High-coordinated lanthanum(III) complexes with new mono-and bidentate phosphoryl donors; Spectroscopic and structural aspects

Article abstract of DOI:10.1016/j.ica.2010.03.064

Monodentate and bidentate ligands PhNHP(O)(NC₄H ₈O)₂ (1) and PhC(O)NHP(O)(NH(tert-C₄H ₉))₂ (2) were used to prepare new 7, 9 and 10-coordinated lanthanum(III) complexes; La(1)₂Cl

Full text of DOI:10.1016/j.ica.2010.03.064

Inorganica Chimica Acta 363 (2010) 2318–2324
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Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
High-coordinated lanthanum(III) complexes with new mono- and bidentate
phosphoryl donors; spectroscopic and structural aspects
*
Khodayar Gholivand , Hamid Reza Mahzouni, Mehrdad Pourayoubi, Shadi Amiri
Department of Chemistry, Tarbiat Modares University, P.O. Box 14115-175, Tehran, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
Monodentate and bidentate ligands PhNHP(O)(NC4H8O)2 (1) and PhC(O)NHP(O)(NH(tert-C4H9))2 (2) were
Received 7 December 2009
Received in revised form 20 March 2010
Accepted 24 March 2010
used to prepare new 7,
9 and 10-coordinated lanthanum(III) complexes; La(1)2Cl3(H2O)2 (3),
La(1)2(NO3)3H2O.La(1)2(NO3)3CH3CN (4) and La(2)2(NO3)3 (5), respectively. Crystallization of compound
2 in CH3OH:CH3CN leads to one conformer in contrast to the crystallization result from CHCl3:n-C7H16
(two conformers). Compound 4 contains two independent nine-coordinated La(III) complexes that are
Available online 29 March 2010
different in the solvated molecules (H2O and CH3CN). Some structural and electronic perturbations in
Keywords:
Bidentate
Counter ion
Lanthanum(III) complex
Phosphoryl
2
coordinated ligand were occurred upon complexation, that are confirmed by increase of JPH
,
3JPH and
6JPH coupling constants from the free ligand 1 to complexes 3 and 4. The steric repulsions in the first coor-
dination sphere of La3+ ion, metal–ligand (M–L) binding strength and P@O stretching frequency are very
influenced by changing the counter ion from Clꢀ to NO3ꢀ. Comparing the X-ray crystallography data of
free ligand 2 with bis-chelated complex 5, it is found that the phosphoryl group is more reactive than car-
X-ray crystallography
Hydrogen bonding
bonyl counterpart. A blue shift of the m(N–H) vibration is observed in line with the weakening of the
hydrogen bond from N–HꢁꢁꢁOPhosphoryl in 1 to N–HꢁꢁꢁCl in 3. Three dimensional butterfly-shape structures
are seen in the unit cell of complex 3, which are produced by OWater–HꢁꢁꢁOMorpholine hydrogen bonds.
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
organophosphorus, they can be considered as efficient complexant
agents for lanthanide [33]. Thus, in the present study, two new li-
Lately, a great intense of researches have been focused on the
chemistry of phosphoryl–lanthanide complexes because of their
importance in biological sciences [1–4], luminescent systems [5–
8] and nuclear waste reprocessing [9,10]. The highly oxophilic nat-
ure of lanthanides makes they interact strongly with phosphoryl
donors [11]. Up to now, various bidentate RC(O)CH2P(O)(R0)2 and
monodentate (R)3PO ligands have been extensively used to extract
and separate of lanthanides and actinides [12–16]. Furthermore,
some of the organophosphorus–lanthanide(III) [17–22] and com-
plexes of Ce, Eu and Sm with RC(O)NHP(O)(NHR0)2 ligands have
been reported [23–25]. Also, the structural, electronic and energy
features of lanthanides and actinides complexes of organophos-
phorus ligands have been theoretically investigated [26–32]. To
our knowledge, there are a few reports (experimental or theoreti-
cal) of high coordinated La(III)-[P(O)(RC(O)NH)(NHR)2] and La(III)-
P(O)(NHR)(NHR0)2 complexes. Using the quantum mechanical cal-
culations we have already shown that cation affinity of phosphora-
mides is very close to that of organophosphorus ligands from the
energy point of view. Taking into account that the synthesis path-
way of phosphoramides is relatively inexpensive with respect to
gands, N-phenyl-N0,N00-bis(morpholinyl) phosphoric triamide (1)
and N-benzoyl-N0,N00-bis(tert-butyl) phosphoric triamide (2) were
used to prepare the 7-, 9- and 10-coordinated La(III) complexes
3–5 (Schemes 1 and 2). To achieve ligands with a good electron
donating ability of phosphoryl group, we have selected both of ali-
phatic and aromatic substituents. To reach more hydrogen bonds
in the solid state, the morpholine rings were selected as amine sub-
stituent in 1. The electronic distribution and geometry of atoms in
X–HꢁꢁꢁY systems (X and Y are electronegative atoms) affect the
strength of the hydrogen bond and also of the X–H bond [34,35].
