Synthesis and characterization of new iron phosphatooxalates: [(S)-C5H14N2] [Fe4(C2O4)3(HPO4) 2(H2O)2] and [(S)-C5H14N2] [Fe4(C2O4)3(HPO4) 2]

Article abstract of DOI:10.1006/jssc.2000.9081

Two new organically templated iron(II) phosphatooxalates, [(S)-C₅H₁₄N₂] [Fe₄(C₂O₄)₃(HPO₄) ₂(H₂O)₂] (1) and [(S)-C₅H₁₄N₂] [Fe₄(C₂O₄)₃(HPO₄) ₂] (2), have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction and Moessbauer spectroscopy. Crystal data are as follows: compound 1, triclinic, P1 (No. 1), a = 7.6999(4) A, b = 7.9542(4) A, c = 9.8262(5) A, α = 74.8444(7)°, β = 81.7716(8)°, γ = 85.4075(8)°, V = 574.34(8) A³, Z = 1, and R1 = 0.0255; compound 2, monoclinic, P2₁ (No. 4), a = 7.5943(8) A, b = 7.8172(8) A, c = 18.318(2) A, β = 99.111(2)°, V = 1073.8(3) A³, Z = 2, and R1 = 0.0281. The structure of 1 consists of dimers of edge-sharing FeO₆ octahedra that are linked by phosphate and oxalate groups to generate a three-dimensional framework with intersecting tunnels parallel to the [100] and [010] directions. Diprotonated (S)-2-methylpiperazinium cations are located at the intersections of these tunnels. Compound 1 crystallizes as a minor product when a racemic mixture of 2-methylpiperazine is used in the synthesis, and can be prepared as a major product with a small amount of 2 if optically pure (S)-2-methylpiperzine is used. The structure of 2 is similar to that of 1 except that the coordination around the iron centers in the dimer are square pyramidal and octahedral. The two compounds are the first 3-dimensional phosphatooxalates containing a chiral amine.

Full text of DOI:10.1006/jssc.2000.9081

Journal of Solid State Chemistry 157, 233}239 (2001)
doi:10.1006/jssc.2000.9081, available online at http://www.idealibrary.com on
Synthesis and Characterization of New Iron Phosphatooxalates:
[
(S)-C H N ] [Fe (C O ) (HPO ) (H O) ] and [(S)-C H N ]
5
14
2
4
2
4 3
4 2
2
2
5
14
2
[
Fe (C O ) (HPO ) ]
4
2
4 3
4 2
Wen-Jung Chang,* Hsiu-Mei Lin,- and Kwang-Hwa Lii*ꢁ-ꢁꢀ
*
Department of Chemistry, National Central University, Chungli, Taiwan, Republic of China; and -Institute of Chemistry, Academia Sinica,
Taipei, Taiwan, Republic of China
Received September 26, 2000; in revised form December 4, 2000; accepted December 8, 2000
variety of means of connection. An interesting variant of the
metal phosphates is obtained by incorporating the oxalate
unit in the materials. A large number of phosphatooxalates
) ] (2), have been synthesized under hy- of Fe (8}13), V (14), Al (15, 16), Ga (17}19), In (20), and Mn
Two new organically templated iron(II) phosphatooxalates,
[
N
(S)-C
] [Fe
drothermal conditions and characterized by single-crystal X-ray (21) have been reported during past few years. In this new
5
H
14
N
2
] [Fe
4
2
(C O
4
)
3
(HPO
4
)
2
(H O)
2 2
] (1) and [(S)-C
5
H
14
2
4
(C
O
2 4
)
3
(HPO
4
2
di4raction and Mo
follows: compound 1, triclinic, P1 (No. 1), a ؍ 7.6999(4) A
.9542(4) A, c ؍ 9.8262(5) A, a ؍ 74.8444(7)3, b ؍ 81.7716(8)3,
c؍ 85.4075(8)3, V ؍ 574.34(8) A
compound 2, monoclinic, P2 (No. 4), a ؍ 7.5943(8) A
.8172(8) A, c ؍ 18.318(2) A, b ؍ 99.111(2)3, V ؍ 1073.8(3) A
Z ؍ 2, and R1 ؍ 0.0281. The structure of 1 consists of dimers of
