Syntheses and structure characterization of four inorganic-organic hybrid solids based on N-containing aromatic Brnsted bases and chlorometallates

Article abstract of DOI:10.1080/00958972.2012.686611

Four organic-inorganic hybrid complexes ([(HL1)₂SnCl ₆]·2H₂O (1) (L1=2-methylquinoline), [(HL2) ₂(CdCl₄)]·2H₂O (2) (L2=5,7-dimethyl-1,8- naphthyridine-2-amine), [(H₂L2)₂SnCl₆]2(Cl) (3), and [(H₂L3)SnCl₆]·2H₂O (4) (L3=3,6-bis(imidazol-1-yl)pyridazine)) derived from N-containing aromatic Brnsted bases and metal(II) chloride dihydrate (tin(II) chloride dihydrate and cadmium(II) chloride dihydrate) were prepared and characterized by IR, X-ray structure analysis, elemental analysis, and TG analysis. The aromatic rings of the cations in all of the compounds are essentially planar. X-ray diffraction analysis revealed that 2-4 have 3-D network structures built from hydrogen bonds between the cations and chlorometallates. Water molecules also play important roles in structure extension in 1, 2, and 4. The arrangements of the anions and cations in their solid state are dominated by shape, size, and symmetry of the cations and the different structures of the chlorometallates as well as by hydrogen-bond interactions.

Full text of DOI:10.1080/00958972.2012.686611

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Syntheses and structure
characterization of four
inorganic–organic hybrid solids based
on N-containing aromatic Brønsted
bases and chlorometallates
a
b
Shouwen Jin & Daqi Wang
a
TianMu College, ZheJiang A & F University, Lin’An 311300, P.R.
China
b
Department of Chemistry, Liaocheng University, Liaocheng
52059, China
2
Version of record first published: 10 May 2012.
To cite this article: Shouwen Jin & Daqi Wang (2012): Syntheses and structure characterization
of four inorganic–organic hybrid solids based on N-containing aromatic Brønsted bases and
chlorometallates, Journal of Coordination Chemistry, 65:11, 1937-1952
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Journal of Coordination Chemistry
Vol. 65, No. 11, 10 June 2012, 1937–1952
Syntheses and structure characterization of four
inorganic–organic hybrid solids based on N-containing
aromatic Brønsted bases and chlorometallates
SHOUWEN JIN*y and DAQI WANGz
yTianMu College, ZheJiang A & F University, Lin’An 311300, P.R. China
zDepartment of Chemistry, Liaocheng University, Liaocheng 252059, China
(
Received 7 June 2011; in final form 12 March 2012)
Four organic–inorganic hybrid complexes ([(HL1)
(HL2) (CdCl O (2) (L2 ¼ 5,7-dimethyl-1,8-naphthyridine-2-amine), [(H
)]ꢀ 2H
3), and [(H L3)SnCl (4) (L3 ¼ 3,6-bis(imidazol-1-yl)pyridazine)) derived from
] ꢀ 2H
2
SnCl
6
] ꢀ 2H
2
O (1) (L1 ¼ 2-methylquinoline),
[
2
4
2
2
L2) SnCl
2
6
] ꢀ 2(Cl)
(
2
6
2
O
N-containing aromatic Brønsted bases and metal(II) chloride dihydrate (tin(II) chloride dihydrate
and cadmium(II) chloride dihydrate) were prepared and characterized by IR, X-ray structure
analysis, elemental analysis, and TG analysis. The aromatic rings of the cations in all of the
compounds are essentially planar. X-ray diffraction analysis revealed that 2–4 have 3-D network
structures built from hydrogen bonds between the cations and chlorometallates. Water molecules
also play important roles in structure extension in 1, 2, and 4. The arrangements of the anions and
cations in their solid state are dominated by shape, size, and symmetry of the cations and the
different structures of the chlorometallates as well as by hydrogen-bond interactions.
Keywords: Tin; Cadmium; Crystal structure; N-Containing aromatic Brønsted bases;
Inorganic–organic hybrid
1. Introduction
Organic–inorganic hybrid materials represent new directions in solid-state chemistry
1, 2]. Organic–inorganic hybrids exhibit diverse structures, improved properties, and
[
functions unobserved in purely inorganic or organic phases, such as magnetic [3],
electrical [4–6], and optical properties [7]. Organic–inorganic hybrid materials may have
applications in fuel cells [8], liquid crystal-material development [9], nonlinear optics
[
10], and drug delivery [11].
Organic–inorganic hybrid compounds based on layers of anionic transition metal(II)
halogen frameworks and organic ammonium cations have been reported. For instance,
2
-D systems, (RNH ) M(II)X or (NH RNH )M(II)X (M ¼ Pb, Sn, Cu, etc.; X ¼ I,
3
2
4
3
3
4
Br, Cl; R ¼ alkyl, phenyl, etc.), have been studied in the field of low-dimensional
magnetism [12]. Structural transitions in hybrids containing long-chain alkylammonium
cations were studied to better understand biological lipid bilayers [13]. Most of the
*
Corresponding author. Email: shouwenjin@yahoo.cn
Journal of Coordination Chemistry
ISSN 0095-8972 print/ISSN 1029-0389 online ß 2012 Taylor & Francis
http://dx.doi.org/2710.1080/00958972.2012.686611

