Mercury(I) complexes with bidentate iminopyridine ligands: Synthesis, spectral characterization and structural analysis

Article abstract of DOI:10.1016/j.poly.2009.02.020

Four mercury(I) complexes, [L²HgHgL²](NO₃)₂ (L² = (4-fluorophenyl)pyridin-2-ylmethyleneamine, 1; (4-chlorophenyl)pyridin-2-ylmethyleneamine, 2; (4-bromophenyl)pyridin-2-ylmethyleneamine, 3 and (4-iodo

Full text of DOI:10.1016/j.poly.2009.02.020

Polyhedron 28 (2009) 1205–1210
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Mercury(I) complexes with bidentate iminopyridine ligands: Synthesis, spectral
characterization and structural analysis
b
b
Saeed Dehghanpour a, , Mehdi Khalaj , Ali Mahmoudi
*
a Department of Chemistry, Alzahra University, P.O. Box 1993891176, Tehran, Iran
b Department of Chemistry, Islamic Azad University, Karaj Branch, Karaj, Iran
a r t i c l e i n f o
a b s t r a c t
Four mercury(I) complexes, [L2HgHgL2](NO3)2 (L2 = (4-fluorophenyl)pyridin-2-ylmethyleneamine, 1; (4-
chlorophenyl)pyridin-2-ylmethyleneamine, 2; (4-bromophenyl)pyridin-2-ylmethyleneamine, 3 and (4-
iodophenyl)pyridin-2-ylmethyleneamine, 4) have been synthesized and characterized by CHN analysis,
IR and UV–Vis spectroscopy. The crystal structures of 1 and 3 were determined by single crystal X-ray
Article history:
Received 10 January 2009
Accepted 4 February 2009
Available online 3 March 2009
2þ
spectroscopy. These complexes contain the Hg2 moiety with a mercury–mercury bonded core, in which
Keywords:
one diimine ligand is coordinated to each mercury atom. The Hg atoms have an additional axial interac-
Mercury(I) complexes
2-Pyridinecarbaldehyde
Diimine ligands
ꢀ
tion with the oxygen atom of the NO3 anion in both complexes. Complex 1 shows a step in the Hg–Hg
bond due to the parallel configuration of the planar ligands. However, the ligand planes in the complex 3
are nearly planar and these planes are approximately perpendicular to each other. Supramolecular struc-
Crystal structures
tures were built in both complexes via
p–
p
stacking of the diimine ligands.
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
stabilizing low valent metal redox-states seem to be good candi-
dates for such studies and were used for the synthesis of Cu(I)
and Re(I) complexes [17,18]. According to this view, we describe
the synthesis and structural characterization of Hg(I) complexes
of the type [L2HgHgL2]2+ in which L2 is an unsymmetrical bidentate
iminopyridine ligand (Fig. 1).
The crystal chemistry of mercury(I)–nitrogen complexes with
2þ
the characteristic Hg2 dumbbell is more or less singular [1–3].
These complexes can be divided into systems with [L1HgHgL1]2+
,
[HgHgL2]2+, [L2HgHgL2]2+ and [(L2)2HgHg(L2)2]2+ cations (L1 and
L2 are mono- and bidentate nitrogen donor ligands, respectively).
The ligands such as pyridine and its derivatives form linear or
near-linear complexes of the type [L1HgHgL1]2+ [4–12]. An
[HgHgL2]2+ element is present in the asymmetric complex
Hg2(phen)(NO3)2, in which the bidentate phenanthroline ligand is
bound to one of the Hg centers [12]. An [L2HgHgL2]2+ kernel is ob-
2. Experimental
2.1. General
All chemicals were reagent grade and were used as received.
The solvents used for the reactions were purified by literature
methods [19]. The ligands (4-fluorophenyl)pyridin-2-ylmethyl-
ene-amine, A, (4-chlorophenyl)pyridin-2-ylmethyleneamine, B,
served
for
Hg2(phen)2(NO3)2
[9,13],
[Hg2(4-benzylpyri-
dine)4](ClO4)2 [14] and [Hg2(naphthyridine)2](ClO4)2 [15]. The
[L2HgHgL2]2+ core forms a nearly planar geometry with the bis-
bidentate pyrazolyl-pyridine ligand [16]. The complex [Hg2(phe-
n)4](OTf)2, in which eight N-donor atoms are coordinated to the
(4-bromophenyl)pyridin-2-ylmethyleneamine,
C
and (4-iodo-
phenyl)pyridin-2-ylmethyleneamine, D were prepared according
to reported procedures [20].
