Lanthanum(III) complexes with phenylcyanamide ligands: Synthesis and crystal structure

Article abstract of DOI:10.1016/j.ica.2011.10.050

Several novel mixed ligand lanthanum complexes with 1,10-phenantroline and phenylcyanamide derivatives with the formula of [La(phen)₃Cl ₃·OH₂] (1) and [La(phen)₃L₃] (phen = 1,10-phenantroline; L = 2-clorophenylcyanamide (2), 2,5- dichlorophenylcyanamide (3), 2,4-dichlorophenycyanamide (4) and 2,4,5-trichorophenycyanamide (5)) are successfully synthesized in aqueous solution. The complexes are characterized by spectroscopic analysis such as infrared, ¹H NMR, UV-Vis spectroscopy as well as elemental analysis. The molecular structure of 3 is determined by single-crystal X-ray diffraction method. Three 2,5-Cl₂pcyd and three phenanthroline ligands are coordinated to the central La atom in monodentate and bidentate manner, respectively.

Full text of DOI:10.1016/j.ica.2011.10.050

Inorganica Chimica Acta 383 (2012) 72–77
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Lanthanum(III) complexes with phenylcyanamide ligands: Synthesis and crystal
structure
a
a
b
Mozhgan Khorasani-Motlagh a, , Meissam Noroozifar , Sona Niroomand , Brian O. Patrick
⇑
a Department of Chemistry, University of Sistan & Baluchestan, P.O. Box 98155-147, Zahedan, Iran
b Department of Chemistry, University of British Columbia, Vancouver, Canada
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 14 June 2011
Received in revised form 7 October 2011
Accepted 13 October 2011
Available online 21 October 2011
Several novel mixed ligand lanthanum complexes with 1,10-phenantroline and phenylcyanamide deriv-
atives with the formula of [La(phen)3Cl3ꢀOH2] (1) and [La(phen)3L3] (phen = 1,10-phenantroline; L =
2-clorophenylcyanamide (2), 2,5-dichlorophenylcyanamide (3), 2,4-dichlorophenycyanamide (4) and
2,4,5-trichorophenycyanamide (5)) are successfully synthesized in aqueous solution. The complexes
are characterized by spectroscopic analysis such as infrared, 1H NMR, UV–Vis spectroscopy as well as ele-
mental analysis. The molecular structure of 3 is determined by single-crystal X-ray diffraction method.
Three 2,5-Cl2pcyd and three phenanthroline ligands are coordinated to the central La atom in monoden-
tate and bidentate manner, respectively.
Keywords:
Lanthanum(III)
1,10-Phenantroline
Cyanamide
Ó 2011 Elsevier B.V. All rights reserved.
Coordination compounds
1. Introduction
but no crystal structure was reported [12,13]. Furthermore, Khan
and Iftikhar reported a number of 1,10-phenanthroline complexes
In recent years, coordination chemistry of the rare earth ele-
ments has undergone remarkable growth, and a wide variety of
geometries and coordination numbers have been observed. Low
crystal effects of the 4f electronic configurations and the large ionic
radii of these metal ions, which change considerably with atomic
number or oxidation state of the lanthanides, lead to the structural
versatility of these complexes [1].
with typical stochiometry [La(phen)2(H2O)xCl3]ꢀxH2O and studied
their spectroscopic properties [14]. The crystal structures of more
analogs of phenanthroline with lanthanides were reported by Lin-
Pei Jin in 2003, Udai P. Singh in 2007, and other researchers [15–17].