edge-sharing FeO octahedra that are linked by phosphate and
oxalate groups to generate a three-dimensional framework with
K
ssbauer spectroscopy. Crystal data are as
class of organically modi"ed inorganic materials, there have
been relatively more reports on the Fe}PO}Ox system. All
of these iron compounds adopt three-dimensional frame-
work structures. Most of them consist of anionic frame-
works templated with organic amines in protonated forms,
while a few contain neutral frameworks without amine
templates. In our continuing research on this system, we
have discovered two novel iron phosphatooxalates tem-
>
, b ؍
7
>
>
3
>
, Z ؍ 1, and R1 ؍ 0.0255;
, b ؍
1
>
3
7
>
>
> ,
6
intersecting tunnels parallel to the [100] and [010] directions. plated with a chiral amine, [(S)-C H N ][Fe (C O )
ꢂ ꢀꢃ ꢄ ꢄ ꢃ ꢅ
Diprotonated (S)-2-methylpiperazinium cations are located at (HPO ) (H O) ] (1) and [(S)-C H N ][Fe (C O )
ꢃ ꢄ ꢂ ꢀꢃ ꢄ ꢄ ꢃ ꢅ
the intersections of these tunnels. Compound 1 crystallizes as (HPO ) ] (2). Most interestingly, only the chiral species acts
ꢃ
ꢄ
ꢄ
ꢃ
ꢃ ꢄ
a minor product when a racemic mixture of 2-methylpiperazine
is used in the synthesis, and can be prepared as a major product
with a small amount of 2 if optically pure (S)-2-methylpiperzine
is used. The structure of 2 is similar to that of 1 except that the
coordination around the iron centers in the dimer are square
pyramidal and octahedral. The two compounds are the 5rst
as a template in 1, although a racemic mix of 2-methyl-
piperazine is used in the synthesis. Compound 2 crystallizes
as a minor product when the chiral amine (S)-2-methyl-
piperazine is used as a template. To our knowledge, no
three-dimensional metal phosphate-oxalate framework
templated with a chiral amine has been reported before this
work.
3
-dimensional phosphatooxalates containing a chiral amine.
(
2001 Academic Press
EXPERIMENTAL SECTION
INTRODUCTION
Synthesis. The compounds were synthesized hydrother-
Recently, many research activities have focused on the mally in a 23-mL Te#on-lined autoclave under autogenous
synthesis of new open-framework metal phosphates, owing pressure. Reaction of a racemic mixture of 2-methyl-
to their diverse structural chemistry and potential applica- piperazine (5 mmol), iron metal powder (3 mmol), H PO
ꢅ
ꢃ
tions (1). In the context of building open frameworks, it is (7 mmol), oxalic acid (4 mmol), and H O (10 mL) at 1653C
ꢄ
also possible to use organic molecules in the skeleton (2}7). for 3 days followed by slow cooling at 103C/h to room
As compared with inorganic phosphates, the organic mol- temperature produced a small amount of red crystals of
ecules have larger sizes of polyhedral centers and a wide [(S)-C H N ][Fe (C O ) (HPO ) (H O) ] (1) and or-
ꢂ ꢀꢃ ꢄ
ꢃ
ꢄ ꢃ ꢅ
ꢂ ꢀꢃ ꢄ
ꢃ ꢄ ꢄ
ꢄ ꢃ ꢅ
ꢄ
ange crystals of [C H N ][Fe (C O ) (HPO ) ] (3) as the
ꢃ
ꢃ ꢄ
major products. The "lling rate of the bomb was about
50%. The initial and "nal pH values were 4.6 and 5.9,
ꢀ
To whom correspondence should be addressed. E-mail: liikh@cc.ncu.
edu.tw.
2
33
0
022-4596/01 $35.00
Copyright ( 2001 by Academic Press
All rights of reproduction in any form reserved.

