Three-dimensional open-framework neodymium oxalates with Organic Functional Groups Protruding in 12-member channels

Article abstract of DOI:10.1021/ic020197r

Two open-framework neodymium oxalates, [NH₃CH₂CH(NH₃)CH₃] [Nd(C₂O₄)₂(HCOO)]·H₂O (I) and [OC(CH₃)NCH₂- CH(CH₃)NH₃]Nd(C₂ O₄)₂1·H₂O (II), have been synthesized hydrothermally in the presence of 1,2-diaminopropane (1,2-DAP) and formic (I) and acetic (II) acids. The Nd atoms in both these oxalates have 9-fold coordination with respect to the oxygens, with the Nd atom in a distorted monocapped square antiprism coordination in I and in an idealized D_3h triply capped trigonal prism coordination in II. The three-dimensional framework structures of I and II are built up by in-plane linkages between the Nd and the oxalate moieties, forming layers with 12-membered honeycomb-like apertures, pillared by an out-of-plane oxalate unit. The 12-memberd channel in I contains a dangling formate group in addition to the disordered amine molecule, while in II, the channel has N-(2-aminopropyl acetimide) molecules formed by the in situ reaction of 1,2-DAP and acetic acid. The accessibility of the formate and N-(2-aminopropyl acetimide) functional groups in I and II, respectively, uniformly distributed within the channels enables chemical manipulation. Crystal data: I, monoclinic, space group P2₁/c (no. 14), M = 459.5, a = 9.0279(4) A, b = 18.1362(8) A, c = 8.5631(4) A, β 102.735(10)°, V = 1367.56(11) A³, Z = 4, R₁ = 0.0229, wR2 = 0.0599 [1782 observed reflections with > 2σ(/)]; II, triclinic, space group P1 (no. 2), M = 454.5, a = 8.6222(9) A, b = 9.5683(10) A, c = 9.5712(10) A, α = 109.388(2)°, β = 98.508(10)°, γ = 102.361(12)°, V = 706.73(13) A³, Z = 2, R₁ = 0.0446, wR₂ = 0.115 [1730 observed reflections with > 2σ(/)].

Full text of DOI:10.1021/ic020197r

Inorg. Chem. 2002, 41, 4496−4501
Three-Dimensional Open-Framework Neodymium Oxalates with Organic
Functional Groups Protruding in 12-Member Channels
R. Vaidhyanathan, Srinivasan Natarajan, and C. N. R. Rao*
Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for AdVanced Scientific
Research, Jakkur, P.O., Bangalore 560064, India
Received March 12, 2002
Two open-framework neodymium oxalates, [NH CH CH(NH )CH ][Nd(C O ) (HCOO)]‚H O(I) and [OC(CH )NCH -
3
2
3
3
2
4 2
2
3
2
CH(CH )NH ][Nd(C O ) ]‚H O (II), have been synthesized hydrothermally in the presence of 1,2-diaminopropane
3
3
2
4 2
2
(1,2-DAP) and formic (I) and acetic (II) acids. The Nd atoms in both these oxalates have 9-fold coordination with
respect to the oxygens, with the Nd atom in a distorted monocapped square antiprism coordination in I and in an
idealized D triply capped trigonal prism coordination in II. The three-dimensional framework structures of I and II
3h
are built up by in-plane linkages between the Nd and the oxalate moieties, forming layers with 12-membered
honeycomb-like apertures, pillared by an out-of-plane oxalate unit. The 12-memberd channel in I contains a dangling
formate group in addition to the disordered amine molecule, while in II, the channel has N-(2-aminopropyl acetimide)
molecules formed by the in situ reaction of 1,2-DAP and acetic acid. The accessibility of the formate and N-(2-
aminopropyl acetimide) functional groups in I and II, respectively, uniformly distributed within the channels enables
chemical manipulation. Crystal data: I, monoclinic, space group P21/c (no. 14), M ) 459.5, a ) 9.0279(4) Å, b
3
) 18.1362(8) Å, c ) 8.5631(4) Å, â ) 102.735(10)°, V ) 1367.56(11) Å , Z ) 4, R ) 0.0229, wR ) 0.0599
1
2
[1782 observed reflections with I > 2σ(I)]; II, triclinic, space group P1h (no. 2), M ) 454.5, a ) 8.6222(9) Å, b )
3
9.5683(10) Å, c ) 9.5712(10) Å, R ) 109.388(2)°, â ) 98.508(10)°, γ ) 102.361(12)°, V ) 706.73(13) Å , Z
) 2, R ) 0.0446, wR ) 0.115 [1730 observed reflections with I > 2σ(I)].