Based on these theories, the hydrogen bonds in free ligands and
complexes were compared. The phosphorus–hydrogen coupling
constants, the stretching frequencies of the N–H, P@O and C@O
bonds and the M–O, P@O and P–N bond lengths were compared
to realize the structural reorganizations of the ligands upon com-
plex formation.
2. Experimental
2.1. X-ray crystallography
Single crystals of compounds 3–5 obtained from a mixture of
CH3OH:CH3CN (with ratio 1:4) at room temperature. X-ray data
* Corresponding author. Tel.: +98 21 82883443; fax: +98 21 8006544.
E-mail address: gholi_kh@modares.ac.ir (K. Gholivand).
0020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2010.03.064

K. Gholivand et al. / Inorganica Chimica Acta 363 (2010) 2318–2324
2319
O
P
2.2. Instrumentation
La(NO3)3.6H2O
in Acetonitrile
LaCl3.7H2O
N
O
NH
1H, 13C and 31P spectra were recorded on a Bruker Avance DRS
500 spectrometer. 1H and 13C chemical shifts were determined rel-
ative to internal TMS, 31P chemical shifts relative to 85% H3PO4 as
external standard. Infrared (IR) spectra were recorded on a Shima-
dzu model IR-60 spectrometer using KBr pellets. Elemental analy-
sis was performed using a Heraeus CHN-O-RAPID apparatus.
in Acetonitrile
2
(1)
NH
HN
O
LaCl3(H2O)2
(X)(NO3)3La
P
O
P
N
N
X= H2O
(4a)
(3)
O
O
= CH3CN (4b)
2
2
2
2.3. Preparation of ligand P(O)(PhNH)(NC4H8O)2; (1)
2
Scheme 1. Synthesis pathway of complexes 3 and 4 from the free ligand 1.
To a stirred solution of N-phenyl-phosphoramidic dichloride
(1 mmol) in dry acetonitrile (35 ml), a solution of 4 mmol morpho-
line was added dropwise at ꢀ5ꢀC. After 10 h stirring, the solvent
was evaporated under vacuum and the white powder was washed
of compounds 1 and 5 were collected on CAD4 Enraf-Nonius and
for compounds 3 and 4 on a Bruker SMART APEX2 CCD area detector
single crystal diffractometer with graphite monochromated Mo K
with distilled water and recrystallized from
a mixture of
a
-
CH3OH:CHCl3 (1:3). Yield 75%, M.p. 181°C, Anal. Calc. for
C14H22N3O3Pꢁ0.25CHCl3: C, 50.16; H, 6.57; N, 12.32. Found: C,
50.48; H, 6.65; N, 12.21%. 1H NMR (CDCl3, 500.13 MHz, 298 K):
radiation (k = 0.71073 Å). The structures were refined with SHELXL
97 [36] by full matrix least squares on F2. The crystallographic data
and the details of the X-ray analysis of the compounds 1 and 3–5
are summarized in Table 1.
2
d = 3.18 (m, 8H, CH2), 3.60 (m, 8H, CH2), 5.11 (d, JPH = 8.1 Hz, 1H,
3
3
NH), 6.98 (t, JHH = 7.6 Hz, 1H, Ar–H), 7.08 (d, JHH = 7.6 Hz, 2H,
NHC(CH3)3
O
P
O
O
O
P
NHC(CH3)3
NH
La(NO3)3.6H2O
in Acetonitrile
(NO3)3La
NHC(CH3)3
NHC(CH3)3
N
2
H
(5)
(2)
2
Scheme 2. Synthesis pathway of complex 5 from 2.
Table 1
Crystallographic data for compounds 1 and 3–5.