The chemistry of phenylcyanamide attracts attention for the
active role of its ligands in inorganic chemistry [18]. Material engi-
neers are noticing the generation of novel electronic, magnetic and
Moreover, synthesis of lanthanide metal complexes has been a
subject of rapid development in material and supramolecular
chemistry due to their many structural motifs, high coordination
numbers, and interesting magnetic, electronic, and spectroscopic
properties [2]. Lanthanide (4f) complexes are extensively used in
many applications [3] such as: chromophores for catalysts for
organic syntheses in the field of organometallic chemistry [4],
luminescent probes [5,6], NMR shift reagents [7], contrast agents
for magnetic resonance imaging (MRI) [8], and artificial enzymatic
‘‘scissors’’ of DNA and RNA in the field of biochemistry [9]. Lantha-
nide ions are different in the optical properties from other lumines-
cence materials because their absorbance and emission spectra
have narrow wavelength ranges with high quantum yields [10,11].
1,10-Phenanthroline (phen) forms a variety of complexes with
rare earth elements. One of the first complexes of this type was
reported by Hart and Laming [12,13]. They proposed the formula
of [Ln(phen)2Cl3OH2] and [Ln(phen)3(NCS)3] for this complexes
photonic devices. Extension of the p-electronic molecular structure
is one of the most important and promising approaches to achieve
high conductivity and strong effective magnetic coupling [19]. For
this aim, several complexes of phenycyanamide ligands with some
transition metals have been synthesized and the electronic proper-
ties of cyanamide group, especially its large
have been investigated [19–27].
p-conjugated system,
However, phenylcyanamide ligands were not used with rare
earth elements until we used them as N-donor ligands for synthesis
of new lanthanide complexes. We prepared novel complexes of Nd
and Pr with 1,10-phenanthroline and phenylcyanamide as mixed li-
gands in our previous works [28,29]. Here we report the synthesis of
new lanthanum complexes of phenanthroline and phenylcyana-
mide derivatives and investigate the crystal structure of
[La(phen)3(2,5-pcyd)3]. To our knowledge, this is the first crystal
structure of lanthanide complexes with cyanamide ligand.
2. Experimental
⇑
All reagents and solvents used in this work were purchased
from Merck and Aldrich Chem. Co. Phenylcyanamide ligands and
Corresponding author. Tel./fax: +98 541 241 7336.
E-mail address: mkhorasani@chem.usb.ac.ir (M. Khorasani-Motlagh).
0020-1693/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2011.10.050

M. Khorasani-Motlagh et al. / Inorganica Chimica Acta 383 (2012) 72–77
73
Fig. 1. ORTEP drawing of [La(phen)3(2,5-Cl2pcyd)3].
Table 1
their thallium salts were synthesized by the literature method [20].
The crystal data and experimental details of [La(phen)3(2,5-Cl2pcyd)3]ꢀCH2Cl2.
Caution: Thallium is extremely toxic.
UV–Vis spectra were recorded on an Analytikjena SPECORD
S-100 spectrometer with a photodiode array detector. IR spectra
were recorded as KBr disks on a Shimatzu IR instrument. NMR
experiments were recorded at room temperature in D2O and CDCl3
on a Bruker AV-500 spectrometer using an internal deuterated sol-
vent lock.
Empirical formula
Formula weight
Crystal system
Dimension
Space group
a (Å)
C57.83H34.65N12Cl7.65La
1307.67
monoclinic
0.12 ꢂ 0.25 ꢂ 0.35 mm
C2/c (#15)
19.459(2)
b (Å)
c (Å)
13.486(1)
41.464(4)
a
b (°)
(°)
90
103.37(3)
2.1. X-ray determination
c
(°)
90
10632(2)
8
V (Å3)
Z
Colorless crystals of [La(phen)3(2,5-Cl2pcyd)3]. CH2Cl2 (3) were
grown by diethyl ether diffusion into a dichloromethane solution
of the complex for several days. All measurements were made on
a Bruker APEX DUO diffractometer with graphite monochromated
T (°C)
D (gcm3)
F(000)
ꢁ180.0
1.634
5221.00
12.42
12879 (Rint = 0.060)
R1 = 0.079; wR2 = 0.171
R1 = 0.088; wR2 = 0.174
1.31
l
(cmꢁ1
)
Mo K
ꢁ180.0 0.1 °C to a maximum 2h value of 56.2° in a series of /
and scans in 0.50° oscillations with 15.0-s exposures. The crys-
a radiation. The data were collected at a temperature of
Number of unique data
Final R indices [I > 2 (I)]
Final R indices(for all data)
r
x
tal-to-detector distance was 70.00 mm. Of the 91864 reflections
that were collected, 12879 were unique (Rint = 0.060); equivalent
reflections were merged. Data were collected and integrated using
the Bruker SAINT software package. The linear absorption coefficient,
Goodness-of-fit (GOF)
p
2
R1
¼
RjjFoj ꢁ jFcjj=
R
jFoj; wR2
¼
R
ðwðF2o ꢁ F2c Þ Þ=
R
wðF2o Þ.
