Synthesis and crystal structure of bis (tetrabutylammonium)(4,4′- azodi(phenylcyanamide)) salt ? [(n-Bu)4N] 2[azodicyd2-] ? H2O

Article abstract of DOI:10.1007/s10870-007-9313-7

The chemical preparation and crystal structure for a 4,4′- azodi(phenylcyanamide) salt) in the solid state are reported. This compound crystallizes in the triclinic space group P with the following unit cell parameters: a = 9.759(3) A, b = 11.237(4) A, c = 11.919(4) A, α = 95.54(3)°, β = 98.50(3)°, γ = 109.39(2)°, Z = 1 and V = 1204.4(7) A³. The 4,4′-azodi(phenylcyanamide) dianion, azodicyd^2-, is approximately planar, with the cyanamide groups (-N=C=N) in an anti conformation relative to each other and the azo group (-N=N-) adopting the more thermodynamically stable trans conformation. The crystal X-ray analysis shows that there are one azo molecule cation, two tetrabutylammonium cations and one water molecule in unit cell. Intermolecular O-H???N hydrogen bonds may be effective in the stabilization of the crystal structure of this compound and to form linear chain structure in the packing. Synthesis and crystal structure of Bis (Tetrabutylammonium)(4, 4′-Azodi(phenylcyanamide)) salt . [(n-Bu)4N]2[Azodicyd^2-] ? H₂O[Figure not available: see fulltext.] Davar M. Boghaei ¹, Fatemeh Behzadian-Asl ¹ and Hamid Reza Khavasi ^{2 1} Department of Chemistry, Sharif University of Technology, P.O. Box 11155-9616, Tehran, Iran ² Department of Chemistry, Shahid Beheshti University, Evin, Tehran 1983963113, Iran

Full text of DOI:10.1007/s10870-007-9313-7

J Chem Crystallogr (2008) 38:311–314
DOI 10.1007/s10870-007-9313-7
ORIGINAL PAPER
Synthesis and Crystal Structure of Bis (Tetrabutylammonium)
(4,40-Azodi(phenylcyanamide)) Salt ꢀ [(n-Bu)4N]2
[Azodicyd2-] ꢀ H2O
Davar M. Boghaei Æ Fatemeh Behzadian-Asl Æ
Hamid Reza Khavasi
Received: 12 September 2006 / Accepted: 19 November 2007 / Published online: 1 December 2007
Ó Springer Science+Business Media, LLC 2007
Abstract The chemical preparation and crystal structure
for a 4,40-azodi(phenylcyanamide) salt) in the solid state
Introduction
are reported. This compound crystallizes in the triclinic
Recently, phenylcyanamide ligand families are of consid-
erable interest due to their importance as materials that
possess useful optical, magnetic, and/or electronic proper-
ties. The phenyl cyanamide ligands are expected to be as
potentially rich as that of the pseudohalids (for example,
azide or thiocyanate). The attachment of a phenyl ring to
the cyanamide group adds an extra dimension not present
in azide or thiocyanate ligands [1–5]. The cyanamide group
is a three-atom p-system in which the amine non-bonding
electrons can delocalize into the nitrile p-bonds. Accord-
ingly, the cyanamide group is expected to be a poorer p-
acceptor but better donor than analogous nitrile ligand. For
this reason, cyanamides are expected to be less sensitive to
base hydrolysis. The phenylcyanamide ligand families
have been used in architecture of hybrid polymeric mate-
rials and mixed-valance complexes because of its abilities
in forming bridge via cyanamide groups [6, 7]. Here, we
report the synthesis and X-ray determination of a 4,40-
azodiphenylcyanamide salt (azodicyd2-).
ꢁ
space group P with the following unit cell parameters: a =
1
˚
˚
˚
9.759(3) A, b = 11.237(4) A, c = 11.919(4) A, a =
95.54(3)°, b = 98.50(3)°, c = 109.39(2)°, Z = 1 and V
3
0
˚
= 1204.4(7) A . The 4,4 -azodi(phenylcyanamide) dianion,
azodicyd2-, is approximately planar, with the cyanamide
groups (–N=C=N) in an anti conformation relative to each
other and the azo group (–N=N–) adopting the more ther-
modynamically stable trans conformation. The crystal X-
ray analysis shows that there are one azo molecule cation,
two tetrabutylammonium cations and one water molecule
in unit cell. Intermolecular O–HꢀꢀꢀN hydrogen bonds may
be effective in the stabilization of the crystal structure of
this compound and to form linear chain structure in the
packing.
Keywords 4,40-Azodi(phenylcyanamide) ꢀ Cyanamide
groups ꢀ Hydrogen bond ꢀ Crystal structure
Experimental
All chemicals were of analytical reagent grade and were
used directly without further purification. Elemental anal-
ysis (C, H, N) was performed with a Perkin-Elmer 2400
Electronic supplementary material The online version of this
article (doi:10.1007/s10870-007-9313-7) contains supplementary
material, which is available to authorized users.
CHN/O elemental analyzer. IR spectra (4000–400 cm-1
)
D. M. Boghaei (&) ꢀ F. Behzadian-Asl
Department of Chemistry, Sharif University of Technology,
P.O. Box 11155-3516, Tehran, Iran
were measured on a FT-IR JASCO 460 spectrophotometer
with KBr pellets. Electronic spectra were recorded using a
1
CARY 100 Bio VARIAN UV–Vis spectrophotometer. H
e-mail: dboghaei@sharif.edu
NMR spectrum was recorded on a Bruker FT-NMR 500
(500 MHz) Ultra Shield spectrometer at ambient temper-
ature in DMSO-d6.
H. R. Khavasi
Department of Chemistry, Shahid Beheshti University, Evin,
Tehran 1983963113, Iran
123