1 0.25CHCl3
3
[4aꢁ4b].H2O
5
Empirical formula
Formula weight
T (K)
C14H22N3O3P.0.25(CHCl3)
341.16
293(2)
C28H48Cl3LaN6O8P2
903.92
100(2)
C58H95La2N19O32P4
1972.23
100(2)
C30H52LaN9O13P2
947.66
293(2)
k (Å)
0.71073
0.71073
0.71073
0.71073
Crystal system
Space group
a (Å)
b (Å)
c (Å)
monoclinic
P21/c
9.6943(19)
10.339(2)
19.501(4)
90
orthorhombic
Fdd2
14.4045(18)
39.958(3)
12.9802(9)
90
triclinic
P1
10.8328(9)
16.3636(14)
23.5928(19
99.816(2)
monoclinic
P21/c
12.066(6)
24.273(12)
15.530(6)
90
ꢁ
a
(°)
b (°)
104.05(3)
90
1896.1(7)
90
90
100.440(2)
94.052(2)
4030.4(6)
101.53(3)
90
4457(4)
c
(°)
V (Å3)
7471.2(12)
Z
4
8
2
4
Calculated density (g cmꢀ3
)
1.195
0.264
722
1.607
1.497
3680
1.625
1.220
2012
1.412
1.095
1944
Absorption coefficient (mmꢀ1
F(0 0 0)
)
Crystal size (mm)
h range for data collection (°)
Limiting indices
0.30 ꢂ 0.20 ꢂ 0.10
0.30 ꢂ 0.25 ꢂ 0.20
0.150 ꢂ 0.080 ꢂ 0.020
1.27–28.00
ꢀ14 6 h 6 14
ꢀ21 6 k 6 21
ꢀ24 6 l 6 31
33627
0.35 ꢂ 0.25 ꢂ 0.04
2.17–25.97
2.04–27.98
1.58–26.97
0 6 h 6 11
ꢀ18 6 h 6 18
ꢀ45 6 k 6 52
ꢀ12 6 l 6 17
9929
3746[R(int) = 0.0290]
full-matrix least-squares on
F2
0 6 h 6 15
0 6 k 6 12
0 6 k 6 30
ꢀ24 6 l 6 23
ꢀ19 6 l 6 19
Reflections collected
Independent reflection
Refinement method
3825
9420
3609[R(int) = 0.0701]
full-matrix least-squares on
F2
19260[R(int) = 0.0768]
9042[R(int) = 0.0882]
full-matrix least-squares on
F2
full-matrix least-squares on
F2
Completeness to theta (%)
Data/restraints/parameters
Goodness-of-fit (GOF) on F2
Final R indices
97.5
3609/9/225
1.021
R1 = 0.0711, wR2 = 0.1479
R1 = 0.1490, wR2 = 0.1724
0.727 and ꢀ0.356
99.8
3746/1/218
1.000
R1 = 0.0204, wR2 = 0.0418
R1 = 0.0221, wR2 = 0.0424
0.478 and ꢀ0.481
99.0
19260/0/947
1.008
R1 = 0.0795, wR2 = 0.1738
R1 = 0.1423, wR2 = 0.2018
2.617 and ꢀ1.304
93.1
9042/0/496
1.089
R1 = 0.0863, wR2 = 0.1691
R1 = 0.2048, wR2 = 0.2072
1.778 and ꢀ1.582
R indices (all data)
Largest difference in peak and hole
(e Åꢀ3
)

2320
K. Gholivand et al. / Inorganica Chimica Acta 363 (2010) 2318–2324
Ar–H), 7.23 (t, 3JHH = 7.6 Hz, 2H, Ar–H) ppm. 13C{1H} NMR (DMSO-
d = 11.59 (s) ppm. IR (KBr, cmꢀ1): 3360, 3300, 2845, 1593, 1485,
1441, 1381, 1296, 1259, 1131, 1109, 1021, 967, 943, 749, 690, 498.
3
d6, 125.76 MHz, 298 K): d = 44.57 (s, CH2), 66.63 (d, JPC = 5.5 Hz,
3
CH2), 117.90 (d, JPC = 6.4 Hz, Cortho), 121.48 (s), 128.79 (s), 139.82
(s) ppm. 31P{1H} NMR (DMSO-d6, 202.46 MHz, 298 K): d = 10.34
(s) ppm. IR (KBr, cmꢀ1): 3420, 3198, 2895, 1592, 1488, 1438,
1289, 1253, 1192, 1127, 1087, 1020, 963, 930, 748, 689, 500.
