Synthesis and crystal structures of the Zn(II) and Co(II) complexes containing the reduced derivative nitronyl nitroxide

Article abstract of DOI:10.1134/S1070328411010155

Two complexes of formulas [Zn(Hfac)₂(IM-IMH-Bph)] (I) and [Co(Hfac)₃](IM-Bph) (II), where IM-Bph = 2,2′-bis(1′- oxyl-4′,4′,5′,5′-tetramethylimidazoline-2′-yl) -bis(2-formylphenyl) ether; Hfac = hexafluoroacetylacetonate, have been synthesized and characterized by single-crystal X-ray diffraction. The X-ray analysis demonstrates that both I and II are mononuclear complexes. In I, each zinc ion is five-coordinated with four oxygen atoms from two Hfac ligands and one oxygen atom from nitroxide. Complex II contains one Co(III) atom with six oxygen atoms from three Hfac ligands and uncoordinated IM-Bph diradical, in which the Co²⁺ ion and NIT-Bph biradical can undergo the redox reaction.

Full text of DOI:10.1134/S1070328411010155

ISSN 1070ꢀ3284, Russian Journal of Coordination Chemistry, 2011, Vol. 37, No. 2, pp. 111–116. © Pleiades Publishing, Ltd., 2011.
Synthesis and Crystal Structures of the Zn(II) and Co(II) Complexes
Containing the Reduced Derivative Nitronyl Nitroxide1
Y. F. Wanga, M. Q. Chengb, and L. Y. Wanga, *
a College of Chemistry and Chemical Engineering, Luoyang Normal University, Henan Luoyang 471000, P.R. China
b Department of Chemistry, Anshun Teacher’s College, Guizhou 561000, China
*eꢀmail: wlya@lynu.edu.cn
Received May 11, 2010
Abstract—Two complexes of formulas [Zn(Hfac)2(IMꢀIMHꢀBph)] (
where IMꢀBph = 2,2'ꢀbis(1'ꢀoxylꢀ4',4',5',5'ꢀtetramethylimidazolineꢀ2'ꢀyl)ꢀbis(2ꢀformylphenyl) ether;
Hfac = hexafluoroacetylacetonate, have been synthesized and characterized by singleꢀcrystal Xꢀray diffracꢀ
tion. The Xꢀray analysis demonstrates that both and II are mononuclear complexes. In , each zinc ion is
I) and [Co(Hfac)3](IMꢀBph) (II),
I
I
fiveꢀcoordinated with four oxygen atoms from two Hfac ligands and one oxygen atom from nitroxide. Comꢀ
plex II contains one Co(III) atom with six oxygen atoms from three Hfac ligands and uncoordinated IMꢀBph
diradical, in which the Co2+ ion and NITꢀBph biradical can undergo the redox reaction.
DOI: 10.1134/S1070328411010155
INTRODUCTION
when coordinated to transition metals [10, 11]. Most
of the systems studied to date use strongly acidic metal
ions (e.g., Hfac = hexafluoroacetylacetonate) to coorꢀ
dinated the weakly basic nitronyl nitroxide radicals to
the metal center [12].
The engineering of molecular magnets constitutes
a major contemporary research aim and has spawned
interest in organic radicals as building blocks for the
construction of new materials [1], and the popular
family concerns the nitronyl nitroxide radicals [2].
In present paper, we have synthesized and structurally
The synthesis and electronic properties of this family characterized complexes [Zn(Hfac)2(IMꢀIMHꢀBph)] (
were pioneered by Ullman three decade ago [3]. and [Co(Hfac)3](IMꢀBph) (II , where IMꢀBph =
Among them, the biradicals give rise to interesting 2,2'ꢀbis(1'ꢀoxylꢀ4',4',5',5'ꢀtetramethylimidꢀazolineꢀ2'ꢀyl)
I)
)
ꢀ
special properties [4–9], and one of the most interestꢀ bis(2ꢀformylphenyl) ether. The ligands IMꢀIMHꢀBph and
ing aspects of them is the chemical versatility, since IMꢀBph prepared as a result of the NITꢀBph reduction
this provides for a variety of molecular assemblies reaction according to the following scheme:
•
O
O
O
+e–
–
O
•
O
•
O
•
O
•
O
•
O
–
O
OH
N
N
N
N
N
N
N
N
N
N
N
N
NITꢀBph
IMꢀIMHꢀBph
IMꢀBph
Scheme.
1
The infrared spectra (4000–600 cm– ) were recorded
by using KBr pellets on an AvatarTM 360 E.S.P. IR
spectrometer.