1
938
S. Jin and D. Wang
N
N
N
N
N
N
H N
N
N
2
N
L3
L2
Scheme 1. The N-containing aromatic Brønsted bases.
L1
ammonium cations incorporated in hybrid materials were either alkylammonium or
single-ring aromatic ammonium cations.
Metal halides such as SnX (X ¼ Cl, Br, and I) have been studied as semi-conducting
2
components [14] in organic–inorganic hybrid semiconductors, demonstrating potential
applications in display and storage technologies because of their stable exciton,
1
0
excellent film processability, and superior carrier mobility [15]. Cd(II), being a d
electron configuration, exhibits intriguing structural and photoluminescent properties
16]. Chlorocadmate(II) compounds represent a class of materials with unusual
[
structures [17], where the ligands are chlorides and water, if present, giving rise to
polymeric inorganic anions characterized by 1-D chains or 2-D layers. The presence of
organic cations (commonly protonated amines) as spacers between the inorganic anions
confers chemical flexibility on the compounds and enables the distances within the
chains or the layers to be modulated. In these complexes, the frameworks of
organoammonium cations and inorganic species are stabilized by hydrogen bonds
and Coulombic attractions. The energetics of N–Hꢀ ꢀ ꢀCl–M hydrogen bonds and their
possible role in supramolecular chemistry of inorganic–organic hybrid solids have been
described in detail [18].
L1–L3 (L1 ¼ 2-methylquinoline, L2 ¼ 5,7-dimethyl-1,8-naphthyridine-2-amine and
L3 ¼ 3,6-bis(imidazol-1-yl)pyridazine) are Brønsted bases with one to four nitrogen
atoms that can be protonated. When protonated the cations of L1–L3 are good donors
for hydrogen bonds. The three bases all have aromatic units which may give aromatic
stacking interactions. Thus carrying out the reaction between the N-containing
aromatic bases and chlorometallates in acidic conditions may display different non-
bonding interactions of these different functional groups. As an extension of our
research of organic–inorganic hybrid complexes based on imidazole derivatives [19],
herein we report the synthesis and structure of four chlorometallate complexes with
N-containing aromatic Brønsted bases (scheme 1) as organic ammonium cations.
2
2
. Experimental
.1. Materials
L2 and L3 were prepared according to modified procedures [20, 21]. The other
chemicals and solvents were of reagent grade and used as obtained from J & K
Chemical Ltd.

N-Containing aromatic bases and chlorometallates
.2. Physical measurements and analyses
1939
2
ꢁ
Elemental analyses (C, H, and N) were determined with a Perkin-Elmer 2400 C
instrument, and infrared (IR) spectra were measured as KBr pellets using a Nicolet
5
Delta Series TA-SDT Q600 in nitrogen between room temperature and 800 C (heating
DX FX-IR spectrophotometer. Thermogravimetric analyses (TGA) were studied by a
ꢁ
ꢁ
ꢂ1
rate 10 C min ) using Al crucibles.
2
2
.3. Preparation of the compounds
.3.1. Preparation of 5,7-dimethyl-1,8-naphthyridine-2-amine (L2). 2,6-Diaminopyridine
(21.8 g, 20.0 mmol), 2,4-pentanedione (21.0 g, 21.0 mmol), and powdered
anhydrous ZnCl (11.0 g, 80.0 mmol) were mixed, then refluxed with stirring for 10 h.
2
The reaction mixture was added slowly with good stirring and ice bath cooling to 15 g of
sodium hydroxide in 60 mL water. The brown solid was filtered after the solution
ꢁ
cooled overnight at 5 C, then was washed twice with cold water and dried. The crude
material was recrystallized from CHCl3 to give light yellow needles. Yield:
1
1.8 g, 34.2%.
2.3.2. Preparation of 3,6-bis(imidazol-1-yl)pyridazine (L3). Imidazole (4.5 g, 66 mmol)
ꢁ
was dissolved in anhydrous DMF (20 mL) and cooled to ca 5 C, then oil-free NaH
(1.6 g, 66.6 mmol) was added portionwise. When all of the NaH was added, the solution
was stirred for another 1 h to ensure complete reaction of NaH. Then 3,6-
dichloropyridazine (4.5 g, 30 mmol) dissolved in 30 mL DMF was added. The reaction
mixture was refluxed for 8 h, cooled to room temperature, and added to ice water. The
resulting brown product was isolated by vacuum filtration and recrystallized from
DMF to give prism crystals. Yield: 3.53 g, 56%.
2
.3.3. Preparation of [(HL1) (SnCl )] 2H O (1). Tin(II) chloride dihydrate (23.5 mg,
2
.
2
6
0
.10 mmol) dissolved in 1 mL of conc. hydrochloric acid and 3 mL of water was treated
with L1 (28.6 mg, 0.2 mmol). After stirring for several minutes, the solution was filtered.
The clear solution stood at room temperature for several days to give colorless block
crystals. Yield: 40 mg, 60.99% (based on SnCl ꢀ 2H O). Anal. Calcd for
2
2
C H Cl N O Sn (655.80) (%): C, 36.59; H, 3.66; N, 4.27. Found (%): C, 36.53; H,
2
0
24
6
2
2
ꢂ1
3
1
5
.58; N, 4.22. IR (KBr disc, cm ): 3566s, 3326s, 3224m, 3136s, 1609s, 1524s, 1448s,
349s, 1322w, 1208w, 1162w, 1088w, 967m, 892w, 830w, 789w, 760w, 685w, 586w,
52w.
2
.3.4. Preparation of [(HL2) (CdCl )] 2H O (2). L2 (5,7-dimethyl-1,8-naphthyridine-
2
.
2
4
2
-amine, 34.8 mg, 0.2 mmol) dissolved in 3 mL of conc. hydrochloric acid and 5 mL of
water was treated with cadmium(II) chloride dihydrate (46 mg, 0.20 mmol). After
stirring for several minutes, the solution was filtered. The clear solution stood at room
temperature for several days to give colorless block crystals. Yield: 55 mg, 86.12%
(based on L2). Anal. Calcd for C H CdCl N O (638.68): C, 37.58; H, 4.38; N, 13.15.
Found: C, 37.55; H, 4.36; N, 13.08. IR (KBr disc, cm ): 3520s, 3370s, 3280s, 3200s,
20 28 4 6 2
ꢂ1