2.8. Data for La(2)2(NO3)3; (5)
Yield 68%. M.p. 265 °C, Anal. Calc. for C30H52LaN9O13P2: C, 38.02;
H, 5.53; N, 13.30. Found: C, 38.19; H, 5.61; N, 13.22%. 1H NMR
(DMSO-d6, 500.13 MHz, 298 K): d = 1.32 (s, 36 H, 4 tBu), 7.48 (t,
3JHH = 7.8 Hz, 2 H), 7.59 (t, 3JHH = 7.4 Hz, 4 H), 7.89 (d, 3JHH = 7.3 Hz,
4 H) ppm. 13C{1H} NMR (DMSO-d6, 125.76 MHz, 298 K): d = 29.84
2.4. Preparation of ligand P(O)(PhC(O)NH)(NH(tert-C4H9))2; (2)
N-Benzoyl, N0,N00-bis(tert-butyl) phosphoric triamide (2) was
prepared similar to the reported procedure [37,38] and recrystal-
lized in CH3OH:CH3CN (1:3). Yield 80%. Decom. point. 98 °C, Anal.
Calc. for C15H26N3O2P: C, 57.86; H, 8.42; N, 13.50. Found: C,
57.72; H, 8.51; N, 13.41%. 1H NMR (DMSO-d6, 500.13 MHz,
298 K): d = 1.21 (s, 9H, tert-Bu), 1.24 (s, 9H, tBu), 4.00 (d,
3
(d, JPC = 5.0 Hz, CH3), 50.70 (s), 127.26 (s), 127.86 (s), 132.11 (s)
ppm. 31P{1H} NMR (DMSO-d6, 202.46 MHz, 298 K): d = 3.82 (s)
ppm. IR (KBr, cmꢀ1): 3305, 2965, 1617, 1566, 1453, 1386, 1330,
1279, 1225, 1180, 1152, 1020, 925, 892, 833, 788, 664, 561.
3
2JPH =6.6 Hz, 2H, NH), 7.43 (t, JHH = 7.6 Hz, 1H, Ar–H), 7.62 (t,
3JHH = 7.3 Hz, 1H, Ar–H), 7.95 (m, 3H, Ar–H), 9.46 (b, 1H, NH)
3. Results and discussion
ppm. 13C{1H} NMR (DMSO-d6, 125.76 MHz, 298 K): d = 27.11 (s),
3
31.23 (d, JPC = 4.9 Hz), 50.35 (s), 50.92 (s), 127.97 (s), 128.21 (s),
3.1. Spectroscopic investigations
131.82 (s), 168.19 (s, C@O) ppm. 31P{1H} NMR (DMSO-d6,
202.46 MHz, 298 K): d = 4.10 (s) ppm. IR (KBr, cmꢀ1): 3115, 2940,
1634, 1496, 1418, 1387, 1279, 1234, 1009, 957, 534.
Some structural and electronic perturbations are occurred in
the ligand structure upon complexation, due to the polarization ef-
fects and electron donation to the cation. The 31P NMR resonances
of 3 and 4 are shifted downfield with respect to the free ligand 1
(Table 2). This is consistent with an increase of partial positive
charge on phosphorus atom. In 1H NMR, a doublet at 5.11 ppm
(2JPH = 8.1 Hz) corresponds to the amine (aniline) proton in free li-
gand 1. This signal shifts to 7.43 and 7.20 ppm in complexes 3
2.5. General procedure for the preparation of complexes
To a stirred solution of LaCl3ꢁ7H2O or La(NO3)3ꢁ6H2O (1 mmol)
in 10 ml of acetonitrile was added a solution of corresponding li-
gands (2 mmol in 30 ml acetonitrile) at 60 °C. After 3 days stirring
at room temperature, the resulting white solid was filtered. Crys-
tals suitable for X-ray diffraction were obtained from CH3OH/
CH3CN solutions of 3, 4 and 5.