2
34
CHANG, LIN, AND LII
respectively. The crystal that was selected for single-crystal
X-ray di!raction contained (S)-2-methylpiperazinium ca-
tions. In theory [(R)-C H N ][Fe (C O ) (HPO )
TABLE 1
Crystal Data and Structure Re5nement Parameters for [(S)-
C
5
H
14
N
2
][Fe
4
(C
2
O
4
)
3
(HPO
4
2
) (H
2
O)
2
] (1) and [(S)-C
5
H
14
N
2
]
ꢂ ꢀꢃ ꢄ
ꢃ
ꢄ ꢃ ꢅ
ꢃ ꢄ
[
Fe
4
(C
2
O
)
4 3
(HPO
4
)
2
] (2)
(
H O) ] should also crystallize as a minor product. A sub-
ꢄ
ꢄ
sequent reaction using (S)-(#)-2-methylpiperazine instead
of racemic 2-methylpiperazine produced compound 1 in
a yield of about 70% and a small amount of orange crystals
1
2
Empirical formula
C
Fe H N O
P
C
Fe H N O
ꢀꢀ ꢀꢇ
781.6
P
ꢀꢀ
ꢃ
ꢄꢆ ꢄ ꢄꢄ ꢄ
ꢃ
ꢄ
ꢄꢆ ꢄ
of [(S)-C H N ][Fe (C O ) (HPO ) ] (2) (22). Energy Formula weight
ꢂ ꢀꢃ ꢄ ꢄ ꢃ ꢅ ꢃ ꢄ
dispersive X-ray analysis con"rmed the presence of iron and Crystal color
817.63
red
ꢃ
orange
0.6;0.15;0.1
monoclinic
Crystal size, mmꢅ
Crystal system
Space group
0.25;0.15;0.1
triclinic
P1 (No. 1)
phosphorus in all three compounds. Suitable crystals were
selected for single-crystal X-ray structure determination.
The red crystals were manually separated from the orange
crystals to give pure 1 as judged by visual microscopic
examination and by comparison of the X-ray powder pat-
tern to the pattern simulated from the atomic coordinates
derived from single-crystal study. Elemental analysis of
P2 (No. 4)
ꢀ
Unit cell dimensions
a"7.6999(4)
b"7.9542(4)
c"9.8262(5)
a"74.8444(7)
b"81.7716(8)
c"85.4075(8)
7.5943(8)
7.8172(8)
18.318(2)
90
99.111(2)
90
1073.8(3)
2
2.413
1
con"rmed the stoichiometry. Analysis found the following:
C, 16.1; H, 2.41; N, 3.38. Calculations were as follows: C,
6.2; H, 2.46; N, 3.42%.
<
1
"574.34(8)
Z
1
D
¹
!ꢀ#$, g)cm\ꢅ
, 3C
2.364
#
23
23
0.71073
2.91
TGA and M o( ssbauer spectroscopy. Thermogravimetric j (MoKa), A
analysis for 1 was carried out on a Perkin}Elmer TGA7 l, mm\ꢀ
>
0.71073
2.73
2
h
, 3
ꢁ!ꢂ
Index ranges
56
56.6
thermal analyzer under oxygen atmosphere in the range
0}9003C at a heating rate of 103C/min. The X-ray powder
pattern of the "nal decomposition product revealed the
presence of Fe (P O ) (23). The ꢂꢉFe Mo
ssbauer measure- Data collected
!96h69,
!106h69,
!86k610
3
!
106k610
!
126l611
!226l623
K
5457
6826
ꢃ
ꢄ ꢉ ꢅ
ments were made on a constant-acceleration instrument at Unique data
4243 [F '4p(F )]
3321 [F '4p(F )]
ꢃ
ꢃ
ꢃ ꢃ
Number of variables
Goodness-of-"t
371
352
room temperature. Isomer shifts are reported with respect
to an iron foil standard at 300 K.