EXPERIMENTAL
All reagents used in the syntheses were of analytical
grade and were used without further purification. Eleꢀ
mental analyses for carbon, hydrogen, and nitrogen
Synthesis of the complexes. All reagents were of anꢀ
were performed on a Vario EL III elemental analyzer. alytical grade NITꢀBph = 2,2'ꢀbis(3'ꢀoxideꢀ1'ꢀoxylꢀ
1
The article is published in the original.
111

112
WANG et al.
Table 1. Crystallographic data and details of the experiment and refinement for
I and II
Value
Parameter
Formula weight
I
II
929.05
291(2)
1128.66
291(2)
Temperature, K
Crystal system
Triclinic
Triclinic
Space group
P
1
P1
Unit cell dimensions:
a
, Å
, Å
14.6727(8)
16.2038(9)
19.0570(11)
102.6000(10)
105.4140(10)
93.4990(10)
4228.5(4)
4
11.9194(7)
13.5725(8)
15.2674(9)
92.1600(10)
95.2460(10)
91.8780(10)
2456.2(3)
2
b
c
, Å
, deg
, deg
, deg
α
β
γ
V
,
Å3
Z
ρcalcd, g/cm3
range for data collection, deg
1.459
1.526
θ
2.48 to 25.00
2.32 to 25.00
Independent reflections
Goodnessꢀofꢀfit on F2
15448 (Rint = 0.0141)
8994 (Rint = 0.0136)
1.030
1.033
Final
R
indices (
I
>
2σ
(I
))
R1 = 0.0668, wR2 = 0.1945
R1 = 0.0626, wR2 = 0.1702
Largest diff. peak and hole,
e
Å–3
0.733 and –0.489
0.534 and –0.450
4',4',5',5'ꢀtetramethylimidazolineꢀ2'ꢀyl)ꢀbis(2ꢀformylꢀ
phenyl) ether was prepared according to the literature
method [2, 3].
Xꢀray structure determination. A single crystal of I
and II were put on a Bruker SMART APEX II CCD
diffractometer equipped with a graphite monochroꢀ
mated Mo
Κ
radiation (
λ
= 0.71073 Å) by using
scan technique at room temperature. A total of 23020
int = 0.0141) for and 13429 ( int = 0.0136) for II, of
which 9893 and 6531 observed reflections with
were employed for structure refinements for
θ ω
/
α
Complex
as follows: Zn(Hfac)2 (1 mmol) was dissolved in boilꢀ
ing ꢀheptane (25 ml). The solution was left to boil for
30 min and then cooled down to 65 C, whereupon
I was prepared according to the methods
(
R
I
R
n
I
>
I
°
2
σ
(
I
)
and II, respectively. The structures were solved by
direct methods with SHELXSꢀ97 [13]. The hydrogen
atoms were assigned with common isotropic displaceꢀ
ment factors and included in the final refinement by
use of geometrical restrains, while the nonꢀhydrogen
atoms were treated with common anisotropic disꢀ
placement factors and included in the final refinement
with geomletrical restrains. A fullꢀmatrix leastꢀsquares
refinement on F2 was carried out using SHELXLꢀ97
0.5 mmol of NITꢀBph was slowly added with stirring
followed by 5 ml of CH2Cl2. The solution was allowed
to stand at room temperature for several days to give
dark red crystals. IR spectrum: 1384 s
ν
(N–O).
For C36H35F12N4O7Zn
anal.calcd.,%:
Found, %:
C, 46.54;
C, 46.52;
H, 3.80;
H, 3.79;
N, 6.03.
N, 6.04.
[14]. The final agreement factor values are
R
= 0.0668
2
and wR = 0.1945 (
2.8781 , where
agreement factor values are
w
= 1/[
σ
(
F
o)2 + (0.1202 )2 +
P
In the same way brown complex II was obtained.
IR spectrum: 1378 s (N–O).
F 2 + 2F 2
3
)
ν
P]
P
=
) for . The final
I
(
)
o
c
R
= 0.0626 and wR
=
P],
For C41H35CoF18N4O9
2
0.1702 (
w
= 1/[
σ
(F
o)2 + (0.0941 )2 + 2.0492
P
anal. calcd., %:
Found, %:
C, 43.63;
C, 43.61;
H, 3.13;
H, 3.11;
N, 4.96.
N, 4.98.
F 2 + 2F 2
where
P
=
) for II.