2
(2JPH = 9.7 Hz) and 4 (2JPH = 9.8 Hz), respectively. The JPH coupling
constants increase comparatively from the free ligand 1 to com-
plexes 3 and 4, which is in line with the shortening of the P–N
bonds. In free ligand 1, 1H NMR revealed a triplet signal at 6.98
ppm (3JHH = 7.6 Hz) for the para-position hydrogen atom of aniline
ring, that changes to a triplet of doublet signal at 6.79 ppm
2.6. Data for La(1)2Cl3(H2O)2; (3)
6
3
(3JHH = 7.7 Hz, JPH = 1.0 Hz) in complex 3. The JPH coupling con-
stants are 2.0 and 4.3 Hz for hydrogen atoms in morpholine ring
of complexes 3 and 4, respectively. It should be noted that the
phosphorus-hydrogen spin coupling depends on the distance and
dihedral angle between two coupled atoms [39]. Herein, the suit-
able distance and dihedral angle between phosphorus and hydro-
Yield 65%, M.p. 192 °C, Anal. Calc. for C28H48Cl3LaN6O8P2: C,
37.21; H, 5.35; N, 9.30. Found: C, 37.05; H, 5.43; N, 9.39%. 1H
NMR (DMSO-d6, 500.13 MHz, 298 K): d = 3.12 (m, 16H, CH2), 3.44
3
6
(m, 16H, CH2), 6.79 (m, JHH = 7.7 Hz, JPH = 1.0 Hz, 2H, Ar–H),
7.16 (m, 8H, Ar–H), 7.43 (d, JPH = 9.7 Hz, 2H, NH) ppm. 13C{1H}
2
NMR (DMSO-d6, 125.76 MHz, 298 K): d = 44.34 (s), 66.43 (d,
3
3JPC = 5.9 Hz), 117.79 (d, JPC = 6.6 Hz), 120.05 (s), 128.56 (s),
6
3
gen atoms cause JPH and JPH coupling constants in complexes 3
and 4, which are not appeared in free ligand 1.
142.35 (s) ppm. 31P{1H} NMR (DMSO-d6, 202.46 MHz, 298 K):
d = 11.60 (s) ppm. IR (KBr, cmꢀ1): 3375, 3220, 2835, 1611, 1480,
1353, 1257, 1228, 1151, 1102, 1019, 967, 936, 834, 753, 686,
565, 502.
Crystallization of compound 2 in various solvents leads to dif-
ferent results. The NMR spectra and X-ray crystallography have
corroborated that the crystallization of this compound in a mixture
of CHCl3 and n-C7H16 produces two conformers in solution and so-
lid state [38]. Herein, only one conformer of ligand 2 obtained by
using the solvents with higher polarity (i.e., CH3OH/CH3CN), that
is confirmed by the appearance of one signal at 4.10 ppm in
31P{1H} NMR spectrum. But, this conformer contains two unequal
tert-butyl groups. 1H NMR reveals two separated signal (1.21 and
1.24 ppm) for two tert-butyl groups. 13C NMR spectrum indicates
two different signals for tert-carbon atoms (50.92 and
50.35 ppm) and two signals for the methyl carbon atoms (singlet
2.7. Data for [La(1)2(NO3)3H2O.La(1)2(NO3)3CH3CN].H2O; (4a.4b.H2O)
Yield 55%. M.p. 165 °C, Anal. Calc. for C58H95La2N19O32P4: C,
35.32; H, 4.85; N, 13.50. Found: C, 35.49; H, 4.91; N, 13.66%. 1H
NMR (DMSO-d6, 500.13 MHz, 298 K): d = 2.05 (s, 3H, CH3), 3.01
(m, 32H, CH2), 3.45 (m, 32H, CH2), 5.01 (b, H2O), 6.81 (m,
2
3JHH = 6.8 Hz, 4H), 7.15 (m, 16H), 7.20 (d, JPH = 9.8 Hz, 4H, NH)
ppm. 13C{1H} NMR (DMSO-d6, 125.76 MHz, 298 K): d = 43.31 (s),
3
3
3
65.36 (d, JPC = 5.8 Hz), 116.74 (d, JPC = 6.9 Hz), 119.09 (s), 127.56
at 27.11 and doublet, JPC = 4.9 Hz, at 31.23 ppm) in 2. These indi-
(s), 141.17 (s) ppm. 31P{1H} NMR (DMSO-d6, 202.46 MHz, 298 K):
cate that the two tert-butyl moieties have different orientation and
Table 2
Spectroscopic data of compounds 1–5.
2,3
3,6
Compound
d (31P)(ppm)
2JPH (Hz)
(
J
)
(Hz)
J
(Hz)
PH
mP@O (cmꢀ1
)
mc@O (cmꢀ1
)
mN–H (cmꢀ1
)
PC aliphatic
1
2
3
4
5
10.34
4.10
11.60
11.59
3.82
8.1
6.6
9.7
9.8
0.0, 5.5
0.0, 4.9
0.0, 5.9
0.0, 5.8
0.0, 5.0
0.0, 0.0
1192
1234
1151
1131
1225
3198
3115
3220
3300
3305
1634
2.0, 1.0
4.3, 0.0
1617

K. Gholivand et al. / Inorganica Chimica Acta 363 (2010) 2318–2324
2321
Fig. 1. Thermal ellipsoid plot of 1. Ellipsoids are shown at 50% probability.