Elemental analyses were performed using a Heraeus CHN-O-
RAPID elemental analyzer. Infrared spectra were recorded on a
Bruker Tensor 27 instrument. Electronic absorption spectra were
dimercury(I) dumbbell, is
a single example containing the
[(L2)2HgHg(L2)2]2+ moiety [13]. Mercury(I) complexes with nitro-
gen ligands generally appear to be unstable, although there are a
few exceptions (for example, the above noted complexes). This
apparent instability has been attributed to the tendency of such li-
gands to induce dismutation of the mercury(I) ion due to the rela-
tively greater stability of the corresponding mercury(II) complexes.
recorded on a JASCO V-570 spectrophotometer; kmax(loge).
2.2. Syntheses
p-Acceptor ligands such as pyridine and phenanthroline are known
to form stable mercury(I) complexes [4]. Iminopyridine ligands
2.2.1. Synthesis of [Hg2(A)2](NO3)2 (1)
A solution of mercury(I) nitrate dihydrate (280 mg, 0.5 mmol)
* Corresponding author. Tel./fax: +98 21 88041344.
in absolute methanol (10 ml) was added to a solution of A
E-mail address: Dehganpour_farasha@yahoo.com (S. Dehghanpour).
0277-5387/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2009.02.020

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S. Dehghanpour et al. / Polyhedron 28 (2009) 1205–1210
Table 1
Crystal data and structure refinements for 1 and 3.
Complex
1
3
X
N
N
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
a (Å)
C24H18F2Hg2N6O6
925.62
150(1)
C24H18Br2Hg2N6O6
1047.44
100(2)
0.71073
monoclinic
C2/c
35.571(1)
7.1888(2)
26.781(8)
90
129.554(1)
90
5280(3)
8
2.635
14.696
3856
Hg
Hg
0.71073
(NO3)2
triclinic
ꢀ
P1
7.2680(2)
8.8507(2)
10.202(2)
97.52(3)
97.19(3)
102.04(3)
628.4(2)
1
2.446
12.270
430
0.14 ꢁ 0.11 ꢁ 0.03
N
N
X
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (A3)
Z
Complex
X
F
Cl
Br
I
Density (g cmꢀ3
)
l
(mmꢀ1
)
1
2
3
4
F(000)
Crystal size (mm3)
0.23 ꢁ 0.12 ꢁ 0.11
h range for data collection 2.88–27.47.
(°)
Index ranges
1.48–30.03
ꢀ9 6 h 6 9,
ꢀ11 6 k 6 11,
ꢀ12 6 l 6 13
5778
ꢀ49 6 h 6 50,
ꢀ10 6 k 6 10,
ꢀ37 6 l 6 37
32124
Fig. 1. Chemical formula of Hg(I) complexes 1–4.
Reflections collected
Independent reflections
2832 [0.0788]
7667 [0.0917]
(200 mg, 1 mmol) in methanol (10 ml). The resulting precipitate
that formed immediately was dissolved in hot absolute methanol
(20 ml). The filtered solution was cooled in the dark, giving the
complex as light yellow needles, which were washed successively
with ice-cooled absolute methanol (5 ml) and ether (25 ml), and
dried in a vacuum desiccator overnight. Yield: 92%. Anal. Calc. for
C24H18F2Hg2N6O6: C, 31.14; H, 1.96; N, 9.08. Found: C, 31.17; H,
[Rint
]
Completeness to h = 27.47° 98.1%
Absorption correction
99.4%
semi-empirical from
equivalents
semi-empirical from
equivalents
0.696 and 0.313
Maximum and minimum
transmission
Refinement method
0.1948 and 0.1331
Full-matrix least-
squares on F2
2832/0/181
Full-matrix least-squares
on F2
7667/0/361
1.95; N, 9.05%. UV–Vis: k(log
e) (DMSO): 243(4.11), 275(3.92),
Data/restraints/
parameters
295(3.91). IR (KBr/
m
, cmꢀ1): 1596 (C@N).