1
2
Introduction
ligands have also attracted attention as possible building units
of new framework architectures.6,7 Thus, in a phosphonate-
carboxylate of zinc, Stucky and co-workers8 have established
the formation of a new channel structure possessing dangling
organic functional groups. Such compounds are expected to
exhibit novel molecular recognition properties and chemical
reactivity. Synthesis of such structures, however desirable,
poses significant challenges due to the high coordination
tendency and flexibility of the organic functional groups. On
the basis of our experience with the synthesis of open-
The hydrothermal syntheses of silicates and phosphates
with open architectures have been investigated in great detail
for their potential applications in industrially important
processes.1,2 During the last couple of years, the family of
open-framework solids has been extended to a large number
of metal dicarboxylates and other systems.3-5 Multifunctional
* Author to whom correspondence should be addressed. E-mail: cnrrao@
jncasr.ac.in.
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J. M.; Raja, R.; Sankar G.; Bell, R. G. Acc. Chem. Res. 2001, 34,
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Ed. 1999, 38, 3268.
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F.; Ferey, G. J. Mater. Chem. 1998, 8, 2749. (c) Serpaggi, F.;
Luxbacher, T.; Cheetham, A. K.; Ferey, G. J. Solid State Chem. 1999,
145, 580.
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J. Am. Chem. Soc. 1999, 121, 1651. (b) Reineke, T. M.; Eddaoudi,
M.; O′Keeffe, M.; Yaghi, O. M. Angew. Chem., Int. Ed. 1999, 38,
2590.
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1998, 8, 2743. (b) Livage, C.; Egger, C.; Ferey, G. Chem. Mater. 1999,
11, 1546. (c) Kuhlman, R.; Schemek, G. L.; Kolis, J. W. Inorg. Chem.
1999, 38, 194.
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S. J.; Todorov, E.; Cruz, C.; Sevov, S. C. Chem. Commun. 2000, 1213.
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Chem. Commun. 1995, 1051. (b) Drumel, S.; Janvier, P.; Barboux,
P.; Bujoli-Doeuff, M.; Bujoli, B. Inorg. Chem. 1995, 34, 148. (c)
Drumel, S.; Janvier, P.; Barboux, P.; Bujoli-Doeuff, M.; Bujoli, B.
New J. Chem. 1995, 19, 239. (d) Hix, G. B.; Wragg, D. S.; Wright, P.
A.; Morris, R. E. J. Chem. Soc., Dalton Trans. 1998, 3359.
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4496 Inorganic Chemistry, Vol. 41, No. 17, 2002
10.1021/ic020197r CCC: $22.00 © 2002 American Chemical Society
Published on Web 07/31/2002

3-Dimensional Open-Framework Neodymium Oxalates
framework oxalates,9,10 it appeared to us that it may be
possible to obtain new oxalates with functionalized channels
under suitable synthetic conditions. In this effort, we have
been able to isolate two new open-framework oxalates of
neodymium, wherein the carboxylate and amino functional
groups protrude into 12-member channels. The compounds
with the composition [NH3CH2CH(NH3)CH3][Nd(C2O4)2-
(HCOO)]‚H2O (I) and [OC(CH3)NCH2CH(CH3)NH3][Nd-
(C2O4)2]‚H2O (II) were synthesized hydrothermally in the
presence of 1,2-diaminopropane (1,2-DAP). While the
amines in I are disordered, they react with the acetic acid
forming N-(2-aminopropyl acetimide) in II. To our knowl-
edge, both these compounds are new and are described here
for the first time.
