2.295(3) A] bond lengths of the
monodentate SCNÀ is the same as that of the bridging
SCNÀ [2.295(3) A], whereas the C–N and C–S bond
lengths of monodentate SCNÀ are slightly longer and
shorter than those of the bridging SCNÀ in the same
compound, respectively. In general, all the bond lengths
and angles are in the normal range as those in other
cadmium–thiocyanate compounds. Although 4N2S-
hexacoordinated doubly bridged cadmium compounds
are known [19, 21–26]. Compound 3 is the first example
of cadmium–thiocyanate complexes having two cis
monodentate SCNÀ ions.
Table 6
Selected bond lengths (A) and angles (deg) for 3
Cd(1)–N(1)
Cd(1)–S(2)
C(1)–N(1)
C(1)–S(1)
2.295(3) Cd(1)–N(2)
2.7916(10) C(2)–S(2)
2.295(3)
1.648(3)
1.151(4)
1.162(4)
1.637(3)
C(2)–N(2)#1
N(1)–C(1)–S(1)
179.2(3)
N(2)#1–C(2)–S(2)
N(2)–Cd(1)–N(1)
N(1)–Cd(1)–N(1)#3 88.00(13)
179.0(3)
90.95(11)
N(2)–Cd(1)–N(2)#3
N(2)#3–Cd(1)–N(1)
N(2)–Cd(1)–S(2)#3
90.32(15)
176.30(8)
86.25(7)
N(1)–Cd(1)–S(2)#3
N(2)–Cd(1)–S(2)
84.85(7)
91.77(7)
N(1)#3–Cd(1)–S(2)#3 97.18(7)
N(1)#3–Cd(1)–S(2)
C(1)–N(1)–Cd(1)
C(2)–S(2)–Cd(1)
84.85(7)
167.3(2)
96.17(10)
S(2)#3–Cd(1)–S(2) 177.19(3)
C(2)#1–N(2)–Cd(1) 171.1(2)
Note: Symmetry transformations used to generate equivalent atoms:
#1 Àx þ 2; Ày þ 2; Àz þ 1; #2 Àx; y; Àz þ 3=2; #3 Àx þ 2; y; Àz þ 1=2:
Fig. 3. ORTEP drawing of 3 with thermal ellipsoids at 30% probability level. The imidazolium cation, hydrogen atoms are omitted for clarity.

F. Liu et al. / Journal of Solid State Chemistry 169 (2002) 199–207
205
(a)
(b)
Fig. 4. Perspective view of the stacking of the infinite [Cd(SCN)4]2À chain: (a) along the crystallographic a-axis and (b) along the crystallographic
c-axis.

206
F. Liu et al. / Journal of Solid State Chemistry 169 (2002) 199–207
both sides, constitute an eight-membered ring. As shown
in Fig. 4(b), the [Cd(SCN)4]2À chains form tetragonal
channels running along the crystallographic c-axis. The
channels are filled by the [C6H4(CH2ImMe)2]2+ cations.
mium(II) ion is coordinated to three bromide ions and
one nitrogen atom of SCNÀ ion. The bond distances
and angles of imidazolium cation are all in normal
range. The C–S bond distance [1.582(14) A] is much
shorter than those in 2 and 3; the Cd–N [2.221(19) A]
distance is slightly shorter than those in 2 and 3.
Whereas the Cd–Br bond distance [2.5756(10) A] is
much shorter than that in the polymeric
[CdBr2(H2biim)] [2.7020(13) A and 2.8921(11) A] [27],
3.4. X-ray crystal structure of
[C6Me3(CH2ImMe)3][CdBr3(SCN)](NO3), 4
The structure of the complex [C6Me3(CH2Im-
Me)3][CdBr3(SCN)](NO3), together with the atomic
numbering scheme, is shown in Fig. 5. Important bond
distances and angles are given in Table 7. The structural
study shows that the complex is mononuclear, consisting
of a discrete [C6Me3(CH2ImMe)3]3+ cation, a nitrate
and [CdBr3(SCN)]2À ion. The nitrate ion was not well
solved possibly due to severe disorder, although the
diffraction data were repeatedly collected. Each cad-
[CdLBr2]
(L=2-formylpyrrole
thiosemicarbazone,
[2.589(1) and 2.637(1) A] [28], but matches that in
[CdBr2L2] [L=Ph3P+ (CH2)3COÀ2 , 2.580 (2) A] [29].
An interesting structural feature of complex 4 is that the
imidazolium cation, [C6Me3(CH2ImMe)3]3+ displays a
crown-like conformation, and the [CdBr3(SCN)]2À
anion constitute a tripod clothes stand.
In summary, the three inorganic–organic hybrid
materials have been characterized by X-ray crystal-
lographic diffraction. The N,N0-dialkylimidazolium
cadmium–thiocyanate complexes were prepared under
the same conditions. The structural analyses clearly
reveal that the variation of the imidazolium cations led
to three quite different complexes. It suggests that the
different imidazolium cations direct the formation of
this kind of complexes, the arrangement of chains, and
the coordination motif. It illustrates that the size,
symmetry as well as the charge number of the cations
play important role in the assembly of cadmium–
thiocyanate complexes.
4. Supplementary materials
Crystallographic data for the structural analyses have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC Nos. À169280, À175403, and
À175404 for compounds 2–4, respectively. Copies of
this information can be obtained free of charge from
The Director, CCDC, 12 Union Road, Cambridge, CB2
1EZ, UK (fax: +44-1223-336033; e-mail: depos-
it@ccdc.cam.ac.uk or http//www.ccdc.cam.ac.uk).
Fig. 5. ORTEP drawing of
4 with thermal ellipsoids at 30%
probability level. The hydrogen atoms and nitrate are omitted for
clarity.
Acknowledgments
The authors are grateful to the National Natural
Science Foundation of China for financial support.
Table 7
Selected bond lengths (A) and angles (deg) for 4
Cd(1)–N(1)
C(1)–N(1)
2.221(19) Br(1)–Cd(1)
C(1)–S(1)
2.5756(10)
1.582(14)
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