1.075
1.020
R indices [F '4p(F )] R1"0.0255,
R1"0.0281,
wR2"0.0703
R1"0.0357,
wR2"0.0744
0.05(2)
ꢃ
ꢃ
wR2"0.0725
R1"0.0257,
wR2"0.0727
0.0(2)
Single-crystal X-ray diwraction. A suitable single crystal
of each compound was selected for indexing and intensity
data collection on a Siemens Smart-CCD di!ractometer
R indices (all data)
Flack x parameter
equipped with a normal focus, 3-kW sealed tube X-ray (*o)ꢁ!ꢂꢁꢁ*ꢄ, e)A
>
\ꢅ
0.49, !0.39
0.62, !0.35
source at room temperature. Empirical absorption correc-
tions were applied. The structures were solved by direct
methods and di!erence Fourier syntheses. Bond-valence
calculations indicate that all the Fe atoms are divalent and
Note. R1"+""F "!"F ""/+"F ". wR2"++[w(Fꢄ!Fꢄ)ꢄ]/+[w(Fꢄ)ꢄ],ꢀꢈꢄ,
ꢃ
#
ꢃ
ꢃ
ꢃ
ꢃ
w"1/[pꢄ(F )ꢄ#(aP)ꢄ#bP], P"[Max(F , 0)#2(F )ꢄ]/3, where a"
ꢃ
ꢃ
#
0
.0494 and b"0.36 for 1, and a"0.0460 and b"0 for 2.
all phosphate ligands are HPOꢄ\ (24). Compound 1 adopts
ꢃ
a new structure, while the structure of 2 is closely related to coordinates are in Table 2, and selected bond distances are
that of [C H N ][Fe (C O ) (HPO ) ], where [C H
in Table 3. Crystal data for 3 are as follows: monoclinic,
ꢃ ꢀꢄ ꢄ
ꢃ
ꢄ ꢃ ꢅ
ꢃ ꢄ
ꢃ ꢀꢄ
N ]ꢄ> is a piperazinium cation (8). Compound 3 is isotypic P2 /c, a"7.5949(7) A
> > >
, b"7.8208(7) A, c"18.326(2) A,
ꢄ
ꢀ
to [C H N ][Fe (C O ) (HPO ) ]. All of the hydrogen b"99.155(2)3, <"1074.6(3) A
>
ꢅ, Z"2, D "2.415 g
ꢃ ꢀꢄ ꢄ
ꢃ
ꢄ ꢃ ꢅ
ꢃ ꢄ
#!ꢀ#
>
, 1878 absorption corrected re#ections
atoms were positioned geometrically and re"ned using cm\ꢅ, j"0.71073 A
a riding model with "xed isotropic thermal parameters. The with F '4p(F ) measured at 233C on an orange crystal
ꢃ
ꢃ
"
nal cycles of least-squares re"nement included atomic (2h "56.43), R1"0.0365, and wR2"0.0982.
ꢁ!ꢂ
coordinates and anisotropic thermal parameters for all non-
hydrogen atoms. The reliability factors converged to
R1"0.0255, wR2"0.0727, and S"1.075 for 1 and R1"
RESULTS AND DISCUSSION
0
.0281, wR2"0.0744, and S"1.020 for 2. The Flack
TGA and M o( ssbauer spectroscopy. TGA data for 1 in
x parameters were 0.0(2) and 0.05(2) for 1 and 2, respectively, oxygen show a broad weight loss that begins at about
indicative of correct absolute structures. All calculations 2003C, has a maximum rate at 3503C, and is complete above
were performed using the SHELXTL Version 5.1 software 7003C. The weight loss is attributed to dehydration of hy-
package (25). The crystal data and structure re"nement drogen phosphate groups, deprotonation of 2-methyl-
parameters for 1 and 2 are given in Table 1, the atomic piperazinium cations, decomposition of oxalate anions, and

SYNTHESIS AND CHARACTERIZATION OF NEW IRON PHOSPHATOOXALATES
235
TABLE 2
Atomic Coordinates and Temperature Factors (A
TABLE 2=Continued
2
>
) for [(S)-
C
5
H
14
N
2
][Fe
4
(C
O
2 4
)
3
(HPO
4
)
2
(H
2 2
O) ] (1) and [(S)-C
5 14
H N
2
]
Atom
x
y
z
;?
%
ꢅ
[Fe
4
(C
2
4
O )
3
(HPO
4 2
)
] (2)
1
Compound 22
Atom
x
y
z
;?