Table 1. Powder X-ray Data for I,
[H3NCH2CH(NH3)CH3][Nd(C2O4)2(HCOO)]‚H2O
c
h
K
l
2θobs
∆(2θ)a
dcalc
∆(d)b
Irel
1
1
1
2
1
3
3
2
0
1
3
3
3
4
4
2
1
1
0
6
3
7
3
3
1
0
0
6
2
5
1
0
1
1
1
0
1
1
0
0
1
1
2
0
2
1
3
2
2
1
0
0
2
3
3
4
2
1
3
3
1
11.196
11.702
16.235
16.92
0.004
0.017
0.002
0.009
0.040
0.005
0.021
-0.146
0.122
-0.133
-0.034
-0.096
0.061
0.166
0.048
7.905
7.573
5.46
5.243
4.975
4.889
4.686
4.393
4.27
4.056
3.499
3.411
3.153
3.053
2.826
2.801
2.708
2.69
2.643
2.635
2.481
2.457
2.307
2.264
2.084
2.182
2.119
2.088
2.056
2.005
-0.003
-0.011
-0.001
-0.003
-0.011
-0.001
-0.005
0.032
-0.025
0.025
0.005
0.012
-0.007
-0.017
-0.004
-0.001
-0.001
0.009
0.003
0.004
0.003
77
100
56
44
50
70
62
64
69
54
40
41
42
56
34
40
43
44
48
59
38
35
28
43
35
33
43
54
44
44
0
-1
1
1
0
1
2
2
1
-2
-1
2
-1
-3
-1
2
-3
1
3
1
-3
1
-3
0
3
-3
2
1
4
17.868
18.149
18.957
20.066
20.927
21.778
25.418
26.029
28.367
29.421
31.703
31.967
33.095
33.191
33.881
33.968
36.163
36.637
39.043
39.854
43.327
41.409
42.737
43.508
43.952
45.139
0.013
0.016
Experimental Section
-0.110
-0.033
-0.054
-0.035
0.072
0.006
0.034
-0.084
0.028
0.062
0.170
-0.098
-0.074
Synthesis and Initial Characterization. Compounds I and II
were synthesized hydrothermally in the presence of 1,2-DAP.
Identical starting compositions were employed for both cases, but
with formic and acetic acids in I and II, respectively. Thus, in a
typical synthesis, 1.0Nd(III)(NO3)‚4H2O (0.33 g):6.2DAP (0.43 mL):
6.1H2C2O4‚2H2O (0.63 g):6.2[HCOOH (0.19 mL)(I)/CH3COOH
(0.29 mL)(II)]:67.8H2O were taken and heated in a PTFE-lined
stainless steel autoclave at 180 °C for 132 h. The initial pH in both
cases was close to 5.0. The formic and acetic acids were added
into the synthesis mixture for the possible ligation to the Nd ion to
give the ninth coordination, commonly observed in many of the
earlier reported layered rare-earth oxalates and carboxylates,11,12
and thereby functionalizing the channels. The final product contain-
ing large quantities of rod-shaped crystals was filtered and washed
with deionized water. The yield was about 80% in both cases. The
optical examination, combined with X-ray powder diffraction,
suggests that no other crystalline product was present. The powder
XRD pattern of the powdered single crystals indicated that the
product was a new material and the pattern was entirely consistent
with the structure determined by single-crystal X-ray diffraction.
Typical powder X-ray data for I are presented in Table 1. A least-
squares (LSQ) fit of the powder XRD lines of I gave the following
cell: a ) 9.0065(9) Å, b ) 18.1069(6) Å, c ) 8.5461(9) Å, â )
102.68(8)°, which is in close agreement with that determined by
single-crystal XRD (Table 2).
Thermogravimetric analysis (TGA) was carried out under a flow
of nitrogen (50 mL/min) from room temperature to 700 °C, using
a heating rate of 5 °C min-1. TGA studies indicated a two-step
mass loss in the regions 400-450 and 475-600 °C with total mass
loss corresponding to 48.5% (calcd 51.8%) and 44.3% (calcd
43.7%) respectively for I and II. The final decomposed product,
presumably Nd(OH)CO3 in both cases, was found to be amorphous
by powder XRD. The IR spectroscopy studies of I and II indicated
bands at 1434 cm-1 attributed to CdO stretching for the bonded
oxalate, and the absence of bands in the region 1690-1730 cm-1
-0.004
0.000
-0.002
0.004
-0.002
-0.003
-0.008
0.004
0.004
a 2θobs - 2θcalcd
.
b dobs - dcalcd
.
c 100 × I/Imax
.