l
, for Mo Ka
radiation was 12.42 cmꢁ1. Data were corrected for
absorption effects using the multi-scan technique (SADABS), with
minimum and maximum transmission coefficients of 0.782 and
0.862, respectively.
Crystallographic data for [La(phen)3(2,5-Cl2pcyd)3]ꢀCH2Cl2 are
given in Table 1. Selected interaction distances and angles are
given in Table 2.
The structure was solved by direct methods [30]. The material
was crystallized with methylene chloride. Additionally, one ligand
was disordered and was modeled in two orientations. The solvent
molecule was only present with a relative population of 0.83. Final-
ly, the material appeared to be very marginally twinned, with the
two twin components related by a 180° rotation about the [ꢁ201]
reciprocal lattice direction. All non-hydrogen atoms, except those
of the minor disordered fragment, were refined anisotropically.
All hydrogen atoms were placed in calculated positions but were
not refined. A perspective view of complex 3 is shown in Fig. 1.
2.2. Synthesis
2.2.1. Synthesis of [La(phen)3Cl3ꢀOH2] (1)
[La(phen)3Cl3ꢀOH2] was synthesized by literature method [12]
but the excess amount of 1,10-phen was used, as it was dissolved
in the minimum amount of absolute ethanol and added drop wise
to an ethanolic solution of LaCl3ꢀ7H2O (200 mg) while stirred and
heated to 60 °C. The resulting solution was refluxed for 8 h in order

74
M. Khorasani-Motlagh et al. / Inorganica Chimica Acta 383 (2012) 72–77
Table 2
The selected geometric parameters, band lengths
55.29; H, 2.67; N, 13.58. Found: C, 55.18; H, 2.49; N, 13.38%. IR
(KBr): v(NCN) = 2115 cmꢁ1, UV–Vis absorption spectrum (CH2Cl2):
234, 267 nm. 1H NMR (CDCl3) ppm: 9.45, 8.27, 7.80, 7.62 (phen-H);
7.31, 6.58–7.10 (pcyd-H).
and
angles
(Å,
°)
of
[La(phen)3(2,5-
Cl2pcyd)3]CH2Cl2.
Band length
N(2)–La(1)
N(3)–La(1)
N(4)–La(1)
N(5)–La(1)
N(6)–La(1)
N(7)–La(1)
N(9)–La(1)
N(11)–La(1)
C(37)–N(7)
C(37)–N(8)
C(38)–N(8)
C(44)–N(9)
C(44)–N(10)
C(45)–N(10)
C(51)–N(11)
C(51)–N(12)
C(52)–N(12)
2.825(6)
2.782(5)
2.743(5)
2.749(5)
2.740(6)
2.546(6)
2.552(6)
2.532(6)
1.177(9)
1.291(9)
1.392(9)
1.176(9)
1.298(9)
1.377(9)
1.161(9)
1.296(9)
1.374(10)
2.2.5. Synthesis of [La(phen)3(2,4,5-Cl3pcyd)3] (5)
This was prepared by the procedure used for La(phen)3(2-
Clpcyd)3] except that the Tl[2,4,5-Cl3pcyd] ligand replaced Tl[2-
Clpcyd]. (Yield: 140 mg, 80%). Anal. Calc. for LaC57H30N12Cl9: C,
51.03; H, 2.38; N, 12.53. Found: C, 49.8; H, 2.23; N, 12.41%. IR
(KBr): v(NCN) = 2100 cmꢁ1, UV–Vis absorption spectrum (CH2Cl2):
234, 266 nm. 1H NMR (CDCl3) ppm: 9.25, 8.11, 7.58, 7.49 (phen-H);
6.84, 6.06 (pcyd-H).