1
940
S. Jin and D. Wang
3
8
120s, 3040s, 1612s, 1573s, 1528s, 1446s, 1357s, 1318w, 1212w, 1168w, 1110w, 970w,
94w, 835w, 780w, 720w, 682w, 610m.
.
.3.5. Preparation of [(H L2) SnCl ] 2(Cl) (3). The compound was prepared by the
2
2
2
6
similar procedure as for 2 from tin(II) chloride dihydrate (47 mg, 0.20 mmol) and 5,7-
dimethyl-1,8-naphthyridine-2-amine (34.8 mg, 0.2 mmol) in 4 mL of conc. hydrochloric
acid, and 3 mL of water. The compound was isolated as pale yellow block crystals.
Yield: 67 mg, 89% (based on L2). Anal. Calcd for C H Cl N Sn (752.76): C, 31.88; H,
2
0
26
8
6
ꢂ1
3.45; N, 11.16. Found: C, 31.84; H, 3.41; N, 11.11. IR (KBr disc, cm ): 3321s, 3297s,
3137s, 2976m, 1615s, 1524s, 1451s, 1382 s, 1329w, 1204w, 1162w, 1099w, 974w, 898w,
829w, 797w, 764w, 686w, 606w.
2
.3.6. Preparation of [(H L3)SnCl ] 2H O (4). The compound was prepared by
6 2
.
2
similar procedure to that for 2 from tin(II) chloride dihydrate (23.5 mg, 0.10 mmol) and
L3 (21 mg, 0.10 mmol) in 5 mL of conc. hydrochloric acid, and 8 mL of water. The
compound was isolated as colorless block crystals. Yield: 39 mg, 67.05%. Anal. Calcd
for C H Cl N O Sn (581.66): C, 20.63; H, 2.41; N, 14.44. Found: C, 20.59; H, 2.36;
1
0
14
6
6
2
ꢂ1
N, 14.42. IR (KBr disc, cm ): 3508m, 3342m, 3208s, 3134m, 3046m, 2922m, 2634m,
1
1
876m, 1696m, 1614m, 1538m, 1509m, 1452m, 1416m, 1334m, 1226m, 1136m, 1066m,
015m, 956m, 834m, 708m, 645m, 602m.
2
.4. X-ray crystallography
Single-crystal X-ray diffraction data for 1–4 were collected at 298(2) K on a Siemens
˚
Smart/CCD area-detector diffractometer with Mo-Ka radiation (ꢀ ¼ 0.71073 A) by
using an !–2ꢁ scan mode. Data collection and reduction were performed using SMART
and SAINT [22]. The structures were solved by direct methods, and the non-hydrogen
2
atoms were subjected to anisotropic refinement by full-matrix least-squares on F using
the SHELXTL package [23]. Hydrogen atoms were generated geometrically and
included in structure factor calculations.
3
3
. Results and discussion
.1. Preparation and general characterization
Most organically templated halometallates reported previously were prepared by
conventional solution approach, thus all of the title compounds were prepared by a
solution method. The four compounds were prepared with the same ratio of the
reactants (1 : 1) except 1 derived from L1. For the tin compounds, tin is þ4 although the
original material was SnCl ꢀ 2H O, similar to published results [19, 24]. Here the SnCl
2
2
2
may be oxidized by oxygen in the air. All of the compounds were isolated as colorless
crystals in yields higher than 60%. These compounds are not soluble in almost all
common solvents. The ability of metal chloride complexes to act as hydrogen-
bond acceptors has been noted in our database work [19] and previous examples (see,
e.g. [25]).