Table 2. Crystal Data and Structure Refinement Parameters for
[NH3CH2CH(NH3)CH3][Nd(C2O4)2(HCOO)]‚H2O (I) and
[OC(CH3)NCH2CH(CH3)NH3][Nd(C2O4)2]‚H2O (II)
structural parameter
I
II
chemical formula
Nd1O11C8N2H15
459.5
monoclinic
P2(1)/c (no. 14)
293(2)
Nd1O10C9N2H14
454.5
triclinic
P1h (no. 2)
293(2)
8.6222(9)
9.5683(10)
9.5712(10)
109.388(2)
98.508(10)
102.361(2)
706.73(13)
2
formula mass
cryst sym
space group
T/K
a/Å
b/Å
c/Å
R/deg
â/deg
γ/deg
V/Å3
9.0279(4)
18.1362(8)
8.5631(4)
90.000(1)
102.735(10)
90.000(1)
1367.56(11)
4
Z
λ/Å
0.71073
2.080
3.848
5652/1782
0.71073
2.220
3.738
3031/1730
F
calc/g cm-3
µ/mm-1
no. of measd/
obsd reflns
refinement method
full-matrix least-
squares on |F2|
0.0229,a 0.0599b
full-matrix least-
squares on |F2|
0.0446,a 0.1150b
R1, wR2 [I > 2σ(I)]
2
2
2
a R1 ) ||Fo| - |Fc||/|Fo|. b wR2 ) {[w(Fo - Fc )2]/[w(Fo )2]}1/2. w )
2
1/[σ2(Fo)2 + (aP)2 + bP], P ) [max‚(Fo ,0) + 2(Fc)2]/3, where a ) 0.0267
and b ) 3.6124 for I and a ) 0.10000 and b ) 0.0 for II.
(9) (a) Natarajan, S.; Vaidhyanathan, R.; Rao, C. N. R.; Ayyappan, S.;
Cheetham, A. K. Chem. Mater. 1999, 11, 1633. (b) Vaidhyanathan,
R.; Natarajan, S.; Cheetham, A. K.; Rao, C. N. R. Chem. Mater. 1999,
11, 3636.
(10) (a) Vaidhyanathan, R.; Natarajan, S.; Rao, C. N. R. Chem. Mater.
2001, 13, 185. (b) Vaidhyanathan, R.; Natarajan, S.; Rao, C. N. R. J.
Chem. Soc., Dalton Trans. 2001, 699.
(11) (a) Watanabe, M.; Nagashima, K. J. Inorg. Nucl. Chem. 1971, 33,
3604. (b) McDonald, T. R. R.; Spink, J. M. Acta Crystallogr. 1967,
23, 944.
(12) Bataille, T.; Auffredic, J.-P.; Louer, D. J. Mater. Chem. 2000, 10,
1707 and the references therein.
(O-H vibration of COOH group) is in agreement with the
deprotonated carboxyl group.6a
Single-Crystal Structure Determination. A suitable colorless
rod-shaped single crystal (0.16 × 0.16 × 0.28 mm3 for I and 0.12
× 0.12 × 0.18 mm3 for II) of each compound was selected and
mounted at the tip of a glass fiber with cyanoacrylate (superglue)
adhesive. Single-crystal structure determination by X-ray diffraction
was performed on a Siemens SMART-CCD diffractometer equipped
Inorganic Chemistry, Vol. 41, No. 17, 2002 4497

Vaidhyanathan et al.
Table 3. Selected Bond Distances for Compound I,
[NH3CH2CH(NH3)CH3] [Nd(C2O4)2(HCOO)]‚H2Oa
Table 5. Selected Bond Distances for Compound II,
[OC(CH3)NCH2CH(CH3)NH3][Nd(C2O4)2]‚H2Oa
moiety
distance (Å)
moiety
distance (Å)
moiety
distance (Å)
moiety
distance (Å)