Goodness-of-fit (GOF) on
1.055
0.990
F2
2.2.2. Synthesis of [Hg2(B)2](NO3)2 (2)
Final R indices [I > 2
r
(I)]
R1 = 0.0577,
wR2 = 0.1404
R1 = 0.0739,
wR2 = 0.1518
4.521 and ꢀ4.235
R1 = 0.0427, wR2 = 0.0712
R1 = 0.0908, wR2 = 0.0837
2.518 and ꢀ2.406
This complex was prepared by a procedure similar to that for 1
using 21.7 mg (0.1 mmol) of B. Light yellow crystals were collected
by filtration and dried in vacuo. Yield: 93%. Anal. Calc. for
C24H18Cl2Hg2N6O6: C, 30.07; H, 1.89; N, 8.77. Found: C, 30.09; H,
R indices (all data)
Largest difference in peak
and hole (e Åꢀ3
)
1.87; N, 8.74%. UV–Vis: k(log
e) (DMSO): 240(4.21), 273(3.84),
297(3.71). IR (KBr/
m
, cmꢀ1): 1601 (C@N).
tion corrections were carried out using SORTAV [22]. The structure
was solved and refined using SHELXTL V6.1 [23] for full-matrix
least-squares refinement based on F2. All H-atoms were included
in calculated positions and allowed to refine in a riding-motion
approximation with Uiso tied to the carrier atom. Diffraction data
for 3 collected on a Bruker SMART APEX2 CCD area detector using
2.2.3. Synthesis of [Hg2(C)2](NO3)2 (3)
This complex was prepared by a procedure similar to that for 1
using 26.1 mg (0.1 mmol) of C. Light yellow crystals were collected
by filtration and dried in vacuo. Yield: 86%. Anal. Calc. for
C24H18Br2Hg2N6O6: C, 27.52; H, 1.73; N, 8.02. Found: C, 27.50; H,
1.72; N, 8.05%. UV–Vis: k(log
e) (DMSO): 239(4.23), 269(3.86),
298(3.86). IR (KBr/
m
, cmꢀ1): 1599 (C@N).
graphite monochromated Mo Ka radiation (k = 0.71073 Å). Preli-
minary orientation matrices were obtained from the first frames
using APEX2 [24]. The structures were solved using direct methods
and refined by the full-matrix least-squares method on F2 data
using SHELXTL [25]. All H-atoms were geometrically positioned and
refined using a riding model with d (C–H) = 0.93 Å, Uiso = 1.2Ueq(C).
2.2.4. Synthesis of [Hg2(D)2](NO3)2 (4)
This complex was prepared by a procedure similar to that for 1
using 30.8 mg (0.1 mmol) of D. Light yellow crystals were collected
by filtration and dried in vacuo. Yield: 89%. Anal. Calc. for
C24H18Hg2I2N6O6: C, 25.25; H, 1.59; N, 7.36. Found: C, 25.28; H,
1.56; N, 7.34%. UV–Vis: k(log
e
) (DMSO): 238(4.20), 272(3.81),
3. Results and discussion
296(3.95). IR (KBr/
m
, cmꢀ1): 1602 (C@N).
3.1. Synthesis and spectral properties
2.3. X-ray analyses
The mercury(I) complexes were prepared by reacting equimolar
quantities of mercury(I) nitrate and the ligands in methanol. These
complexes are light yellow solids, which are insoluble in chloro-
form, methanol, ethanol and acetone, and are stable under ambient
conditions. While most mercury(I) complexes containing nitrogen
donor ligands undergo disproportionation reactions, some imines
are known to form stable mercury(I) complexes [4,13]. The exis-
tence of stable iminopyridine complexes of mercury(I), which have
Crystals of 1 and 3, which were suitable for X-ray crystallogra-
phy, were obtained as described above. A summary of the key crys-
tallographic information is given in Table 1. Diffraction data for 1
was collected on a Bruker–Nonius Kappa-CCD diffractometer using
monochromated Mo K
tion of / scans and scans with
The data was processed using the Denzo-SMN package [21]. Absorp-
a
radiation and measured using a combina-
x
j
offsets to fill the Ewald sphere.

S. Dehghanpour et al. / Polyhedron 28 (2009) 1205–1210
1207
Table 2
3.2.1. [Hg2(A)2](NO3)2 (1)
Selected bond lengths (Å) and bond angles (°) for 1 and 3.