Fig. 2. ORTEP diagram (at the 50% probability level) of 3, with the H atoms omitted
for clarity.
they are not equivalent. The 1H and 13C NMR spectra of 5 indicate
that the non equivalency of two tert-butyl moieties has been re-
moved after complexation. The 1H NMR spectrum of complex 5
shows one singlet peak at 1.32 ppm for tert-butyl protons. Corre-
sponding 13C NMR spectrum indicates one signal at 50.70 ppm
for the tert-carbon atoms and a doublet at 29.84 ppm (3JPC = 5.0 Hz)
for the methyl carbon atoms.
3 and 4 is stronger than that in 5. This may be attributed to the
weak M–L interaction in high coordinated complex 5.
The direct relationship is observed between the N–H stretching
frequency (
2
m
N–H) and JPH coupling constant in the order of
2 < 1 < 3 < 4 (see Table 2). It seems that the P–N bond strengthen-
ing affects the N–H vibrational frequency. It should be noted that
the hydrogen bond gives rise to increase the X–H bond length
(red shift) in X–HꢁꢁꢁY system. This interaction leads to increase
the X–H band intensity [40]. Here, the N–H band appears at
3198 cmꢀ1 (sharp) in free ligand 1 and at 3220 cmꢀ1 (medium)
in complex 3. As a result, the N–H band shifts toward higher fre-
quencies by weakening of the hydrogen bond from N–HꢁꢁꢁOP in 1
to N–HꢁꢁꢁCl in 3. The wide bands at 3375 and 3360 cmꢀ1 in com-
plexes 3 and 4 may be related to the O–H stretching frequencies.
A significant decreasing of the mP@O is observed by complexation
of these phosphoryl containing ligands with metal ions. The IR
spectra show that the P@O stretching frequency shifts consider-
ably from 1192 cmꢀ1 (in free ligand 1) to 1151 and 1131 cmꢀ1 in
complexes 3 and 4, respectively. But these shifts are relatively
smaller in complex 5 in which the mP@O and mC@O are decreased
about 9 and 17 cmꢀ1 when compared with free ligand 2. The large
shifts in the position of P@O stretching frequency from the free li-
gand 1 to complexes 3 and 4, confirm that the La–OP interaction in
Fig. 3. Representation of three molecules 4a, 4b and H2O in unit cell of compound 4. The hydrogen atoms are shown only for H2O.

2322
K. Gholivand et al. / Inorganica Chimica Acta 363 (2010) 2318–2324
3.2. Structural studies using X-ray crystallography
3.2.1. Structural comparison between the free ligands and coordinated
ones
The molecular structure of compounds 1, 3, 4 and 5 are shown
in Figs. 1–5 and selected structural parameters are given in Supple-
mentary materials (Table S1). Upon complexation, the P@O bond
length of free ligand 1 increases from 1.473(3) Å to 1.493(17 Å in
3, 1.497(6) Å in 4a and 1.492(7) Å in 4b. Whereas, the mean P–N
bond lengths decreases for example from P1–N3 = 1.649(3) Å in
free ligand 1 to 1.642(2) Å for P1–N1 in 3 and to 1.635(8) Å for
P2–N9 in 4a. These observations represent the increasing of the
P–N bond order. Lengthening of the P@O bond may be attributed
to the polarization of phosphoryl group in the electrostatic field
of metal cation, which has been suggested by Berny et al. [26]. Sim-
ilarly, it can be considered that the partial charges on the phospho-
rus and nitrogen atoms increase because of the P@O bond
polarization by metal ion (Scheme 3). Thus, the electrostatic inter-
action increases between phosphorus and nitrogen atoms. This po-
Fig. 5. View of the structure of 5. Ellipsoids are shown at the 50% probability level.
Hydrogen atoms are omitted for clarity and amine groups reduced to their N atoms.
lar bond overlaps with P–N
r bond [41], which may explain the
shortening of the P–N bond in complex.
H
H
..
R
..
N
R
N
+
δ
+
P
O
Mn+
δ
P
M
+
O
δ
-
Scheme 3. Schematic representation of electronic reorganization in coordinated
ligand.