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J Chem Crystallogr (2008) 38:311–314
solved by direct method [9] and refined on F2 by full-
matrix least-square using the X-STEP32 program package
[10] giving a final R1 = 0.0593, wR2 = 0.1444. The largest
peak and hole on the final difference-Fourier map were
Synthesis of [(n-Bu)4N]2[azodicyd] ꢀ 2H2O
Ammonium thiocyanate (1.5 g, 20 mmol) was dissolved in
20 mL of acetone and brought to a boil. To this was added
dropwise a solution of benzoyl chloride (2.8 g, 20 mmol)
in 20 mL of acetone, and the mixture was refluxed for an
additional 15 min. 4,40-Azodianiline (2.1 g, 9.9 mmol) was
dissolved in 150 mL of boiling acetone and then slowly
added to the refluxing mixture above. The mixture was
refluxed for 1 h and then poured into a beaker containing
800 mL of water. The brown benzoyl thiourea precipitate
was removed by suction filtration and dissolved in 300 mL
of boiling 2 M NaOH. The resulting deep red solution was
boiled for 5 min and then cooled to 60 °C. Lead acetate
(7.5 g, 20 mmol) was dissolved in 20 mL of water and
added to the thiourea solution. The temperature was
maintained at 60 °C for 15 min, forming a black PbS
precipitate, and the mixture was then filtered by suction
into an ice-cooled flask. The filtrate was acidified to pH 5
with the addition of 25 g of glacial acetic acid, and a green
precipitate were removed by suction filtration. Recrystal-
lization from 700 mL of boiling acetone afforded a
greenish gold solid. (This greenish gold solid was az-
odicydH2). A (0.098 g, 0.37 mmol) azodicydH2 was
dissolved in 100 mL of boiling 2/1 acetone/water solution
and was added excess triethylamine. To this was added a
solution of [N(n-But)4]Cl (0.194 g, 0.80 mmol) in 20 mL
of water, and the mixture was stirred and heated for
15 min. The red precipitate was collected and washed with
30 mL of water. Single crystal suitable for X-ray diffrac-
tion was grown by slow diffusion of diethyl ether in to an
acetone solution at 298 K. Anal. Calcd for C46H82N8O1:
C, 72.44; H, 10.76; N, 14.70%. Found: C, 72.40; H, 10.69;
N, 14.75%. IR (KBr):3058 (m), 3408 (m), 2960 (m), 2872
(m), 2093 (s), 1578 (s), 1543 (m), 1491 (s), 1341 (s), 1235
0.245 and -0.256 e/A-3, respectively. Crystal data and
˚
structure refinement parameter are listed in Table 1.
Selected bond lengths and angles are given in Table 2.
Result and Discussion
An ORTEP [11] drawing and a packing diagram of this
compound is shown in Figs. 1 and 2, respectively. The
anionic cyanamide groups of azodicyd2- are approximately
Table 1 Crystallographic data and structure Refinement for [(n-
Bu)4N]2[azodicyd] ꢀ H2O
Molecular formula
Molecular weight
Crystal size (mm)
Crystal color
C46H82N8O1
781.22
0.45 9 0.15 9 0.10
Red
Crystal system
Tꢁriclinic
Space group
P
1
Unit cell dimensions
˚
a (A)
9.759(3)
˚
b (A)
11.237(4)
˚
c (A)
11.919(4)
a (°)
b (°)
c (°)
95.54(3)
98.50(3)
109.39(2)
3
˚
V (A )
1204.4(7)
Z
1
Dc (g/cm3)
1.077
F (000)
Goodness of fit on F2
Absorption coefficient (mm-1
432
1.081
(m), 1134 (s), 876 (m), 842 (m), 740 (m) cm-1. H NMR
1
)
0.067
(500 MHz): 7.42 (4H, d), 6.62 (4H, d), 3.13(16H, t), 1.54
(16H, q), 1.30 (16H, m), 0.9 (24H, t) ppm.
Absorption correction Tmax and Tmin
0.995 and 0.985
0.245 and -0.256
4229/0/397
-3
)
˚
Largest diff. Peak and hole (e A
Data/restraints/parameters
Final R indices [I [ 2r(I)]
R indices (all data)
R1 = 0.0593, wR2 = 0.1444
R1 = 0.0807, wR2 = 0.1570
X-ray Crystallography
A red single crystal with dimension of 0.45 mm 9 0.15
mm 9 0.1 mm was chosen for X-ray diffraction study.
Diffraction measurements were carried out on a STOE
IPDS II two-circle diffractometer using graphite-mono-
˚
Table 2 Selected bond lengths (A) and bond angles (°) for [(n-
Bu)4N]2[azodicyd] ꢀ 2H2O
C(1)–N(1)
C(1)–N(2)
C(2)–N(2)
C(5)–N(3)
N(3)–N(3)#1
1.169(3)
1.288(3)
1.389(3)
1.430(3)
1.247(4)
N(1)–C(1)–N(2)
N(2)–C(2)–C(7)
N(2)–C(2)–C(3)
C(4)–C(5)–N(3)
C(6)–C(5)–N(3)
172.6(2)
118.4(2)
124.5(2)
115.9(2)
125.7(2)
˚
chromated Mo-Ka (k = 0.71073 A) radiation at 173 K.
Cell parameters were determined by the least-squares cal-
culation with h angle ranging from 1.75 to 25.60°. A
numerical absorption correction was applied to the data
with the help of the programs X-RED and X-SHAPE [8]. A
total of 4229 independent reflections were collected, giving
397 observed reflections with I [ 2r(I). The structure was
Symmetry transformations used to generate equivalent atoms: #1
-x + 1, -y + 2, -z + 2
123