A view of the complex [Hg2(A)2](NO3)2, 1, along with the atom-
numbering scheme is shown in Fig. 2. Complex 1 has crystallo-
1
3
ꢀ
graphic 1 symmetry and the inversion center is located at the mid-
Hg1–Hg1a
Hg1–N1
Hg1–N2
Hg1–O1
2.5334(11)
2.317(9)
2.427(8)
2.490(9)
Hg1–Hg10
Hg1–N1
Hg1–N2
Hg1–O1
Hg1–N10
Hg1–N20
Hg1–O10
2.5190(7)
2.219(6)
2.565(7)
2.698(6)
2.292(6)
2.429(6)
2.569(6)
point of the Hg–Hg bond. Each mercury atom has essentially four
nearest neighboring atoms, namely the other mercury atom, two
nitrogen atoms of the diimine molecule and one oxygen atom
belonging to a nitrate ion. The Hg atoms in 1 have an irregular
coordination environment. The N1–Hg1–O1 and the intraligand
N1–Hg1–N2 angles are only 81.9(3)° and 70.4(3)°, respectively.
On the contrary, the Hg1a–Hg1–N1 and Hg1a–Hg1–N2 angles are
145.7(3)° and 134.9(2)°, respectively.
The average Hg–N bond distance (2.372 Å) is similar to that
found in structurally related complexes ([L2HgHgL2]2+ with two
N-donor atoms per Hg); for example: 2.335 Å for [Hg2(phe-
n)2](OTf)2, 2.39 Å for Hg2(phen)(NO3)2 [12], 2.356 Å for
[Hg2(LpPh)][ClO4]2, (LpPh = terdentate ligand, [bis(pyrazol-3-yl)pyr-
idine] derivative) [16] and 2.335 Å for [Hg2(phen)2](OTf)2 and
2.352 Å for Hg2(4-benzyl-py)4ClO4)2 [13,14]. However, the Hg–
N bond lengths in complexes of the type [L2HgHgL2]2+ lie be-
tween the same bond lengths in complexes of the type
[L1HgHgL1]2+ and [(L2)2HgHg(L2)2]2+. The Hg–N bond lengths ob-
served for complexes of the type [L1HgHgL1]2+ exhibit values in
the 2.10–2.20 Å range [4]. A mean value of 2.521 Å is observed
for the complex [Hg2(phen)4]2+ with four N-donor atoms per
Hg [13]. The diimine ligands in 1 are coordinated in a slightly
asymmetric bidentate manner: The difference between the bond
lengths of Hg1–N1 and Hg1–N2 is 0.11 Å. A similar asymmetry
has been reported for [Hg2(phen)2](OTf)2, with a difference of
0.14 Å [13].
N1–Hg1–N2
N1–Hg1–O1
N2–Hg1–O1
N1–Hg1–Hg1a
N2–Hg1–Hg1a
O1–Hg1–Hg1a
N3–O1–Hg1
70.4(3)
81.9(3)
75.3(3)
145.7(3)
134.9(2)
122.6(2)
119.2(7)
N1–Hg1–N2
N1–Hg1–O1
N2–Hg1–O1
N1–Hg1–Hg10
Hg10–Hg1–N2
Hg10–Hg1–O1
N3–O1–Hg1
N10–Hg10–N2
N10–Hg10–O10
N20–Hg10–O10
N10–Hg10–Hg1
N20–Hg10–Hg1
Hg1–Hg10–O10
N30–O10–Hg10
70.9(2)
83.2(2)
91.45(19)
163.48(16)
122.56(15)
104.62(14)
108.9(5)
70.7(2)
72.0(2)
88.7(2)
144.60(16)
133.72(14)
124.29(14)
110.1(4)
been confirmed in this study, is consistent with an earlier sugges-
tion that mercury(I) complexes should favor -acceptor ligands.
p
The IR spectra of the free ligands exhibit the characteristic band
of the imine group in the 1621–1631 cmꢀ1 region [20]. This band
is shifted to lower frequencies in the IR spectra of the correspond-
ing complexes due to the coordination of the imine nitrogen, and
appears in the 1596–1602 cmꢀ1 region.
The Hg1–O1 distance is 2.490(9) Å, compared to the sum of the
van der Waals radii of 3.02–3.25 Å. This distance is slightly shorter
than those in Hg2(phen)(NO3)2, (2.59 and 2.91 Å) [12] and in
Hg2(quinoline)2(NO3)2, (2.818, 2.786 and 2.802 Å) [26–29].