N-Containing aromatic bases and chlorometallates
1941
ꢂ1
IR spectra show strong vibrations at 3208–3370 cm , assignable to NH and NH of
2
ꢂ1
the cations. The bands for lattice water molecules are at 3508–3566 cm . Bands at 1610
ꢂ1
and 1450 cm
can be assigned to C¼C and C¼N stretches of the pyridyl,
naphthyridinyl, imidazolyl or aromatic rings. Compositions were determined by
elemental analysis (C, H, and N), and their structures were fully characterized by X-ray
diffraction analysis. Hydrogen atoms connected to O or N were placed in calculated
positions, which also indirectly confirms protonation of the N-containing bases. For
compounds with L2 and L3, the least basic nitrogen atoms are not protonated. The
crystallographic data and refinement details are summarized in table 1 and selected
bond distances and angles are listed in table 2; some important hydrogen bonds are
listed in table 3.
3
.2. Thermal properties
ꢁ
ꢁ
The TGA studies show that water in 1 are removed between 72.2 C and 76.6 C
(Observ. 5.34%, Calcd 5.49%). There is a sharp weight loss from 249.4 C to 278.2 C
for decomposition of the two cations (Observ. 43.81%, Calcd 43.92%). For 2, the first
ꢁ ꢁ
ꢁ
weight loss of 5.59% (Calcd 5.64%) corresponds to loss of water at 68.1–71.9 C; the
ꢁ
second weight loss of 54.42% (Calcd 54.48%) at 298–336 C results from loss of both
þ
ꢁ
(
HL2) . TGA studies show that 3 is stable below 300 C, with weight loss of 46.41%
2
Calcd 46.49%) corresponding to loss of two (H L2) at 354–384 C. For 4, the free
þ
ꢁ
(
water molecules are released from 71.4 to 76.6 C (Observ. 6.12%, Calcd 6.19%) and
2
decomposition of (H L3) begins at 338 C and ends at 362 C (Observ. 36.66%, Calcd
2
ꢁ
þ
ꢁ
ꢁ
2
3
6.79%).
3
3
.3. Structural descriptions
.3.1. Crystal structure of [(HL1) SnCl ] 2H O (1). Complex 1 was prepared by
6 2
.
2
reacting 2 mol of 2-methylquinoline (L1) with 1 mol of tin(II) chloride dihydrate in
water in the presence of hydrochloric acid. Two water molecules are involved in the
lattice as determined by elemental analysis. Different from its unsolvated compound
which crystallizes in the monoclinic space group C2/c with unit cell content of four
formula units [26], 1 crystallizes in the monoclinic space group P2(1)/c with unit cell
content of two formula units. The asymmetric unit of 1 consists of one 2-methylqui-
2ꢂ
nolium cation, a half of SnCl6 , and one free water molecule (figure 1). The geometry of
the cyclic component HL1 is generally similar to that of the parent in the corresponding
unsolvated compound [26]. Tin is coordinated in a distorted octahedron, with two
groups of three chlorides related by inversion symmetry. The Sn–Cl bonds were
˚
2
.4177(13)–2.4403(12) A. The Cl–Sn–Cl angles between neighboring chlorides deviate
ꢁ
ꢁ
slightly from 90 and Cl–Sn–Cl angles are exactly 180 between two trans chlorides as
required by symmetry. These geometric parameters are similar to previously published
results [19].
2ꢂ
The SnCl were connected by free water molecules through O–Hꢀ ꢀ ꢀCl hydrogen
6
bonds with O–Cl distances of 3.277(4)–3.409(3) A to form a 1-D chain running along
˚
˚
the a-axis. In the anion chain adjacent Sn–Sn separation is 7.438 A. Here water
molecules as donors form three O–Hꢀ ꢀ ꢀCl hydrogen bonds in tridentate bridge fashion,