J Chem Crystallogr (2008) 38:311–314
313
significant double bond character. This indicates that the
bond lengths of the cyanamide group are not simply the
average of resonance forms of ðꢁN¼C¼Nꢁ ꢀ ꢁNꢁ
ꢁCꢂNÞ and this suggest that carbon in cyanamide pos-
sesses hypervalent character. In contrast, the crystal
structure of [{Ru(terpyridine)(bpy)}2(l-azodicyd)][PF6]2
showed that its azodicydo terminal nitrogen to carbon bond
length is decreased (1.162(7)) but the carbon to amide
nitrogen bond length is increased (1.299(8)) [12]. The 1,4-
dicyanamidebenzene and its substituted derivatives possess
similar cyanamide group bond lengths and angles[15–17].
The cyanamide planes formed by N1–C1–N2 are tilted
by only 3.8° with respect to the plane of phenyl rings. The
azodicyd2- is approximately planar, with the cyanamide
groups in an anti conformation relative to each other and
the azo group adopting the more thermodynamically stable
trans conformation. The planar geometry of the dianion
ligand is suggested to allow for a more effective p-delo-
calization of the cyanamide groups with phenyl and azo
groups. This extensive p conjugation between the cyana-
mide and azo groups and phenyl ring provides an
energetically favorable means by which a metal ion can
couple into a conjugated organic p system. In this atomic
arrangement, there are two tetrabutylammonium cations
per one azodicyd2- anion to ensure the electric neutrality
of the total compound and one water molecule in the unit
cell. The azodicyd2- anion in the solid state possesses
an inversion center, it seems likely that the complex in
solution will be able to access a range of possible confor-
mations of lower symmetry, and this will have relevance to
the spectroscopic analysis to follow. As Fig. 2 reveals,
there is some intermolecular O–HꢀꢀꢀN [H1AꢀꢀꢀN1i
Fig. 1 ORTEP diagram of the [(n-Bu)4N]2[azodicyd] showing 30%
probability ellipsoids [10]. Hydrogen atoms and some atom number-
ing are omitted for clarity.
i
i
˚
= 2.42(6), O1ꢀꢀꢀN1 = 2.974(4) A and O1–H1AꢀꢀꢀN10 =
ii
ii
˚
115(4)° and H1BꢀꢀꢀN1 = 1.97(9), O1ꢀꢀꢀN1 = 2.858(4) A
and O1–H1BꢀꢀꢀN1ii = 162(5)°, symmetry codes: (i) -X,
1-Y, 2-Z; (ii) -1+X, Y, -1+Z] hydrogen bonds. Con-
sequently, hydrogen bonds stabilize a one-dimensional
network formed with the anion parts that the cations will be
laid between these chains (Fig. 3). The presence of
hydrogen bonding might be expected to significantly affect
other lattice interactions. The O–H groups of water mole-
cule act as hydrogen donors and nitrogen atoms of the
azodicyd2- ligand act as acceptors. The potential hydrogen
bonds between O–HꢀꢀꢀN connect azo molecules to form
Fig. 2 Crystal packing diagram for this compound and showing
hydrogen bonding
linear with the NCN angle of 172.6(2)° as is seen in the
coordination to the metal atoms through its terminal nitro-
gen sites. The study shows that the size of this angle does
not change significantly when it is coordinated to the metal
atom, such as, for example in some of the Ru- azodicyd2-
complexes [12]. In the structure consist of centrosymetric
dinuclear units linked by double end to end phenylcya-
namido bridges, bond angle range NCN are between
175.5(3)° and 177.0(8)° [13, 14]. The terminal nitrogen to
carbon bond length (N1-C1) is 1.169(3). This bond length
shows significant triple bond character. The carbon to
amide nitrogen bond length (C1–N2) is 1.288(3) showing
Fig. 3 Fragment of 1D network of hydrogen bonding found in this
compound
123