3. Results and discussion
3.1. Synthesis and characterization of 1–5 complexes
Band angle
N(9)–C(44)–N(10)
N(11)–C(51)–N(12)
C(37)–N(7)–La(1)
C(37)–N(8)–C(38)
C(44)–N(9)–La(1)
C(44)–N(10)–C(45)
C(51)–N(11)–La(1)
C(51)–N(12)–C(52)
175.1(8)
169.1(7)
137.1(5)
120.0(6)
150.4(5)
118.0(6)
162.7(5)
122.6(7)
The lanthanide ions are well-known for having a variety of coor-
dination numbers which range from 3 to 12. Because of their large
ionic radii and the ionic nature of the metal–ligand bonding, triva-
lent lanthanide ions usually form complexes of higher coordination
numbers of typically 8 and 9 [31]. In this work, lanthanum(III) as a
lanthanide ion, phenylcyanamide and phen as coordinated ligand
were used to prepare various lanthanide complexes with different
coordination sphere and coordination numbers. The reaction of
aqueous solutions of lanthanum(III) complex [La(phen)3Cl3ꢀOH2]
(1), with thallium phenylcyanamide salts led to the preparation
of [La(phen)3(L)3] (L = 2-Clpcyd (2), 2,5-Cl2pcyd (3), 2,4-Cl2pcyd
(4), 2,4,5-Cl3pcyd (5)) (Scheme 1). Analytical, infrared and crystal-
lographic studies of these complexes have shown they are anhy-
drous. All of the complexes were air stable for extended periods.
Complex (1) was soluble in polarized solvents such as water and
methanol and insoluble in most organic solvents. Complexes
(2–5) were soluble in dichloromethane and chloroform; slightly
soluble in ethanol and methanol; insoluble in water and diethyl
ether, and they indicated similar behavior in non-coordinating
solvents, particularly dichloromethane and chloroform.
to complete the reaction. The resulting white precipitate was fil-
tered and washed several times by ethanol and dichloromethane.
The product was dried in a vacuum over P4O10 for several hours
(Yield: 190 mg, 88%). Anal. Calc. for LaC36H26N6Cl3O: C, 53.77; H,
3.24; N, 10.45. Found: C, 53.14; H, 3.04; N, 10.06%. IR (KBr):
m
(C@N) = 1421–1548 cmꢁ1
; m(C–H) = 725–847, UV–Vis absorption
(MeOH): 232, 266 nm. 1H NMR (D2O) ppm: 8.63, 7.77, 7.29, 7.06
(phen-H).
2.2.2. Synthesis of [La(phen)3(2-Clpcyd)3] (2)
The excess amount of Tl[2-Clpcyd] ligand was dissolved in hot
water, was cooled to 50 °C, was added to the aqueous solution of
[La(phen)3Cl3ꢀOH2] (100 mg), and was then stirred for 2 h at
50 °C. The reaction mixture that contained TlCl and product was
filtered, and the precipitates were washed with hot water several
times. The resulting yellow solid was re-crystallized by dissolving
it in a minimum volume of dichloromethane and slowly adding
diethyl ether to precipitate the product. The product was dried in
a vacuum over P4O10 for several hours (Yield: 100 mg, 68%). Anal.