1
942
S. Jin and D. Wang

N-Containing aromatic bases and chlorometallates
1943
˚
Table 2. Selected bond lengths (A) and angles ( ) for 1–4.
ꢁ
1
Sn(1)–Cl(3)
Sn(1)–Cl(2)
Cl(3)#1–Sn(1)–Cl(1)
Cl(3)–Sn(1)–Cl(2)
Cl(1)–Sn(1)–Cl(2)
Cl(3)–Sn(1)–Cl(2)#1
Cl(1)#1–Sn(1)–Cl(2)#1
2.4177(13)
2.4403(12)
90.16(5)
89.51(4)
90.00(4)
Sn(1)–Cl(1)
2.4395(12)
89.84(5)
90.16(5)
90.49(4)
90.00(4)
89.51(4)
Cl(3)–Sn(1)–Cl(1)
Cl(3)–Sn(1)–Cl(1)#1
Cl(3)#1–Sn(1)–Cl(2)
Cl(1)#1–Sn(1)–Cl(2)
Cl(3)#1–Sn(1)–Cl(2)#1
90.49(4)
90.00(4)
2
Cd(1)–Cl(3)
Cd(1)–Cl(4)
Cl(3)–Cd(1)–Cl(2)
Cl(2)–Cd(1)–Cl(4)
Cl(2)–Cd(1)–Cl(1)
2.4396(13)
2.4450(13)
107.48(5)
114.40(6)
107.33(5)
Cd(1)–Cl(2)
Cd(1)–Cl(1)
Cl(3)–Cd(1)–Cl(4)
Cl(3)–Cd(1)–Cl(1)
Cl(4)–Cd(1)–Cl(1)
2.4423(13)
2.4531(13)
111.67(5)
107.49(5)
108.17(5)
3
Sn(1)–Cl(3)
Sn(1)–Cl(2)
Cl(3)#1–Sn(1)–Cl(1)
Cl(1)–Sn(1)–Cl(1)#1
Cl(3)–Sn(1)–Cl(2)
Cl(1)–Sn(1)–Cl(2)#1
2.4196(9)
2.4426(8)
89.47(3)
179.25(5)
89.79(3)
91.02(3)
Sn(1)–Cl(1)
2.4247(8)
93.71(5)
91.04(3)
175.95(3)
88.44(3)
86.78(4)
Cl(3)#1–Sn(1)–Cl(3)
Cl(3)–Sn(1)–Cl(1)
Cl(3)#1–Sn(1)–Cl(2)
Cl(1)–Sn(1)–Cl(2)
Cl(2)–Sn(1)–Cl(2)#1
4
Sn(1)–Cl(3)
Sn(1)–Cl(1)
N(1)–N(1)#2
N(2)–C(5)
N(3)–C(3)
Cl(3)–Sn(1)–Cl(2)#1
Cl(3)–Sn(1)–Cl(1)#1
Cl(3)–Sn(1)–Cl(1)
2.4195(9)
2.4568(8)
1.338(6)
1.386(5)
1.303(5)
89.17(3)
90.49(3)
89.51(3)
Sn(1)–Cl(2)#1
N(1)–C(1)
N(2)–C(3)
N(2)–C(1)
N(3)–C(4)
Cl(3)–Sn(1)–Cl(2)
Cl(2)–Sn(1)–Cl(1)#1
Cl(2)–Sn(1)–Cl(1)
2.4256(9)
1.318(4)
1.344(4)
1.429(4)
1.377(5)
90.83(3)
89.92(3)
90.08(3)
Symmetry transformations used to generate equivalent atoms for 1: #1: ꢂx þ 1, ꢂy þ 1, ꢂz þ 2; for 3: #1: ꢂx,
y, ꢂz þ 1/2; for 4: #1: ꢂx þ 1/2, ꢂy þ 3/2, ꢂz; #2: ꢂx, y, ꢂz þ 3/2.
ꢂ
i.e., one hydrogen forms two hydrogen bonds in bifurcate fashion with two Cl coming
ꢂ
from the same anion, while another hydrogen forms only one hydrogen bond with Cl
2ꢂ
2ꢂ
of the other adjacent SnCl6 . Two water molecules and two SnCl6 form a
1
2-membered ring through the O–Hꢀ ꢀ ꢀCl contacts; in this case the corresponding
anions and the water molecules in the 12-membered ring are related by inversion
symmetry with the inversion centre lying at the midpoint of the two oxygen atoms of the
two water molecules. The cations bond to water in the anion chain through N–Hꢀ ꢀ ꢀO
þ
˚
hydrogen bonds between NH and water with N–O distance of 2.731(5) A, smaller than
the sum of the van der Waals contact [27]. Two cations bonded to the same
1
2-membered ring are also inversionally arranged; cations at the same side of the same
anion chain were parallel, while those cations at different sides of the anion chain were
antiparallely arranged. In the structure of 1 there are two independent parallel chains
without interactions between the two chains (figure 2). The second chain is located
above the first chain when viewed from the c-axis, but the second chain slipped ca half
of the length of the b-axis from the first chain along the b-axis. Cations on the same side
of the same chain were parallel. The cations in these two chains are not parallel to each
ꢁ
other, forming an angle (ca 60 ) with each other.