The Hg–Hg bond length of 1 is 2.5334(11) Å, compared to
2.513(5) Å for [Hg2(phen)2](OTf)2, 2.516(7) Å for Hg2(phen)(NO3)2
and 2.551(2) Å for Hg2(quinoline)2(NO3)2 [12,13,27].
The absorption spectra of the complexes 1–4 have absorption
bands in the 200–300 nm range (see experimental section) attrib-
*
p ? p or/and charge transfer transitions.
uted to ligand-centered
3.2. Crystal structures
The crystallographic data of compounds 1 and 3 are summa-
rized in Table 1 and selected bond distances and angles are given
in Table 2.
The geometry of imine and pyridine nitrogen atoms is planar.
The planarity is measured by three N atom bond angles. The sums
Fig. 2. Structure of 1 in the crystal, showing the atom-labelling scheme. Thermal ellipsoids are at 50% probability.

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S. Dehghanpour et al. / Polyhedron 28 (2009) 1205–1210
Table 3
Geometry of the pyridine, chelate and benzene ring in compounds 1 and 3.
1
3
Ligand 1
Ligand 2
Planes 1 (pyridine ring)
Planes 2 (chelate ring)
Planes 3 (benzene ring)
Dihedral angle/° between planes 1 and 2
Dihedral angle/° between planes 2 and 3
Dihedral angle/° between planes 1 and 3
Distance/Å of Hg (1) to the plane 1
Distance/Å of Hg (1a) to the plane 1
Torsion angle/° N–C@C–N (lig 1)
Angel between plane 1 and Hg–Hg line
N1–C5–C6–N2
N1–C2–C3–C4–C5.– N2
C7–C8–C9–C10–C11–C12
1.29(4)
2.10(3)
2.65(4)
0.1091(5)
1.089(5)
4.848(2)
67.25(4)
N1–C5–C6–N2
N1–C2–C3–C4–C5
C7–C8–C9–C10–C11–C12
5.88(3)
9.45(3)
6.19(3)
0.1193(5)
0.127(4)
4.197(2)
84.35(3)
N10–C50–C60–N20
N10–C20–C30–C40–C50
C70–C80–C90–C100–C110–C120
5.20(4)
7.59(3)
11.21(3)
0.0492(4)
0.816(4)
ꢀ9.073(2)
69.90(3)
Fig. 3. View of the [Hg2(A)2]2+ cation of complex 1 perpendicular to the Hg–Hg bond.
of these angles (
R
N) are 359.5° and 360° for N1 and N2, respec-
is displaced by 1.1 Å out of this plane, so that the [L2HgHgL2]2+ unit
has an appreciable ‘step’ in the Hg–Hg bond (Fig. 3).
tively. Despite the fact that the imine nitrogen atoms in 1 are sp2
hybridized, some strain in the chelate ring is suggested by the devi-
ation from the 120° angle about the nitrogen, Hg1–N2–C6
(114.6(7)°), Hg1–N2–C7 (124.3(7)°), and C6–N2–C7 (121.1(9)°).
Surprisingly, the dihedral angles between the planes of the pyr-
idine ring, chelate ring and the benzene ring (best plane of 1, 2 and
3, Table 3) in 1 show coplanarity of these planes, leading to a con-
siderable planarity of the ligands. The coplanarity of the pyridine
and chelate ring results in a bite size of 2.74 Å for d(N1–N2).
While the ligand is planar, the [L2HgHgL2]2+ cation of 1, as a
whole, is not coplanar. The mercury atom is closely within the
plane of the corresponding chelate diimine ligand (max. deviation
from this plane is 0.11 Å). However, the inversion-related mercury
[Hg2(A)2](NO3)2, 1, exhibits a supramolecular structure as a re-
sult of the
p–p stacking of the diimine ligands, and this may be
responsible for the insolubility of the complex. Each diimine ligand
has two diimine neighbors within the stacks, which are oriented
along the crystallographic, 111 plane (Fig. 4). The mean inter-ring
distances between corresponding atoms of the diimine ligands and
the two neighboring ligands are almost equal and amount to 3.42 Å
for the stacks involving the rings formed by the pyridine ring and
the neighboring benzene ring. A related stacking of the phenan-
throline ligands was observed for [Hg2(phen)2](OTf)2 with separa-
tions of approximately 3.45 Å [13] and 3.50 Å for Hg2(phen)(NO3)2
[12].