The C@O and P@O groups adopt anti configuration as a result of
the dipole–dipole repulsion. For instance, the O–P–N–Ccarbonyl tor-
sion angles are ꢀ174.8(2)° and ꢀ176.6(2)° for two conformers in 2
[38]. These torsion angles vary to 44.1(10)° and 49.1(9)° for two
coordinated ligands in 5. The phosphoryl and carbonyl functional
groups with torsion angles (O2–C1ꢁꢁꢁP1–O1) and (O4–C16ꢁꢁꢁP2–
O3) take the nearly syn configuration in complex 5. These changes
are needed to bis-chelation of free ligand 2.
The unit cell of complex 4 includes three independent mole-
cules 4a, 4b and a free water molecule (Figs. 3 and 4). Moreover,
one water molecule (O-donor) and acetonitrile (N-donor) are coor-
dinated to the metal cation in 4a and 4b, respectively. This causes a
difference in the La–OP distances in 4a and 4b. For instance, the
La1–O1 and La1–O2 are 2.427(6) Å in molecule 4a that differ from
La10–O10 (2.399(6) Å) and La10–O20 (2.417(6) Å) in molecule 4b.
Whereas, the ON atoms are negatively charged in nitrate counter
ion, the LaꢁꢁꢁONitrate interaction is expected to be stronger than
LaꢁꢁꢁOP in 4a and 4b. But the mean La–ONitrate distances is longer
than the La–OP one in 4a and 4b (Table 3), probably due to the ste-
ric hindrance which is created by bis-chelation of the nitrate coun-
ter ion in the first shell of La3+
.
3.2.2. Comparison between the coordination ability of the P@O and
C@O functional groups
The monodentate ligand 1 is coordinated to the La3+ cation as an
O-donor in structures 3 and 4, while ligand 2 (O,O0-donor) chelates
the metal cation via P@O and C@O groups in structure 5. Whereas,
the phosphoryl group is more polarizable than the carbonyl group,
the increasing of negative charge on the OP atom is approximately
two times more than that of OC in complexation ð
D
dꢀðOC
<
D
dꢀðOPÞ when
D
dꢀ ¼ dꢀðOÞcomplex ꢀ dꢀðOÞfree ligandÞ[31]. In the
Fig. 4. Coordination structure in a) 4a and b) 4b. All hydrogen atoms were omitted
for clarity and the amine groups reduced to their N atoms. Thermal ellipsoids are
drawn at the 50% probability level.
bis-chelated complex 5, the La–OP distances of 2.438(7) and
2.427(7) Å are relatively shorter than the La–OC distances

K. Gholivand et al. / Inorganica Chimica Acta 363 (2010) 2318–2324
2323
(2.553(7) and 2.587(7) Å). Therefore, it can be concluded that the
La3+ ion interacts more strongly with the P@O functional group
than the C@O counterpart.
system is followed by electron density transfer from Y to the
*
r
(X–H) antibonding orbital, which results in weakening of the
X–H bond and red shift of the X–H vibrational frequency [34]. Sim-
*
r (O–H) orbital is a better electron
ilarly, it can be said that the
*
acceptor than the
r (N–H) orbital leading to the stronger OW–
3.2.3. The effect of monodentate and bidentate counter ions on the La–
OP distance
HꢁꢁꢁOM (OM stands for OMorpholine) hydrogen bond than the N–HꢁꢁꢁCl
in complex 3. Moreover, the hydrogen bonds of type N–HꢁꢁꢁOP
(dNꢁꢁꢁO = 2.938(5) Å and \N–H–O = 169°) in crystal lattice of free li-
The quantum mechanical studies on (R3P@O)nꢁꢁꢁLn(X)3 com-
plexes (X= Clꢀ and NO3ꢀ, n = 1, 2) have corroborated that the Ln–
OP distance increases from the chloride to the nitrate complexes
due to the increased steric crowding around the cation with the
bidentate counter ions [31]. Herein, the La–OP distance of
2.397(2) Å in chloride complex (3) increases to 2.399(6),
2.417(6), 2.427(6) and 2.427(6) Å (for La1–O1, La1–O2, La10-O10
and La10–O20, respectively) in nitrate complex (4). In the gas phase,
the P@O bond in chloride complex is expected to be longer than
that in nitrate complex as a function of M–OP bond strength [31].