3
)
(
)
c
o
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 37
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2011

SYNTHESIS AND CRYSTAL STRUCTURES OF THE ZN(II) AND CO(II) COMPLEXES
Table 2. Selected bond distances and angles for and II
113
I
Bond
d
, Å
Bond
d, Å
I
Zn(1)–O(6)
Zn(1)–O(4)
Zn(1)–N(2)
Zn(1)–O(5)
Zn(1)–O(7)
O(1)–N(1)
1.984(4)
1.994(4)
2.046(5)
2.063(4)
2.087(4)
1.218(7)
N(2)–C(7)
N(2)–C(9)
N(3)–C(7)
N(3)–C(8)
O(3)–N(3)
O(2)–N(1)
1.305(8)
1.514(9)
1.375(8)
1.457(12)
1.278(8)
1.210(7)
II
Co(1)–O(4)
Co(1)–O(5)
Co(1)–O(6)
Co(1)–O(7)
Co(1)–O(8)
2.054(3)
2.062(3)
2.063(3)
2.063(3)
2.073(3)
Co(1)–O(9)
O(1)–N(1)
O(2)–C(14)
O(2)–C(1)
O(3)–N(3)
2.097(3)
1.377(4)
1.386(4)
1.387(4)
1.268(4)
Angle
ω
, deg
Angle
ω
, deg
I
O(6)Zn(1)O(4)
O(6)Zn(1)N(2)
O(4)Zn(1)N(2)
O(6)Zn(1)O(5)
O(4)Zn(1)O(5)
114.54(19)
125.0(2)
N(2)Zn(1)O(5)
O(6)Zn(1)O(7)
O(4)Zn(1)O(7)
N(2)Zn(1)O(7)
O(5)Zn(1)O(7)
90.48(18)
88.22(16)
91.24(17)
89.16(16)
179.54(17)
120.48(19)
92.21(18)
88.70(19)
II
O(4)Co(1)O(6)
O(5)Co(1)O(6)
O(4)Co(1)O(7)
O(5)Co(1)O(7)
O(6)Co(1)O(7)
175.51(11)
90.11(12)
88.29(11)
89.00(12)
87.66(11)
O(4)Co(1)O(8)
O(5)Co(1)O(8)
O(6)Co(1)O(8)
O(7)Co(1)O(8)
O(4)Co(1)O(9)
95.51(12)
90.22(11)
88.51(12)
176.09(11)
93.47(11)
The crystal data and experimental parameters for
I
characteristic of the stretching vibration of the N–H
and II are given in Table 1. The selected bond lengths group. The reduction of nitronyl nitroxide radicals in
and angles of
The atomic coordinates and other parameters of
structure and II have been deposited with the Camꢀ
I
and II are given in Table 2.
the presence of [Mn(Hfac)2] has already been
described [15].
I
The crystal structure of complex
I is shown in
bridge Crystaliographic Data Centre (nos. 63793 and
63794, respectively; deposit@ccdc.cainꢀac.uk or
http://www.ccdc.cam.ac.uk).
Fig. 1. Complex is found to contain two crystalloꢀ
I
graphically independent molecules, but these two
structures are not significantly different from each
other. The zinc(II) with the IMꢀIMHꢀBph ligand
forms a distorted squareꢀpyramidal complex with the
N atom of the ligand at the apical position and the
RESULTS AND DISCUSSION
The reaction is the partial reduction of the NITꢀBph Zn2+ ion, lying 0.691 Å above the basal plane, and the
diradical to the monoradical (IMꢀIMHꢀBph) takes base plane of the configuration is formed by four OHfac
place (Scheme). This fact was confirmed by Xꢀray (O(4), O(5), O(6), and O(7)) atoms. The reduced radꢀ
structure analysis and the IR spectrum of complex II
,
ical binds to the Zn2+ ion through the N(1) atom of the
which exhibited an absorption peak at 3349.6 cm–1 amidinoꢀoxide group. The Zn(1)–N(1) bond length is
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 37
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114
WANG et al.
C(58)
C(22)
C(57)
N(8)
C(21)
N(4)
N(7)
N(3)
O(10)
O(8)
C(56)
O(1)
O(3)
C(20)
C(55)
O(9)
C(9)
C(8)
C(45)
C(19)
C(54)
C(53)
N(6)
C(43)
N(2)
C(7)
O(2)
C(1)
C(18)
C(17)
C(37)
C(50)
C(42)
C(44)
N(5)
C(14)
N(1)
C(5)
C(38)
C(6)
C(2)
C(15)
C(52)
C(41)
C(51)
C(16)
C(3)
C(39)
O(14)
C(4)
Zn(2)
O(4)
C(40)
O(7)
O(12)
C(28)
Zn(1)
C(35)
C(70)
O(5)
C(71)
O(11)
O(13)
O(6)
C(30)
C(17)
C(29)
C(69)
C(33)
C(34)
C(64)
C(65)
Fig. 1. Molecular structure of
I, hydrogen and fluorine atoms are omitted for clarity.
O(3)
O(3)
H(53)
H(39)
O(1)
H(53)
C(53)
O(8)
C(3)
C(53)
H(3)
Fig. 2. Intermolecular hydrogen bonding of I.