Fe(1)
Fe(2)
Fe(3)
Fe(4)
P(1)
P(2)
O(1)
O(2)
O(3)
O(4)
O(5)
O(6)
O(7)
O(8)
O(9)
O(10)
O(11)
O(12)
O(13)
O(14)
O(15)
O(16)
O(17)
O(18)
O(19)
H(1P)
O(20)
H(2P)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
H(7A)
C(8)
H(8A)
H(8B)
C(9)
H(9A)
H(9B)
C(10)
H(10A)
H(10B)
C(11)
H(11A)
H(11B)
H(11C)
N(1)
0.36475(9)
0.7123(1)
0.62826(9)
0.2792(1)
0.4497(1)
0.5586(1)
0.4313(5)
0.1883(4)
0.5769(4)
0.4965(4)
0.3014(4)
0.1386(4)
0.5762(4)
0.9421(5)
0.8790(4)
0.5819(5)
0.8039(4)
0.4095(4)
0.4848(4)
0.6898(4)
0.8558(4)
0.4148(5)
0.0522(4)
0.1102(4)
0.2629(5)
0.2736(5)
0.7514(5)
0.7496(5)
0.9405(6)
0.9718(6)
0.0232(6)
0.0527(7)
0.4134(6)
0.5778(5)
0.8515(6)
0.8288(6)
0.0569(7)
0.0355(7)
0.0819(7)
0.2162(7)
0.2444(7)
0.3194(7)
0.0105(7)
0.9865(7)
0.0281(7)
0.6881(7)
0.5895(7)
0.6610(7)
0.7091(7)
0.8964(5)
0.9159(5)
0.8026(5)
0.1774(5)
0.1664(5)
0.2694(5)
0.21560(9)
0.95835(9)
0.08735(9)
0.34940(9)
0.7285(2)
0.5752(2)
0.4615(5)
0.0073(6)
0.0964(6)
0.5899(6)
0.2595(6)
0.2909(6)
0.7463(6)
0.8960(6)
0.1778(6)
0.8350(5)
0.2874(6)
0.2010(6)
0.2071(6)
0.0420(6)
0.0157(6)
0.5572(6)
0.4052(5)
0.1378(6)
0.8231(6)
0.9174(6)
0.4952(6)
0.4004(6)
0.2905(8)
0.1318(8)
0.1769(7)
0.0147(8)
0.1980(8)
0.1019(8)
0.6462(6)
0.7552(6)
0.7920(7)
0.9025(7)
0.8100(7)
0.7041(7)
0.5995(7)
0.7787(7)
0.5609(7)
0.5437(7)
0.4494(7)
0.5366(7)
0.5942(7)
0.5158(7)
0.4297(7)
0.6809(5)
0.5808(5)
0.7318(5)
0.6635(6)
0.7616(6)
0.6045(6)
0.38359(4)
0.43997(5)
0.11549(4)
0.05819(5)
0.05537(7)
0.44558(7)
0.3938(2)
0.3649(2)
0.3403(2)
0.5207(2)
0.2614(2)
0.4456(2)
0.4109(2)
0.3957(2)
0.4674(2)
0.1075(2)
0.1339(2)
0.1572(2)
0.0187(2)
0.2367(2)
0.0497(2)
0.0892(2)
0.1088(2)
0.0266(2)
0.0431(2)
0.0248(2)
0.4561(2)
0.4751(2)
0.1031(3)
0.0554(3)
0.4416(3)
0.3960(3)
0.2274(3)
0.2721(3)
0.2606(2)
0.2838(2)
0.1871(3)
0.2081(3)
0.1373(3)
0.2343(3)
0.2102(3)
0.2386(3)
0.3060(3)
0.3559(3)
0.2850(3)
0.2552(3)
0.2260(3)
0.3039(3)
0.2323(3)
0.1850(2)
0.1633(2)
0.1572(2)
0.3088(2)
0.3335(2)
0.3339(2)
0.0150(2)
0.0168(2)
0.0157(2)
0.0163(2)
0.0132(3)
0.0131(3)
0.0175(8)
0.0223(9)
0.0189(9)
0.0202(9)