Nd(1)-O(1)
Nd(1)-O(3)
Nd(1)-O(4)
Nd(1)-O(7)
Nd(1)-O(2)
Nd(1)-O(5)
Nd(1)-O(9)
Nd(1)-O(8)#1
Nd(1)-O(6)
O(1)-C(3)
2.462(4)
2.477(4)
2.480(4)
2.488(4)
2.498(4)
2.500(4)
2.511(4)
2.511(4)
2.531(4)
1.251(6)
1.245(6)
1.237(6)
O(5)-C(2)#2
O(6)-C(4)
1.257(6)
1.245(6)
1.249(6)
1.246(6)
1.243(8)
1.255(6)
1.257(6)
1.249(6)
1.562(8)
1.550(10)
1.545(10)
Nd(1)-O(1)
Nd(1)-O(2)
Nd(1)-O(7)
Nd(1)-O(3)
Nd(1)-O(4)
Nd(1)-O(8)
Nd(1)-O(6)
Nd(1)-O(5)
Nd(1)-O(9)
O(1)-C(12)
O(2)-C(14)#1
O(3)-C(13)
O(4)-C(11)#2
2.471(6)
2.461(6)
2.470(8)
2.484(6)
2.496(7)
2.494(7)
2.510(7)
2.521(6)
2.529(7)
1.246(12)
1.261(11)
1.239(11)
1.231(11)
O(5)-C(13)#3
O(6)-C(11)
1.237(11)
1.267(11)
1.21(2)
1.246(11)
1.266(11)
1.261(11)
1.237(11)
1.231(11)
1.55(2)
1.54(2)
1.54(2)
1.53(2)
1.562(11)
O(7)-C(4)#3
O(8)-C(3)
O(7)-C(50)
O(8)-C(14)
O(9)-C(5)
O(9)-C(12)#4
O(2)-C(14)#1
O(5)-C(13)#3
O(4)-C(11)#2
C(12)-C(12)#4
C(14)-C(14)#1
C(13)-C(13)#3
C(11)-C(11)#2
C(50)-C(51)
O(3)-C(1)#4
O(5)-C(2)#4
O(7)-C(4)#3
C(1)-C(2)
C(3)-C(3)#1
C(4)-C(4)#3
O(2)-C(2)
O(4)-C(1)
a Symmetry transformations used to generate equivalent atoms: #1,
-x + 1, -y, -z; #2, x, -y + 1/2, z - 1/2; #3, -x, -y, -z; #4, x, -y + 1/2,
a Symmetry transformations used to generate equivalent atoms: #1, -x,
-y, -z + 1; #2, -x, -y + 1, -z + 1; #3, -x + 1, -y + 1, -z + 1; #4,
-x, -y, -z.
1
z + /2.
Table 4. Selected Bond Angles for Compound I,
[NH3CH2CH(NH3)CH3][Nd(C2O4)2(HCOO)]‚H2Oa
Table 6. Selected Bond Angles for Compound II,
[OC(CH3)NCH2CH(CH3)NH3][Nd(C2O4)2]‚H2Oa
moiety
angle (deg)
moiety
angle (deg)
moiety
angle (deg)
moiety
angle (deg)
O(1)-Nd(1)-O(3)
O(1)-Nd(1)-O(4)
O(3)-Nd(1)-O(4)
O(1)-Nd(1)-O(7)
O(3)-Nd(1)-O(7)
O(4)-Nd(1)-O(7)
O(1)-Nd(1)-O(2)
O(3)-Nd(1)-O(2)
O(4)-Nd(1)-O(2)
O(7)-Nd(1)-O(2)
O(1)-Nd(1)-O(5)
O(3)-Nd(1)-O(5)
O(4)-Nd(1)-O(5)
O(7)-Nd(1)-O(5)
O(2)-Nd(1)-O(5)
O(1)-Nd(1)-O(9)
O(3)-Nd(1)-O(9)
O(4)-Nd(1)-O(9)
O(7)-Nd(1)-O(9)
O(2)-Nd(1)-O(9)
O(5)-Nd(1)-O(9)
O(1)-Nd(1)-O(8)#1
O(3)-Nd(1)-O(8)#1
138.98(12) O(3)-Nd(1)-O(6)
138.42(12) O(4)-Nd(1)-O(6)
75.57(13) O(7)-Nd(1)-O(6)
132.25(12) O(2)-Nd(1)-O(6)
69.91(12) O(5)-Nd(1)-O(6)
72.33(13) O(9)-Nd(1)-O(6)
73.39(12) O(8)#1-Nd(1)-O(6)
126.19(12) C(3)-O(1)-Nd(1)
65.61(12) C(2)-O(2)-Nd(1)
97.41(12)
136.03(13)
64.71(12)
136.40(13)
138.99(13)
72.52(14)
67.81(12)
116.9(3)
O(1)-Nd(1)-O(2)
O(1)-Nd(1)-O(7)
O(2)-Nd(1)-O(7)
O(1)-Nd(1)-O(3)
O(2)-Nd(1)-O(3)
O(7)-Nd(1)-O(3)
O(1)-Nd(1)-O(4)
O(2)-Nd(1)-O(4)
O(7)-Nd(1)-O(4)
O(3)-Nd(1)-O(4)