1.998 Å, which is shorter than that of previously One NITꢀBph was reduced to IMꢀBph, and Co2+ ion
reported [16]. The angles of the O(4)Zn(1)O(7) is was oxidated to the Co3+ ion at the same time, and
168.7
°
, while the O(5)Zn(1)O(6) angle is more bent similar phenomenon had appeared in the other comꢀ
). The N(2)–O(1) bond length is 1.400(4) Å. plexes with nitroxide radicals [17]. Its reaction mechꢀ
(
151.4
°
The intermolecular H bonds occur between oxygen anisms are not completely clear. It may involve the
atoms of the uncoordinated NO moiety of nitronyl redox reaction between radicals. In order to extend
nitroxide and H–C from the benzimidazlyl ring our knowledge of chemistry of such systems, it is necꢀ
(
C(53)–H(53)···O 32.696, C(39)–H(39)···O(1) 2.762, essary to further explore the reaction mechanisms.
C(3)–H(3)···O(8) 2.727 Å). In the unit cell, the sinꢀ
gleꢀdouble hydrogen bonds are alternatively arranged,
resulting in a oneꢀdimensional chain structure
(Fig. 2).
The crystal structure consists of the [Co(Hfac)3
]
moiety and the uncoordinated IMꢀBph diradical. The
Co3+ ion is sixꢀcoordinate and has a distorted octaheꢀ
dral configuration, three Hfac ligands coordinate to
As shown in Fig. 3, the corresponding IMꢀBph the Co3+ ion through their oxygen atoms (O(4), O(5),
molecule and Co3+ ion were found in compound II
.
O(6), O(7), O(8), and O(9)) from the equatorial and
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 37
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SYNTHESIS AND CRYSTAL STRUCTURES OF THE ZN(II) AND CO(II) COMPLEXES
115
F(3)
F(5)
F(4)
F(2)
C(27)
C(29)
F(10)
C(10)
C(12)
N(1)
C(28)
C(30)
O(4)
F(12)
C(31)
C(9)
C(11)
C(8)
F(6)
F(1)
C(23)
C(21)
C(24)
O(1)
C(36)
C(35)
O(5)
F(11)
O(7)
N(4)
C(13)
C(6)
C(1)
C(7)
N(2)
Co(1)
C(34)
C(5)
C(26)
O(8)
C(22)
O(2)
C(33)
O(6)
C(5)
O(9)
F(13)
C(20)
C(25)
F(7)
F(8)
N(3)
C(32)
C(3)
C(2)
F(9)
C(40)
C(14)
C(18)
C(19)
C(15)
C(38)
C(37)
F(17)
O(3)
F(14)
C(16)
C(39)
F(16)
C(17)
C(41)
F(18)
F(15)
Fig. 3. View of II (for the sake of simplicity, the hydrogen and fluorine atoms have been omitted).
O(7)
O(7)
H(20B)
O(5)
H(10C)
H(10C)
O(4)
O(4)
H(17)
H(17)
H(17)
H(17)
O(4)
O(4)
H(10C)
H(10C)
O(5)
H(20B)
O(7)
O(7)
Fig. 4. Intermolecular hydrogen bonding of II
.
the axial position. The equatorial plane is composed of 1.377(4) Å for O(1)–N(1). The dihedral angle
four random oxygen atoms (for example O(4), O(6), between the two benzene rings is 85.70 , which is close
°
O(7), and O(8)), while the atoms O(5) and O(9) to that of the free radical NITꢀBph. There are two
occupy the axial positions. The average distance of the kinds of intermolecular H bonds, they occurred: (i)
Co(III)–O bonds is 2.069(7) Å, which are in the norꢀ between oxygen atoms of Hfac ligands and H–C from
mal range. The Co3+ ion is nearly coplanar with a the benzimidazolyl ring (C(17)–H(17)···O(4) 2.91 Å);
equatorial plane with the displacement average value (ii) between oxygen atoms of Hfac ligands and
of 0.0283 Å. The angles, such as O(4)Co(1)O(6) from methyl (C(10)–H(10)···O(7) 2.56 Å). As a result,
175.51(11) ) and O(5)Co(1)O(6) (90.11(12) ), are Co(Hfac)3] and IMꢀBph diradical are connected by
close to ideal values of 180 and 90 . Uncoordinated intermolecular H bonds to form a 2D network plane
H⎯C
(
°
°
[
°
°
N–O bond lengths of 1.268(4) Å for O(3)–N(3) and (Fig. 4).
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 37
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116
WANG et al.
8. Wautelet, J., Moigne, L., Videva, V., et al., J. Org.
ACKNOWLEDGMENTS
Chem., 2003, vol. 68, p. 8025.
This work was supported by the National Natural
Science Foundation of China (no. 20771054).
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2003, vol. 22, p. 1935.
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