Calc. for LaC57H36N12Cl3: C, 60.35; H, 3.18; N, 14.82. Found: C,
60.24; H, 3.08; N, 14.69%. IR (KBr): v(NCN) = 2110 cmꢁ1, UV–Vis
absorption (CH2Cl2): 232, 266 nm. 1H NMR (CDCl3) ppm: 9.19,
8.27, 7.81, 7.61 (phen-H); 6.85–7.12 (pcyd-H).
[La(phen)3Cl3.OH2] + 3TlL
[La(phen)3L3]
3TlCl
+
(1)
Cl
Cl
NCN
NCN
Cl
(2)
(3)
2.2.3. Synthesis of [La(phen)3(2,5-Cl2pcyd)3] (3)
Cl
Cl
This was prepared by the procedure used for La(phen)3(2-
Clpcyd)3] except that the Tl[2,5-Cl2pcyd] ligand replaced Tl[2-
Clpcyd]. (Yield: 120 mg, 75%). Anal. Calc. for LaC57H33N12Cl6: C,
55.29; H, 2.67; N, 13.58. Found: C, 55.14; H, 2.53; N, 13.43%. IR
(KBr): v(NCN) = 2100 cmꢁ1, UV–Vis absorption spectrum (CH2Cl2):
239, 285 nm. 1H NMR (CDCl3) ppm: 9.37, 8.20, 7.69, 7.57 (phen-H);
6.92, 6.43, 6.18 (pcyd-H).
L =
NCN
NCN
Cl
Cl
Cl
2.2.4. Synthesis of [La(phen)3(2,4-Cl2pcyd)3] (4)
(5)
(4)
This was prepared by the procedure used for La(phen)3(2-
Clpcyd)3] except that the Tl[2,4-Cl2pcyd] ligand replaced Tl[2-
Clpcyd] (Yield: 135 mg, 84%). Anal. Calc. for LaC57H33N12Cl6: C,
Scheme 1. The reaction of 1 with thallium phenylcyanamide salts.

M. Khorasani-Motlagh et al. / Inorganica Chimica Acta 383 (2012) 72–77
75
Table 3
Infrared absorption frequencies (cmꢁ1) of cyanamide group.
Table 4
1H NMR data for (1–5) complexes (in ppm).
b
Complex
m(NCN) Tl salt
m
(NCN) Free
m(NCN)
Complex
H of phena
H of pcyd
ligand
2
3
4
5
[La(phen)3(2-
Clpcyd)3]
[La(phen)3(2,5-
Cl2pcyd)3]
[La(phen)3(2,4-
Cl2pcyd)3]
[La(phen)3(2,4,5-
Cl3pcyd)3]
2110
2100
2115
2100
Tl[2-pcyd]
2090
2110
2100
2075
2-Clpcyd
2235
2235
2230
2230
[La(phen)3Cl3ꢀOH2]
[La(phen)3(2-Clpcyd)3]
[La(phen)3(2,5-Cl2pcyd)3]
[La(phen)3(2,4-Cl2pcyd)3]
[La(phen)3(2,4,5-Cl3pcyd)3]
Phen(D2O)
8.63
9.19
9.37
9.45
9.25
8.90
9.19
7.06
7.61
7.57
7.62
7.49
7.60
7.63
7.77
8.27
8.20
8.27
8.11
8.23
8.24
7.29
7.81
7.69
7.80
7.58
7.65
7.83
–
6.85–7.12
6.92, 6.43, 6.18
6.58–7.10, 7.31
6.84, 6.06
–
–
Tl[2,5-
Cl2pcyd]
Tl[2,4-
Cl2pcyd]
Tl[2,4,5-
Cl3pcyd]
2,5-
Cl2pcyd
2,4-
Cl2pcyd
2,4,5-
Cl3pcyd
Phen(CDCl3)
a
5
4
The IR spectrum of free 1,10-phenanthroline underwent a mod-
ification when coordinated with a lanthanide. The strong CH out-
of-plane bending absorptions of phen at 849 cmꢁ1 and 732 cmꢁ1
were lowered to 847 cmꢁ1 and 725 cmꢁ1 in complex (1) so that
the latter band became a doublet after complexation [12]. The
3
N
N
2
1,10-phenanthroline
m
(C@C) and
at 1421–1513 cmꢁ1 and 1584 cmꢁ1 compared to the free ligand
values of 1418–1502 cmꢁ1 and 1558–1642 cmꢁ1
respectively
m(C@N) modes of phen appeared as intensive bands
b
,
2
NCN
[32]. These bands were shifted to higher wave numbers on com-
plexation, which was due to the interaction between the lantha-
num(III) ion and the nitrogen atoms of phen. The bands at 651
3
4
6
and 604 cmꢁ1 attributed to
m(La–N) indicate the coordination of
nitrogen to the central ion [33]. The broad peaks at 1637 cmꢁ1
and in the 3050–3330 cmꢁ1 region may be assigned to the bending
and stretching vibrations of coordinated water [34].