Fig. 4. Packing of [Hg2(A)2](NO3)2, 1.

S. Dehghanpour et al. / Polyhedron 28 (2009) 1205–1210
1209
between the bond lengths Hg1–N1 and Hg1–N2 is 0.346 and
0.137 Å between Hg10–N10 and Hg10–N20 (Table 2). However, the
average Hg–N bond length of 2.376 Å agrees well with the same
distance in the 1 (Hg–Nave = 2.372 Å).
The Hg–Hg bond length of 2.5190(7) Å in 3 is slightly shorter
than the same bond length in complex 1. However, the average
Hg–Hg bond distance of 1 and 3 is 2.526 Å, and the Hg–Hg bond
lengths in these complexes ([L2HgHgL2]2+) lie between the same
bond lengths in complexes of the type [L1HgHgL1]2+ (2.51 Å with
the exception of Hg2(quinoline)2(NO3)2, exhibiting a value of
2.551(2) Å) and complexes of the type [(L2)2HgHg(L2)2]2+ (2.549 Å).
The environment of each mercury atom differs in terms of mer-
cury–oxygen contacts. The Hg–O distances are 2.698(6) and
2.569(6) Å for Hg1–O1 and Hg10–O10, respectively. Whereas Hg1
is four coordinate, Hg10 has an additional relatively weak interac-
tion with another oxygen of the same nitrate atom [Hg10ꢂꢂꢂO20,
3.03 Å]. However, the Hg–O distances are longer than those in 1.
The dihedral angle between the plane of the chelate ring and
the pyridine ring (Table 3) indicate the coplanarity of these moie-
ties, resulting in a bite size of 2.788 and 2.735 Å for d(N1–N2) and
d(N10–N20).
A comparison of the dihedral angles between the planes of the
pyridine, chelate and the benzene ring (best plane of 1, 2 and 3, Ta-
ble 3) in 3 indicate that the ligand is distorted from planarity, with
an average twist of 8.5° between the chelate and the benzene
planes.
Fig. 5. Structure of 3 in the crystal, showing the atom-labelling scheme. Thermal
ellipsoids are at 50% probability.
In contrast with complex 1, the chelate ring of ligand 1 in com-
plex 3 twists around the Hg–Hg bond, such that it is approximately
perpendicular to the chelate ring of ligand 2, resulting in a dihedral
angle of 84.58° between the chelate rings (Fig. 6).
The mercury atom, Hg1 is closely coplanar with the diimine li-
gand. Deviation of the Hg (1) atom from this plane is 0.05 Å. How-
ever, Hg10 deviates considerably from this plane, by 0.816 Å.
As in complex 1, a related stacking of diimine ligands was ob-
served for 3 with separations of approximately 3.50 Å [13]. In the
structure of 3, each of the two diimine ligands is stacked with
one diimine ligand of a neighboring complex.
3.2.2. [Hg2(C)2](NO3)2 (3)
The molecular structure of 3 is illustrated in Fig. 5, where each
mercury atom is coordinated by the bidentate diimine ligand and
another mercury atom. The Hg–N distances of 3 cover the range
2.219(6)–2.565(7) Å, which is well within the van der Waals limit
of 3.05–3.28 Å, depending on the van der Waals radius of mercury
(1.50–1.73 Å) [28,29], while the Hg–N distances of 1 cover a short-
er range (2.317–2.427 Å). The diimine ligands in 3 are coordinated
in a considerably asymmetric bidentate manner: The difference
Fig. 6. View of the [Hg2(B)2]2+ cation of complex 3 along the Hg–Hg bond.

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S. Dehghanpour et al. / Polyhedron 28 (2009) 1205–1210
[9] G. Anderegg, Helv. Chim. Acta 42 (1959) 344.
4. Supplementary data
[10] J. Limmer, N. Hacke, K. Brodersen, Chem. Ber. 106 (1973) 2185.
[11] D.L. Kepert, D. Taylor, A.H. White, J. Chem. Soc., Dalton Trans. (1973) 893.
[12] R.C. Elder, J. Halpern, J.S. Pond, J. Am. Chem. Soc. 89 (1967) 6877.
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CCDC 714916 and 714917 contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or
from the Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
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Acknowledgment
Financial support by the Alzahra University is gratefully
acknowledged.
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