1
944
S. Jin and D. Wang
Table 3. Hydrogen-bond geometries for 1–4 (A, ).
˚
ꢁ
D–Hꢀ ꢀ ꢀA
d(Dꢀ ꢀ ꢀA)
1
O(1)–H(1D)ꢀ ꢀ ꢀCl(2)#2
O(1)–H(1D)ꢀ ꢀ ꢀCl(3)#3
O(1)–H(1C)ꢀ ꢀ ꢀCl(1)#4
N(1)–H(1)ꢀ ꢀ ꢀO(1)#5
3.375(3)
3.277(4)
3.409(3)
2.731(5)
2
O(2)–H(2D)ꢀ ꢀ ꢀCl(2)#1
O(2)–H(2C)ꢀ ꢀ ꢀCl(1)#2
O(1)–H(1D)ꢀ ꢀ ꢀCl(4)#3
O(1)–H(1C)ꢀ ꢀ ꢀCl(3)#4
N(6)–H(6B)ꢀ ꢀ ꢀCl(1)#5
N(6)–H(6A)ꢀ ꢀ ꢀN(1)#6
N(5)–H(5)ꢀ ꢀ ꢀO(1)
3.274(4)
3.213(4)
3.209(4)
3.290(4)
3.415(4)
3.166(5)
2.789(5)
3.098(6)
3.359(5)
3.244(6)
2.835(5)
N(3)–H(3B)ꢀ ꢀ ꢀO(1)#7
N(3)–H(3B)ꢀ ꢀ ꢀCl(3)#8
N(3)–H(3A)ꢀ ꢀ ꢀN(4)#7
N(2)–H(2)ꢀ ꢀ ꢀO(2)
3
N(3)–H(3B)ꢀ ꢀ ꢀCl(4)#2
N(3)–H(3 A)ꢀ ꢀ ꢀCl(2)
N(2)–H(2)ꢀ ꢀ ꢀCl(4)#3
N(1)–H(1)ꢀ ꢀ ꢀCl(4)#3
3.287(3)
3.373(3)
2.963(3)
3.174(2)
4
O(1)–H(1D)ꢀ ꢀ ꢀCl(3)#3
O(1)–H(1C)ꢀ ꢀ ꢀN(1)#4
N(3)–H(3)ꢀ ꢀ ꢀO(1)#5
3.392(3)
2.995(4)
2.851(4)
Symmetry codes for 1: #2: x þ 1, ꢂy þ 3/2, z ꢂ 1/2; #3: ꢂx þ 2,
y þ 1/2, ꢂz þ 3/2; #4: ꢂx þ 1, y þ 1/2, ꢂz þ 3/2; #5: x ꢂ 1, y, z; for 2:
#
1: ꢂx, y ꢂ 1/2, ꢂz þ 1/2; #2: ꢂx þ 1, y ꢂ 1/2, ꢂz þ 1/2; #3: x,
ꢂy þ 3/2, z þ 1/2; #4: x þ 1, ꢂy þ 3/2, z þ 1/2; #5: ꢂx þ 1, ꢂy þ 1,
ꢂz þ 1; #6: x, ꢂy þ 1/2, z þ 1/2; #7: x, ꢂy þ 1/2, z ꢂ 1/2; #8: x þ 1,
y ꢂ 1, z; for 3: #2: ꢂx þ 1/2, ꢂy þ 1/2, ꢂz; #3: ꢂx þ 1/2, y þ 1/2,
ꢂz þ 1/2; for 4: #3: ꢂx þ 1/2, y ꢂ 1/2, ꢂz þ 1/2; #4: x, y ꢂ 1, z; #5:
x, ꢂy þ 1, z ꢂ 1/2.
Figure 1. Molecular structure of 1 showing the atomic-numbering scheme at 30% thermal ellipsoid
probability level.

N-Containing aromatic bases and chlorometallates
1945
Figure 2. Two independent parallel chains running along the a-axis.
Figure 3. Molecular structure of 2 showing the atomic-numbering scheme at 30% ellipsoid probability level.
3.3.2. Crystal
structure
of
[(HL2) (CdCl )]
2
.
2H O
2
(2). Compound
2,
4
[
are four formula units in its unit cell. X-ray diffraction analysis shows the complex
(HL2) (CdCl )] ꢀ 2H O, crystallizes in a monoclinic P2(1)/c space group, and there
2
4
2
2
composed of two monoprotonated L2 cations, one [CdCl4] and two free water
ꢂ
molecules (figure 3). In 2, the ring N adjacent to the methyl is protonated and the cation

1
946
S. Jin and D. Wang
þ
with the NH on the naphthyridine rings in 2 resembles 2-amino-4,6-dimethylpyr-
0
0
idinium cations [28]. Similar to the organic salt 2,2 -dimethyl-7,7 (methylenediimino)di-
1
,8-naphthyridin-1-ium bis(perchlorate) [29], the less basic ring N has been protonated.
The coordination geometry around Cd(II) is a distorted tetrahedron with four
˚
˚
chlorides. The Cd–Cl bond distances range from 2.4396(13) A to 2.4531(13) A,
consistent with other similar compounds in which the cadmium has tetrahedral
coordination [25]. Different from the coordination compound containing 2-amino-5,7-
dimethyl-1,8-naphthyridine [30], the NringCNring angles (N(1)–C(5)–N(2) and N(4)–
ꢁ
C(15)–N(5) in 2 are both 116.4(4) ), are larger than the corresponding angles (112.7(3)
ꢁ
and 112.6(3) ) in bis(2-amino-5,7-dimethyl-1,8-naphthyridine) dinitratocadmium. Thus
we deduce that bidentate chelating coordination to cadmium led to a larger contraction
ꢁ
(
the NringCNring angle should be ca 120 if there are no bonding interactions with the two
ring nitrogen atoms) in the NringCNring angle of the coordination compound containing
-amino-5,7-dimethyl-1,8-naphthyridine [30] compared with the hydrogen-bonding
interactions in 2. Coordinate bonds are stronger than hydrogen bonds in this case.
2
Two monoprotonated naphthyridine cations were connected through weak comple-
2
ꢂ
mentary hydrogen bonds, N–Hꢀ ꢀ ꢀN, to form dimers, the anions [CdCl ] bond to the
4
dimers through N–Hꢀ ꢀ ꢀCl hydrogen bonds between the amine and chlorides with
˚
Nꢀ ꢀ ꢀCl separation of 3.359(5) A. The dimers in the same plane were connected through
˚
5
structure when viewed down the a-axis. In the 2-D sheet there were also CH–Cl
–CH ꢀ ꢀ ꢀCl interaction in which the C–Cl distance is 3.756 A to form a 2-D sheet
3
2
ꢂ
˚
interactions between CH of the cation and [CdCl4] with C–Cl distance of 3.553 A.
The 2-D sheets were further linked through water molecules in which water acts as bis
hydrogen-bond donor to form hydrogen bonds with two [CdCl4] anions in a 3-D layer
structure (figure 4). The two free water molecules each form three hydrogen bonds, each
2
–
Figure 4. Packing diagram of 2 showing the 3-D layer structure.