5
Phenylcyanamide
Also, IR spectroscopy is a useful method for the characterization
of phenylcyanamide metal complexes. The principal absorption
frequencies and assignments [35] for all compounds are collected
in Table 3. IR spectroscopy can diagnose nitrile versus amine coor-
dination in both the anionic and natural forms of phenylcyana-
mide. In Neutral phenylcyanamide, the C„N band has been
observed in the range of 2225–2249 cmꢁ1, whereas a strong band
in the frequency lower than 2150 cmꢁ1 can be detected for N@C@N
vibration if the coordination of anionic phenylcyanamide ligands
to metal center occurs via nitrile nitrogen [20]. The IR spectra of
(2–5) were relatively similar. The strong band observed at 2230–
The absorption spectra of complex (1) and its cyanamide deriv-
atives were obtained in the methanol and dichloromethane sol-
vents, respectively. The UV–Visible spectrum of (4) is shown in
Fig. 2 as example. The absorption observed at 200–300 nm attri-
bute to ligand centered charge transfer included
p ?
p⁄ transitions
of phenanthroline and benzene chromophore of phenylcyanamide
ligands. In spite of other cyanamide complexes with transition
metals such as [Ru(NH3)5(2,3-Cl2Hpcyd)]2+ [20], [(bpy)2Cu((4-
Cl)pcyd)][PF6] [21], cis-[Co(bpy)2(2,4-Me2pcyd)2]PF6 [23], that
show intensive LMCT and MLCT bands in visible region, there were
no observable transitions in this region for the prepared com-
plexes. The effect of coordination of the metal center on the phe-
nanthroline transitions was the stabilization of the p⁄ orbitals
and the partial shifting of its absorptions to lower energies, but
the phenyl cyanamide ligand transitions showed unusual blue
shifts after complexation. These complexes did not display f–f tran-
sition bands because the lanthanum(III) ion did not have any elec-
trons in its f orbitals.
2235 cmꢁ1 in the spectra of the free ligands assigned to
m(NCN)
shifted to lower frequencies upon the complexation of Lanthanum
by 130–135 cmꢁ1. The C@N stretching bands of phen in [La(phen)3-
Cl3.OH2] changed when the cyanamide ligands coordinated to the
metal ion. The absorption bands at 1513, 1420 cmꢁ1 (C@N of phen)
shifted to lower wave numbers upon complexation with cyana-
mide groups [28]. No vibrational mode was observed at the water
stretching region, thus it is proposed that these complexes do not
have any coordinated water in their coordination spheres.
All resonances in the 1H NMR spectra of the (1–5) complexes
were assigned on the basis of their intensities, line width and
chemical shifts at room temperature. The NMR spectrum of com-
plex (1) consisted of four relatively broad resonances. The phen
signals of D2O solution of complex (1) were found to shift to minor
higher fields compared with free phen [36] which is in opposition
with the reported characteristics of similar La complexes [14,36].
