The first polymeric pentacoordinate zinc(ii) azoimidazole complex

Article abstract of DOI:10.1016/j.mencom.2011.03.009

Coupling of 4,5-dichloro-2-phenyldiazenyl-1H-imidazole with zinc acetate gives rise to polymeric pentacoordinate Znii complex, whose structure was determined by X-ray diffraction study.

Full text of DOI:10.1016/j.mencom.2011.03.009

Mendeleev
Communications
Mendeleev Commun., 2011, 21, 87–88
The first polymeric pentacoordinate zinc(ii) azoimidazole complex
Anatolii S. Burlov,a Alla S. Antsyshkina,b Georgii G. Sadikov,b Alexander A. Zubenko,c
Sergei A. Mashchenko,a Igor S. Vasilchenko,*a Vladimir S. Sergienko,b
Alexander D. Garnovskiia and Vladimir I. Minkina,d
a Institute of Physical and Organic Chemistry, Southern Federal University, 344090 Rostov-on-Don,
Russian Federation. Fax: +7 863 243 4667; e-mail: vas@ipoc.rsu.ru
b N. S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, 119991 Moscow,
Russian Federation. Fax: +7 495 954 1279; e-mail: common@ionchran.msk.ru
c Southern Caucasian Regional Institute of Veterinary, 346400 Novocherkassk, Russian Federation
d Southern Scientific Center of the Russian Academy of Sciences, 344090 Rostov-on-Don, Russian Federation.
E-mail: minkin@ipoc.rsu.ru
DOI: 10.1016/j.mencom.2011.03.009
Coupling of 4,5-dichloro-2-phenyldiazenyl-1H-imidazole with zinc acetate gives rise to polymeric pentacoordinate Znii complex,
whose structure was determined by X-ray diffraction study.
Metal complexes with aromatic and heterocyclic azo ligands are
amongst the most important objects of modern coordination
chemistry1–3 since they are prospective for molecular electronics
and photonics.1–8 The previously obtained metal complexes of azo
ligands, e.g., Zn complexes,9–12 are monomeric in solution while
in crystal their molecules form associates stabilized by secondary
bonds. The majority of described polymeric metallocomplexes
are obtained based on functionalized aromatic ligands.13
Here we report on the first case of the formation of a polymeric
pentacoordinate Znii azoimidazole complex prepared by coupling
of 4,5-dichloro-2-phenyldiazenyl-1H-imidazole with zinc acetate
(Scheme 1). Synthesis of 4,5-dichloro-2-phenyldiazenyl-1H-
imidazole 1 has been performed by azo-coupling of 4,5-dichloro-
imidazole with phenyldiazonium salt.† Zinc complex 2 has been
obtained by refluxing methanol solution of the reactants for 2 h.‡
The structure of complex 2 was studied by X-ray diffraction
method (Figure 1).§ An interesting feature of this complex con-
taining two five-membered bis-chelate units is an additional short
axial Zn–N bond that coordinates the ZnN4 core to imidazole
rings of the adjacent bis-chelate molecules to form slightly distorted
trigonal bipyramidal ZnN5 moieties with three shorter equatorial
Zn–N bonds with N(3), N(7) and N(8A) atoms and elongated
Cl
Cl
N
N
Zn(OAc)2
N
N
Ph
H
1
Zn
Cl
Cl
N
Zn
N
N
2
Ph
Cl
Cl
N
N
Ph
Ph
N
N
N
N
N
Zn
N
Ph
N
Zn
N
N
N
2
N
N
n
Cl Cl
n
Cl
Cl
2
Scheme 1
axial Zn–N(1) and Zn–N(5) bonds. The X-ray data reveal the
polymeric chain directed along axis x of the crystal.
The chain-forming element of symmetry is the plane of sliding
reflection and the repeating unit in the chain is the ZnL2 mole-
cular group. Atom N(8A) of the neighbouring molecule plays the
bridging role and rises the coordination number of Zn to five.
These chains form the layers which are parallel to crystallo-
†
Synthesis of 4,5-dichloro-2-phenyldiazenyl-1H-imidazole 1. 17.25 g
(0.125 mol) of 4,5-dichloroimidazole were dissolved in 600 ml of water
solution containing 30 g of Na2CO3 and 10 g of NaOH. The mixture was
cooled to 8°C and a solution of diazonium salt obtained by the common
procedure from aniline (11.4 g, 0.125 mol), concentrated HCl (31.25 ml)
and NaNO2 (9 g, 0.13 mol) was added under intense stirring for 20 min
with keeping the temperature in the range 6–10°C. The mixture was then
stirred for 1 h at room temperature and acidified with acetic acid to pH ~6.
The precipitate was filtered off, dried and recrystallized from acetonitrile
to furnish yellow-orange crystals of compound 1.Yield 64%, mp 166–167°C.