O(1)-Nd(1)-O(8)
O(2)-Nd(1)-O(8)
O(7)-Nd(1)-O(8)
O(3)-Nd(1)-O(8)
O(4)-Nd(1)-O(8)
O(1)-Nd(1)-O(6)
O(2)-Nd(1)-O(6)
O(7)-Nd(1)-O(6)
O(3)-Nd(1)-O(6)
O(4)-Nd(1)-O(6)
O(8)-Nd(1)-O(6)
O(1)-Nd(1)-O(5)
O(2)-Nd(1)-O(5)
O(7)-Nd(1)-O(5)
O(3)-Nd(1)-O(5)
O(4)-Nd(1)-O(5)
O(8)-Nd(1)-O(5)
O(6)-Nd(1)-O(5)
O(1)-Nd(1)-O(9)
138.3(2)
73.5(2)
79.2(2)
75.7(2)
131.4(2)
82.7(3)
69.4(2)
140.3(2)
139.8(2)
73.7(2)
112.7(2)
65.2(2)
131.7(2)
145.4(2)
78.3(2)
132.1(2)
88.1(2)
142.3(3)
79.4(2)
64.5(2)
70.4(2)
129.8(2)
67.4(2)
72.6(3)
64.2(2)
121.9(2)
117.4(2)
69.7(2)
65.1(2)
O(2)-Nd(1)-O(9)
O(7)-Nd(1)-O(9)
O(3)-Nd(1)-O(9)
O(4)-Nd(1)-O(9)
O(8)-Nd(1)-O(9)
O(6)-Nd(1)-O(9)
O(5)-Nd(1)-O(9)
C(12)-O(1)-Nd(1)
C(14)#1-O(2)-Nd(1)
C(13)-O(3)-Nd(1)
C(11)#2-O(4)-Nd(1)
C(13)#3-O(5)-Nd(1)
C(11)-O(6)-Nd(1)
C(50)-O(7)-Nd(1)
C(14)-O(8)-Nd(1)
C(12)#4-O(9)-Nd(1)
O(1)-C(12)-O(9)#4
O(8)-C(14)-O(2)#1
O(5)#3-C(13)-O(3)
O(4)#2-C(11)-O(6)
O(1)-C(12)-C(12)#4
77.4(2)
73.8(3)
138.6(2)
103.3(2)
67.6(2)
137.8(2)
134.8(2)
120.9(6)
119.9(6)
121.2(6)
120.9(6)
120.3(6)
120.3(6)
137.2(9)
118.6(6)
119.5(6)
126.0(9)
126.5(9)
126.2(9)
125.8(9)
118.3(10)
119.7(3)
125.87(13) C(1)#2-O(3)-Nd(1) 120.2(3)
95.48(12) C(1)-O(4)-Nd(1) 120.2(3)
65.40(12) C(2)#2-O(5)-Nd(1) 119.9(3)
118.3(3)
78.05(14) C(4)-O(6)-Nd(1)
131.01(12) C(4)#3-O(7)-Nd(1) 119.3(3)
71.09(13) C(3)-O(8)-Nd(1)#1 114.9(3)
75.31(13) C(5)-O(9)-Nd(1)
141.04(13) O(4)-C(1)-O(3)#4
86.04(14) O(2)-C(2)-O(5)#4
71.87(14) O(8)-C(3)-O(1)
72.73(14) O(6)-C(4)-O(7)#3
143.80(14) O(9)-C(5)-N(10)
65.28(12) O(4)-C(1)-C(2)
74.11(12) O(3)#4-C(1)-C(2)
134.1(4)
125.3(5)
127.0(5)
126.1(5)
125.6(5)
124.4(7)
117.6(5)
117.1(5)
116.8(5)
116.2(5)
117.5(6)
116.4(6)
117.1(6)
O(9)#4-C(12)-C(12)#4 115.7(11)
O(8)-C(14)-C(14)#1 117.4(10)
O(4)-Nd(1)-O(8)#1 143.78(13) O(2)-C(2)-C(1)
O(7)-Nd(1)-O(8)#1 114.20(13) O(5)#4-C(2)-C(1)
O(2)-Nd(1)-O(8)#1 119.90(13) O(8)-C(3)-C(3)#1
O(5)-Nd(1)-O(8)#1
O(9)-Nd(1)-O(8)#1 130.18(14) O(6)-C(4)-C(4)#3
O(1)-Nd(1)-O(6)
O(2)#1-C(14)-C(14)#1 116.0(10)
O(5)#3-C(13)-C(13)#3 116.6(10)
71.61(13) O(1)-C(3)-C(3)#1
O(3)-C(13)-C(13)#3
117.2(10)
O(4)#2-C(11)-C(11)#2 118.1(10)
O(6)-C(11)-C(11)#2 116.0(11)
72.97(12) O(7)#3-C(4)-C(4)#3 117.4(6)
a Symmetry transformations used to generate equivalent atoms:#1,
-x + 1, -y, -z; #2, x, -y + 1/2, z - 1/2; #3, -x, -y, -z; #4, x, -y + 1/2,
a Symmetry transformations used to generate equivalent atoms: #1, -x,
-y, -z + 1; #2, -x, -y + 1, -z + 1; #3, -x + 1, -y + 1, -z + 1; #4,
-x, -y, -z.