However, in the solid state, it was found that the P@O bond in chlo-
ride complex is shorter than that in nitrate one, considering the
P@O band in IR spectra (1151 vs. 1131 cmꢀ1). The theoretical
(gas phase) and experimental (solid phase) results may differ, since
the geometry of molecule may be influenced by packing and crys-
tal field in the solid state. Unlike the gas phase, hydrogen bonds are
formed in the solid phase. The nitrate counter ions are more in-
volved in hydrogen bonds with respect to the chloride counter ions
(see Section 3.2.4). This leads to remain a higher positive charge on
La3+ cation due to a decreased electron density transfer from the
nitrate to the La3+ cation. Consequently, the P@O bond may be
more polarized and attenuated in nitrate complex.
gand
1
are replaced by weak N–HꢁꢁꢁCl hydrogen bond
(dNꢁꢁꢁCl = 3.388(2) Å and \N–H–Cl = 150°) in complex 3, which is
in agreement with increasing of the N–H stretching frequency from
1 to 3 in IR spectra. Another feature in complex 3 is the difference
between LaꢁꢁꢁCl(1) and LaꢁꢁꢁCl(2) distances, dLa–Cl(1 < dLa–Cl(2). This
seems to be related to the sharing of Cl(1) and Cl(2) ions in differ-
ent C–HꢁꢁꢁCl(1) and N–HꢁꢁꢁCl(2) hydrogen bonds. Furthermore, the
Ow–HꢁꢁꢁOM hydrogen bonds between the hydrogen atoms of coor-
dinated water molecules and oxygen of morpholine ring have
formed in the complex 3. These hydrogen bonds create a three-
dimensional (3D) network which seems as butterfly-arrays along
the a-axis of unit cell in complex 3 (Fig. 6). Various hydrogen bonds
of Ow–HꢁꢁꢁOw, Ow–HꢁꢁꢁOM and N–HꢁꢁꢁON types make 3D framework
in the crystal lattice of complex 4. Comparison between the do-
nor-acceptor distances in the complexes 3 and 4 shows that the ni-
trate counter ions are more contributed in hydrogen bonding than
chloride counter ions (Table S2). This may have some effects on the
M-L interaction as a result of decreasing electron density transfer
from nitrate group to the La3+ cation.
4. Conclusions
3.2.4. Hydrogen bonding
The data of hydrogen bonds are represented in Supplementary
materials, Table S2. Co-crystallization of solvent (CHCl3) molecule
was occurred in the structure of free ligand 1 via O(1)ꢁꢁꢁCl(2) elec-
trostatic interaction. The hydrogen bond of N–HꢁꢁꢁOP type is an-
other feature in structure 1. The hydrogen bond in the X–HꢁꢁꢁY
The monodentate O-donor P(O)(PhNH)(NC4H8O)2 and bidentate
O,O0-donor P(O)(PhC(O)NH)(NH(tert-C4H9))2 were prepared and
used to synthesis high-coordinated lanthanum(III) chloride and ni-
trate complexes. It is found that the polarity of solvent influences
the crystalline sample. Coordination of the ligand is followed by
a number of structural perturbations such as the changes in the
bond lengths and bond angles, which are confirmed by spectro-
Table 3
2
6
scopic evidences. The JPH,
3JPH and JPH coupling constants in-
The mean values of La–O distance (d; Å) for compounds 3–5.
creased significantly upon complexation. X-ray crystallography
confirmed that the La3+ ion interacts more strongly with phos-
phoryl group than carbonyl counterpart. The experimental obser-
vations in the solid phase were fairly in good agreement with the
gas phase data in the literature for all cases studied here, except
for polarization of P@O in nitrate and chloride complexes. Unlike
the gas phase, the P@O bond becomes more polarized in the nitrate
Parameters
Compound
3
4a
4b
5
d(La–OPhosphoryl
)
2.397
2.427
2.409
2.432
2.570
2.651
d(La–OCarbonyl
d(La–ONitrate
d(La–OWater
)
)
)
2.592
2.513
2.603
2.516
Fig. 6. The 3-D view along the a-axis produced by Ow–HꢁꢁꢁOmorpholine hydrogen bonds in 3 (the hydrogen atoms are omitted for clarity).

2324
K. Gholivand et al. / Inorganica Chimica Acta 363 (2010) 2318–2324
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phase.
Acknowledgment
Support of this work by Tarbiat Modares University is gratefully
acknowledged.
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Appendix A. Supplementary material
CCDC 286213, 647432, 678072 and 265236 contain the supple-
mentary crystallographic data for this paper. These data can be ob-
tained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif. Supplementary
data associated with this article can be found, in the online version,
at doi:10.1016/j.ica.2010.03.064.
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