N-Containing aromatic bases and chlorometallates
1947
hydrogen forms a O–Hꢀ ꢀ ꢀCl hydrogen bond with the anion, and each oxygen forms a
þ
N–Hꢀ ꢀ ꢀO hydrogen bond with the NH group with N–O distances ranging from
˚
.789(5) to 2.835(5) A.
2
˚
The N(5)–O(1) distance is 2.789(5) A, which is considerably less than the sum of the
˚
van der Waals radii for N and O (3.07 A) [27], so in the solid state, there are strong
þ
charge-assisted hydrogen bonds formed between the naphthyridinium NH and water.
In the other N–Hꢀ ꢀ ꢀO hydrogen bond between water and NH (N(3)–H(3B)ꢀ ꢀ ꢀO(1)#7,
2
˚
symmetry code #7: x, ꢂy þ 1/2, z ꢂ 1/2), the N(3)–O(1) distance is 3.098(6) A,
comparable to the sum of the van der Waals radii, indicating a neutral hydrogen
bond [27].
3
.3.3. Crystal structure of [(H L2) SnCl ] 2(Cl) (3). Complex 3 was prepared by
6
.
2
2
reacting 5,7-dimethyl-1,8-naphthyridine-2-amine (L2) with 1 equivalent of tin(II)
chloride dihydrate in water in the presence of hydrochloric acid. There were no water
molecules involved in the lattice as determined by elemental analysis. Different from 2,
both nitrogen atoms on the naphthyridine ring were protonated to form dications, the
first case where two ring nitrogen atoms of naphthyridine have been protonated.
Complex 3 crystallizes in the monoclinic space group C2/c with unit cell content of four
formula units; the asymmetric unit consists of one naphthyridinium dication, a half of
2
6
ꢂ
SnCl , and one free chloride (figure 5).
The Sn–Cl bonds were 2.4196(9)–2.4426(8) A, in the range of reported results
˚
˚ ˚ ˚
(
2.402(3)–2.483(3) A) [31]. The Sn(1)–Cl(3) (2.4196(9) A) and Sn(1)–Cl(1) (2.4247(8) A)
˚
bond distances are almost equal, while Sn(1)–Cl(2) (2.4426(8) A) is longer than other
Sn–Cl bonds, probably because Cl(2) forms more hydrogen bonds than the other
chlorides.
ꢁ
The Cl–Sn–Cl angles between two neighboring chlorides are close to 90 (Cl(1)–
ꢁ
ꢁ
ꢁ
Sn(1)–Cl(2) 88.44(3) ; Cl(3)–Sn(1)–Cl(1) 91.04(3) ; Cl(3)–Sn(1)–Cl(2) 89.79(3) ), indi-
cating Sn is in a slightly distorted octahedral environment.
Figure 5. Molecular structure of 3 showing the atomic-numbering scheme at 30% thermal ellipsoid
probability level.

1
948
S. Jin and D. Wang
Figure 6. 3-D layer network formed via Cl–ꢆ, CH–Cl, and NHamine–Cl interactions.
ꢂ
The naphthyridines were connected through the free Cl which formed hydrogen
þ
bonds simultaneously with amine of one naphthyridine and two NH groups of the
other naphthyridine to form a 1-D zigzag chain along the c-axis. In the chain there also
˚
exists CH–Cl interaction (with C–Cl distance of 3.577 A) between free chloride and
6
distance of 3.472 A and 3.6 A) and NHamine–Cl hydrogen bonds to form a 2-D grid
-CH of 1,8-naphthyridine. Adjacent chains were combined through CH–Cl (with C–Cl
˚
˚
structure. The 2-D grids were further joined by Cl–ꢆ (with separation between the free
ꢂ
˚
˚
Cl and the naphthyridine ring of 3.368 A), CH–Cl (with C–Cl distance of 3.472 A and
˚
.6 A), and NH
˚
–Cl (with N–Cl distance of 3.373 A) to form a 3-D layer network,
amine
3
figure 6. Obviously, the 3-D structure is stabilized by these hydrogen bonds.
3
.3.4. Crystal structure of [(H L3)SnCl ] 2H O (4). Complex 4 was also prepared by
6 2
.
2
reacting 3,6-bis(imidazol-1-yl)pyridazine (L3) with tin(II) chloride dihydrate in water in
the presence of conc. hydrochloric acid. The compound was isolated in high yield as
colorless block crystals, crystallizing in a monoclinic space group C2/c with unit cell of
four formula units. The molecular structure is shown in figure 7. In the asymmetric unit
of 4 there are half of the cations and the anion accompanied with one water molecule.
Two nitrogen atoms of imidazole but no nitrogen atoms of pyridazine ring were
protonated to yield the dication which conforms with literature results [32, 33]. In 4, the
tin is coordinated in a distorted octahedral geometry by six chlorides also.
Imidazole rings and pyridazine rings are both planar with largest deviation from the
˚
plane of 0.0091 A. In the same cation the dihedral angle between the two imidazole
ꢁ
rings is 65.1 , and the dihedral angle between the pyridazine and the imidazole rings is
32.6 , different from the literature values (70.8 , 45.9 , and 24.8 ) [33]. All of the bond
lengths are in the normal range, Sn–Cl are 2.4195(9) – 2.4568(8) A. The cis Cl–Sn–Cl
ꢁ ꢁ ꢁ ꢁ
˚
ꢁ
ꢁ
angles are close to 90 and the trans Cl–Sn–Cl angle is 180 , which fits well with the
crystallographic symmetry of the compound.
The cations and the anions are arranged alternately along the a-axis. The anions and
cations are joined by six Cl–ꢆ interactions of which four arise from the pyridazine ring
ꢂ
˚
and Cl with Cl–Cg distance of 3.442–3.390 A, the other two arise from the imidazole