1
z + /2.
with a normal focus, 2.4-kW sealed tube X-ray source (Mo KR
radiation, λ ) 0.71073 Å) operating at 50 kV and 40 mA. A
hemisphere of intensity data was collected at room temperature in
1321 frames with ω scans (width of 0.30° and exposure time of 20
s per frame) in the 2θ range 3-46.6°. Pertinent experimental details
for the structure determinations are presented in Table 2.
The structure was solved by direct methods with SHELXS-8613
and difference Fourier syntheses. An absorption correction based
on symmetry equivalent reflections was applied by using the
SADABS program.14 The amine molecule in I as found to be
disordered and the formate group was attached directly with the
Nd atoms. Similar disorder of the amine molecule, 1,2-DAP, was
observed earlier.15 In the case of II, the amine molecule reacted
with the acetic acid and was bonded with the Nd center. Due to
the disorder of the amine in I and reaction in II, the hydrogen
positions of the amine molecule, though found in the difference
Fourier map, were not incorporated in the final refinement. The
terminal carbonyl oxygen of the formate group in I, found in the
difference Fourier map, has a high degree of positional freedom
and hence was not included in the refinement. In the case of II,
the terminal methyl group of the N-(2-aminopropyl acetimide) was
refined isotropically. The final refinement included atomic positions
for all the atoms and anisotropic thermal parameters for all the non-
(13) Sheldrick, G. M. SHELXS-86, A program for the solution of crystal
structures; University of Go¨ttingen: Go¨ttingen: Germany, 1986.
(14) Sheldrick, G. M. SADABS User Guide; University of Go¨ttingen:
Go¨ttingen, Germany, 1986.
(15) Natarajan, S. J. Solid State Chem. 1999, 149, 50.
4498 Inorganic Chemistry, Vol. 41, No. 17, 2002

3-Dimensional Open-Framework Neodymium Oxalates
Figure 1. ORTEP diagram for (a) [NH3CH2CH(NH3)CH3][Nd(C2O4)2-
(HCOO)]‚H2O (I) and (b) [OC(CH3)NCH2CH(CH3)NH3][Nd(C2O4)2]‚H2O
(II).
hydrogen atoms other than one oxygen atom in I and a carbon
atom in II. Full-matrix least-squares structure refinement against
|F2| was carried out with the SHELXTL-PLUS16 package of
programs. Details of the final refinements are given in Table 2.
The selected bond distances and angles for compounds I are
presented in Tables 3 and 4 and for II in Tables 5 and 6.
Figure 2. The coordination environment around the Nd atom: (a) the
monocapped square antiprism in I and (b) the idealized D3h triply capped
trigonal prism in II.
Results and Discussion
The asymmetric units of I and II contains 24 and 23 non-
hydrogen atoms (Figure 1a,b). The frameworks of I and II
are built up of linkages between the Nd and the oxalate units,
with each Nd atom bound to nine oxygens, which in turn
are bound to carbon atoms, forming a network structure.
Conversely, the oxalate ions are connected to the neodymium
atoms forming the architecture. The Nd atoms have the rare
distorted square antiprism coordination capped on one square
face (Figure 2a) in I. In II, the Nd atoms have a common
idealized D3h triply capped trigonal prism coordination
(Figure 2b).17 The Nd-O distances are in the range 2.462-
(4)-2.531(4) Å (av 2.495 Å) for I and in the range 2.461-
(6)-2.529(7) Å (av 2.492 Å) for II. The O-Nd-O bond
angles for I are in the range 65.28(12)-143.80(14)° (av
98.78°) and 64.2(2)-145.4(2)° (av 98.76°) for II. The C-O
and O-C-O distances and angles are in the expected ranges.
The organic amine, 1,2-DAP, in I is diprotonated and
disordered and occupies the center of the 12-membered
channels. Such disorder of the amine molecules is observed
commonly in open-framework phosphates.15 The formic acid
in the reaction mixture occurs as formate ion in I and is
coordinated to the Nd atom. Acetic acid in the reaction
mixture reacts with 1,2-DAP, in the case of II, to form N-(2-
(16) Sheldrick, G. M. SHELXTL-PLUS, Program for Crystal Structure
Solution and Refinement; University of Go¨ttingen: Go¨ttingen, Ger-
many, 1993.