1H NMR (DMSO-d6) d: 7.47–7.56 (m, 3H, HAr), 7.86–7.89 (m, 2H, HAr),
14.06 (br.s, 1H, NH). Found (%): C, 44.98; H, 2.49; N, 23.29. Calc. for
C9H6N4Cl2 (%): C, 44.84; H, 2.51; N, 23.24.
§
Crystal data for 2: C18H10N8Cl4Zn, orange, prismatic, M = 545.5,
orthorhombic, space group Pna21, at 293 K: a = 11.118(3), b = 21.900(5) and
c = 9.512(4) Å, V = 2251(5) Å3, Z = 4, dcalc = 1.609, F(000) = 1088, m =
= 6.09 mm–1, R1 = 0.0550 for 1718 independent reflections with F > 4s(F0),
wR2 = 0.1682 for all data, GOF = 1.014. 2438 reflections (unique, Rint
=
= 0.083) were measured on an Enraf-Nonius Cad-4 diffractometer (CuKa-
radiation, graphite monochromator, q/2q scan mode, 2qmax = 60°).
The structure was determined by direct method and refined by full-matrix
least squares technique on F2 with anisotropic displacement parameters
for non-hydrogen atoms. One of Cl atoms was disordered by two posi-
tions. The hydrogen atoms were placed in calculated positions and refined
in the riding model with fixed isotropic displacement parameters. The
structure was solved by direct method SHELXS-8614 and refined by
the SHELXL-97 program.15
CCDC 772819 contains the supplementary crystallographic data for
this paper. These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
For details, see ‘Notice to Authors’, Mendeleev Commun., Issue 1, 2011.
‡
Synthesis of bis(4,5-dichloro-2-phenyldiazenyl-1H-imidazoleato)zinc(ii) 2.
A solution of zinc acetate dihydrate (0.219 g, 1 mmol) in methanol (5 ml)
was added to a solution of 1 (0.48 g, 2 mmol) in methanol (20 ml). The
mixture was refluxed for 2 h. The precipitate formed after cooling was
filtered off, washed with methanol and recrystallized from DMF to give
1
orange crystals. Yield 30%, mp > 250°C. H NMR (DMSO-d6) d: 7.39
(br.s, 10H, HAr). Found (%): C, 39.58; H, 1.76; N, 20.49; Zn, 12.10. Calc.
for C18H10N8Cl4Zn (%): C, 39.63; H, 1.85; N, 20.54; Zn, 11.98.
© 2011 Mendeleev Communications. All rights reserved.
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Mendeleev Commun., 2011, 21, 87–88
The polymeric structure of 2 results from the intermolecular
interaction of the central zinc atoms with donor nitrogen centres
of the imidazole moiety of the adjacent molecule. Such mode of
binding is met in crystal structures of some other metal complexes
of nitrogen-containing heterocycles.16–18 An example15 is tetra-
nuclear copper complexes with 1-alkyl-2-aryldiazenylimidazole
ligands, but the intermolecular coordination is furnished by nitro-
gen centres in the azo group. Bis(4,5-dichloro-2-phenyldiazenyl-
1H-imidazoleato)zinc is the first example of complexes in which
the polymeric structure is achieved via intermolecular Zn–N
coordination provided by heterocyclic nitrogen centres.
N(8B)
Zn(1A)
C(16)
C(8)
C(9)
C(15)
N(8A)
C(14)
C(7)
C(6)
C(17)
C(18)
C(5)
C(4)
C(13)
N(5)
N(1)
N(3)
C(3)
C(2)
Zn(1)
This work was supported by the grant of the President of
the Russian Federation (project NS 3233.2010.3) and the Rus-
sian Foundation for Basic Research (grant nos. 09-03-12109,
08-03-00154 and 08-03-00223).
N(2)
C(1)
N(6)
C(10)
N(7)
C(11)
C(12)
Cl(2)
N(4)
N(8)
Cl(3)
Cl(1)
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Cl(4)
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Figure 1 Fragment of the polymer 2. Selected bond lengths (Å) and angles
(°): Zn–N(3) 1.96, Zn–N(7) 2.04, Zn–N(1) 2.18, Zn–N(5) 2.25, Zn–N(8A)
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in the metal chelate five-membered rings form a plane with devia-
tions no more than 0.07Å. Two identical 2-phenyldiazenyl-1H-
imidazole ligands play different roles in the crystal: one of them
serves as a bidentate chelate whereas the second one participates
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C(17)
C(3)
Cl(2)
C(10)
N(6)
C(18)
N(5)
Cl(3)
N(7)
C(11)
N(3)
Cl(1)
Zn(1)
N(1)
C(2)
C(16)
C(15)
C(9)
C(1)
N(2)
C(4)
C(8)
C(7)
C(14)
N(4)
C(5)
C(6)
0
c
b
Figure 2 Crystal packing of polymeric complex 2.
Received: 27th September 2010; Com. 10/3602
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