N-Containing aromatic bases and chlorometallates
1949
Figure 7. Molecular structure of 4 showing the atomic-numbering scheme at 30% ellipsoid probability level.
ꢂ
˚
ring and Cl with Cl–Cg distance of 3.316 A to form a 1-D chain along the a-axis. Here
the Cl–ꢆ interactions of imidazole are somewhat stronger than that produced by
pyridazine. In the chain, adjacent cations were antiparallel, and the third cation and the
first cation were parallel to each other, as was the fourth cation and the second cation.
˚
In the same chain, the Sn–Sn distance is 9.440 A; Sn–Sn distances between adjacent
˚
˚
chains are 10.096 A and 11.073 A, respectively. Such 1-D parallel chains were held
þ
together by water molecules through one N–Hꢀ ꢀ ꢀO hydrogen bond between NH and
˚
water with N–O distance of 2.851(4) A, one O–Hꢀ ꢀ ꢀCl interaction between the anion
˚
and water with O–Cl distance of 3.393 A, and one CH–O interaction arising from
˚
N–CH–N of L3 and water with C–O distance of 3.100 A to form a 2-D sheet extending
along the ac plane (figure 8). Such sheets were further stacked along the b-axis through
˚
O–Hꢀ ꢀ ꢀN contacts between the pyridazine ring and water with O–N distance of 2.995 A,
and CH–Cl interactions between the cation and the anion with C–Cl distances of
˚
3
.624–3.737 A. Under these interactions 4 displayed a 3-D network structure.
4
. Conclusions
We synthesized four new inorganic–organic hybrid solids by solution reaction of SnCl2/
CdCl with N-containing aromatic Brønsted bases in strongly acidic conditions. The Cd
2
in 2 is tetrahedral, while Sn in 1, 3, and 4 are octahedral. For L2 and L3, the least basic
nitrogen atoms are not protonated.
These compounds display two independent parallel chain structures, 3-D layer
structure, and 3-D network structure with N–Hꢀ ꢀ ꢀCl, N–Hꢀ ꢀ ꢀO, O–Hꢀ ꢀ ꢀN, and
O–Hꢀ ꢀ ꢀCl interactions as well as Coulombic interactions. Other than classical
hydrogen-bonding interactions, secondary propagating interactions such as CH–Cl,
Cl–ꢆ, and CH–O also play important roles in structure extension and stabilization.
Cadmium chloride and SnCl2 are effective hydrogen-bond acceptors, such that
tetrachlorocadmate and hexachlorostannate may be exploited to prepare metal-
2
þ
2þ
containing hydrogen-bonded polymers composed of ½HLꢅ2 or [H L]
salts of
perchlorometallates. Choice of anions without hydrogen-bond donors and cations
with strong hydrogen-bond donors is a successful strategy.
2

1
950
S. Jin and D. Wang
dF oi gwu nr et h8 e. b -2 a- xD is .s heet structure of 4 formed through N–Hꢀ ꢀ ꢀO, O–Hꢀ ꢀ ꢀCl, and CH–O interaction as viewed
The structural motifs of these inorganic–organic hybrid complexes depend on the
shape, size, and symmetry of the organic cations. Inorganic–organic hybrid compounds
can be expected by variation of the organic cations. All of the compounds show high
thermal stabilities.
Supplementary material
Crystallographic data for the structural analysis have been deposited with the
Cambridge Crystallographic Data Centre, CCDC Nos 791896 for 1, 739933 for 2,
7
46313 for 3, and 791895 for 4. Copies of this information may be obtained free of
charge via Fax: þ44(1223)336-033 or E-mail: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk
Acknowledgments
We gratefully acknowledge the Education Office Foundation of Zhejiang Province
(
(
project No. Y201017321) and the Zhejiang A & F University Science Foundation
project No. 2009FK63) for the financial support.

N-Containing aromatic bases and chlorometallates
1951
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