(17) AdVanced Inorganic Chemistry, 6th ed.; Cotton, F. A., Wilkinson, G.,
Murillo, C. A., Bochmann, M., Eds.; John Wiley: New York, 1998.
Inorganic Chemistry, Vol. 41, No. 17, 2002 4499

Vaidhyanathan et al.
Figure 4. Structure of I along the c axis showing the 12-membered
channel. The disordered amine molecules occupy the center of the channel
(not shown).
Figure 3. (a) Structure of I along the a axis showing the 12-membered
channels. Note the formate groups protrude into the channel. The amine
molecules are not shown for clarity. (b) Structure of II along the a axis
showing the 12-membered channels. Note that the N-(2-aminopropyl
acetimide) group protrudes into the channel.
Figure 5. Structure of II along the c axis showing the 12-membered
channel.
from the N-(2-aminopropyl acetimide) group in the case of
II (Figure 3a,b). The connectivity involving the in-plane and
the out-of-plane linkages of the oxalate units, in I and II,
along the b and c axis gives rise to 12-membered channels,
respectively (Figures 4 and 5). Clearly, both I and II are
truly three-dimensional structures with channels along all the
crystallographic directions.
The structures of I and II possess comparable features to
those of other framework oxalate structures described
recently in the literature.9,10 Nine coordination for the rare-
earth atoms has been encountered in some rare-earth car-
boxylates earlier, with the ninth coordination being provided
by a water molecule.11,12b The structures of I and II are to
be contrasted with the Sn(II) and Zn oxalate structures
reported recently.9,10b In the Sn(II) and Zn oxalates, the Sn
and Zn atoms are usually 6-coordinated, resulting in layered
architectures for the structures. Although the structure of II
is comparable to that of an yttrium oxalate reported by us,10a
the organic species in the latter, 2-methyl-3,4,5,6-tetrahy-
aminopropyl acetamide), which occurs in the more stable
tautomeric form as N-(2-aminopropyl acetimide). A reaction
between the acetic acid and the amine occurs through a
nucleophilic attack as shown below. The imido compound
is linked to Nd through the oxygen atom. The dangling
formate in I and N-(2-aminopropyl acetimide) in II both have
a high positional freedom.
The framework structures of I and II can be understood
in terms of the simpler building units formed by the linkages
between the Nd atoms and the oxalate units. The connectivity
between Nd and three oxalate units gives rise to a honeycomb-
like layer, with a 12-membered aperture in the bc plane. The
layers are connected through the fourth oxalate, acting like
a pillar, creating the three-dimensional structure with one-
dimensional channels as shown in Figure 3a. The ninth
coordination of Nd comes from the linkage of one of the
oxygen atoms of the formate group in the case of I, and
4500 Inorganic Chemistry, Vol. 41, No. 17, 2002

3-Dimensional Open-Framework Neodymium Oxalates
dropyrimid-1-ene, is free and occupies the channels, unlike
in II, where N-(2-aminopropyl acetimide) is directly linked
to neodymium. Furthermore, the yttrium atom is eight-
coordinated, unlike the bigger Nd, which is nine-coordinated
in both I and II. The higher coordination of the rare-earth
atoms in I, II, and the yttrium oxalate facilitates the formation
of three-dimensional structure by having three oxalates
coordinated by in-plane connectivity and one via out-of-plane
connection. Such connectivity is reminiscent of the phosphate-
oxalate structures, wherein sheets of the inorganic phosphates
are cross-linked by the out-of-plane oxalate units.18
Conclusions
Two new open-framework neodymium oxalates, with
dangling organic functional groups uniformly distributed in
the channels, are described. These oxalates serve as interest-
ing examples for the effective use of the ninth coordination
of the rare-earth ion. The structures differ from those of the
yttrium oxalates reported earlier, in that the functional groups
are present in the channels of the oxalates described in the
present study. The functional groups in I and II are amenable
for chemical manipulation.
Supporting Information Available: Two X-ray crystallo-
graphic files, in CIF format. This material is available free of charge
via the Internet at http://pubs.acs.org.
(18) (a) Choudhury, A.; Natarajan, S.; Rao, C. N. R. Chem. Mater. 1999,
11, 3216. (b) Choudhury, A.; Natarajan, S.; Rao, C. N. R. Chem. Eur.
J. 2000, 6, 1168.
IC020197R
Inorganic Chemistry, Vol. 41, No. 17, 2002 4501