The NMR signals of phen protons in (2–5) appeared as four signals
in the range of 7.49–9.47 ppm. The signals of H2 and H4 protons of
phen have shifted to down field but the signals of H3 and H5 of
phen have shifted to up field and all of the signals have slightly
broadened compared with the free ligand.
The proton chemical shifts of pcyd ligands mostly occurred in
the 6–7 ppm range [27]. The protons of pcyd ligand of complex
(2) were obtained as one broad signal at 6.85–7.12 ppm. The
NMR signals of pcyd protons in (3) showed three signals, two dou-
blets at 6.92 ppm and at 6.43 ppm respectively for H4 and H3 with
2
b
1.5
c
a
1
0.5
0
220 240 260 280 300 320 340 360 380 400
Wavelength/nm
Fig. 2. The UV–Vis absorption spectra of a dichloromethane solution of (a) 2,4-
Cl2pcyd (b) phen, and (c) [La(phen)3(2,4-Cl2pcyd)3].

76
M. Khorasani-Motlagh et al. / Inorganica Chimica Acta 383 (2012) 72–77
3JH3,H4 = 8 Hz and one broad singlet for H6 proton at 6.18 ppm.
Complex (4) showed one broad signal at 6.58–7.10 ppm and one
singlet at 7.31 ppm assigned to the H3 proton. Also, pcyd protons
in (5) showed two broad singlets at 6.84 and 6.06 for H3 and H6
protons, respectively. The 1H NMR data of all species are shown
in Table 4. For example, Fig. 3 shows the 1H NMR spectra of (3)
and (5) in CDCl3 at room temperature.
and three nitrogen atoms from three 2,5-Cl2pcyd which resulted
in nine coordination numbers of the metal center. The average
La–N cyanamide bond (2.543(6) Å) was significantly shorter than
that of La–N phen bonds (2.771(6) Å). The average La–N phen bond
distance (2.771 Å) was slightly longer than the average La–N phen
bond distances in different lanthanum phenanthroline complexes.
For example average La–N phen bond was (2.753(4)) Å for
[La(phen)3(NCS)3] [36], (2.716(4) Å) for [La(DMPA)3phen]2 [37],
(2.746(6) Å) for {[La2(IA)3(phen)2]ꢀ2H2O}n [38], and (2.734(7) Å)
for [La2(APA)6(phen)2(H2O)2](ClO4)6(phen)4ꢀ2H2O [39]. Moreover
La–N band distances were longer than those in [Pr(phen)2Cl3ꢀOH2]
(2.665 Å) [28]. This is in accord with the anticipated ‘‘lanthanide
contraction’’ when progressing from lanthanum to praseodymium
[36].
3.2. Crystal structure of [La(phen)3(2,5-Cl2pcyd)3]ꢀCH2Cl2
[La(phen)3(2,5-Cl2pcyd)3]ꢀCH2Cl2 was crystallized in the mono-
clinic system with the C2/c space group. As shown in Fig. 1, this
complex is mononuclear. Lanthanum atom was coordinated
through six nitrogen atoms from three phenanthroline ligands
Fig. 3. 1H NMR spectra of (a) [La(phen)3(2,5-Cl2pcyd)3] and (b) [La(phen)3(2,4,5-Cl3pcyd)3] in CDCl3n CDCl3.

M. Khorasani-Motlagh et al. / Inorganica Chimica Acta 383 (2012) 72–77
77
plexes such as [FeIII(OEP)(pcyd)] [41] and [FeIII(OEP)(2,4-Me2pcyd)]
[43].
C
N
N
C
N
N
Acknowledgment
We thank the University of Sistan and Baluchestan (USB) for
financial support.
II
I
Scheme 2. Resonance structures of phenylcyanamide anionic ligand.
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