314
J Chem Crystallogr (2008) 38:311–314
¨
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linear chain structure in crystal structure. Hydrogen bonds
seem to de effective in stabilization of the crystal structure.
Electronic spectrum of this compound was taken in
different solvents (different dielectric). Electronic spectra
of the compound in acetonitrile shows two absorption
bands in the UV region and one absorption band in the
visible region. The absorption bands centered at 264,
336 nm are assigned to ligand-centered p ? p* transitions.
The intense absorption bands centered at approximately
491 nm is assigned to n ? p* since this band is shifted
toward shorter wavelengths (blue shift) in high dielectric
solvents, while a red shift was observed for the p ? p*
transitions in high dielectric solvents [18].
ˇ
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Crystallographic data for the structure reported in this
paper have been deposited with the Cambrige Crystallo-
graphic Data Center as supplementary publication no.
CCDC 605445. Copies of the data can be obtained free of
charge on application to CCDC, 12 Union Road, Cam-
bridge CB2 1EZ, UK (Fax: (+44) 1223-336033; e-mail:
deposit@ccdc.cam.ac.uk; url: http://www.ccdc.cam.ac.uk).
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(1993) Acta Crystallogr C39:1543
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lege, Mexico, pp 118–119
Acknowledgements We are grateful to the Sharif University of
Technology for financial support.
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