0.024(1)
0.0212(9)
0.0199(9)
0.0216(9)
0.0221(9)
0.0193(9)
0.0242(9)
0.0197(9)
0.0197(9)
0.023(1)
0.0212(9)
0.0210(9)
0.0191(9)
0.0219(9)
0.026(1)
0.0384
%
ꢅ
1
Compound 12
0.59482(6)
0.31879(5)
Fe(1)
Fe(2)
Fe(3)
Fe(4)
P(1)
P(2)
O(1)
O(2)
O(3)
O(4)
O(5)
O(6)
O(7)
O(8)
O(9)
O(10)
O(11)
O(12)
O(13)
O(14)
O(15)
O(16)
O(17)
O(18)
O(19)
H(1P)
O(20)
H(2P)
O(21)
O(22)
C(1)
0.91140(6)
0.59107(6)
0.63062(6) !0.35143(5)
0.95213(6) !0.07778(5)
0.73064(5)
0.83930(5)
0.21660(5)
0.10437(5)
0.8800(1)
0.0718(1)
0.6412(3)
0.9226(3)
0.7608(4)
0.7682(3)
0.7051(4)
0.4968(3)
0.8323(4)
0.7527(4)
0.8173(4)
0.0459(3)
0.3049(4)
0.0266(3)
0.1634(4)
0.1813(3)
0.2435(3)
0.4500(3)
0.1241(4)
0.8883(3)
0.8967(3)
0.8205(3)
0.0633(4)
0.0351(4)
0.1103(4)
0.1753(4)
0.5127(4)
0.4313(4)
0.7787(5)
0.7410(4)
0.1537(5)
0.1933(5)
0.4758(4)
0.4242(4)
0.3786(5)
0.2936(5)
0.4271(5)
0.4610(5)
0.5143(5)
0.4285(5)
0.5556(4)
0.6377(4)
0.5046(4)
0.5137(6)
0.5747(6)
0.4284(6)
0.5619(6)
0.6035(4)
0.6634(4)
0.6498(4)
0.3383(3)
0.2831(3)
0.2866(3)
0.0140(1)
0.0139(1)
0.0131(1)
0.0137(1)
0.0138(2)
0.0120(2)
0.0164(6)
0.0180(7)
0.0227(7)
0.0226(7)
0.0238(8)
0.0229(7)
0.0185(7)
0.0206(7)
0.0222(7)
0.0309(7)
0.0205(7)
0.0174(7)
0.0224(7)
0.0220(7)
0.0192(7)
0.0217(7)
0.0199(7)
0.0328(8)
0.0189(6)
0.0283
0.6915(1)
0.8456(1)
0.7295(5)
0.7907(4)
0.1659(5)
0.7853(5)
0.0951(5)
0.9593(5)
0.7083(5)
0.3597(4)
0.4292(5)
0.4278(4)
0.8173(5)
0.7534(4)
0.3842(5)
0.7385(5)
0.4469(4)
0.5900(4)
0.8365(5)
0.0757(5)
0.4879(4)
0.4504(4)
0.0458(4)
0.0556(4)
0.1196(4)
0.1923(5)
0.7060(6)
0.8429(6)
0.2801(6)
0.2430(6)
0.2638(6)
0.3046(6)
0.2017(5)
0.2008(5)
0.3067(6)
0.2506(6)
0.3085(6)
0.5798(6)
0.5963(6)
0.6947(6)
0.4756(5)
0.5352(5)
0.4654(5)
0.0115(6)
0.9486(6)
0.9573(6)
0.0092(6)
0.2946(5)
0.2331(5)
0.3038(5)
0.4901(4)
0.4881(4)
0.5515(4)
!0.1056(1)
0.3428(1)
0.4743(4)
0.4163(4)
0.6804(4)
0.8081(4)
0.3847(4)
0.7177(4)
0.0903(4)
0.2711(4)
0.5650(4)
0.2688(4)
!0.2406(4)
!0.1822(4)
!0.4268(4)
!0.5737(4)
!0.1448(4)
!0.4801(4)
0.1470(4)
0.0253(4)
!0.1382(4)
!0.0960(4)
0.3869(4)
0.0218(9)
0.0328
0.0238(7)
0.0358
0.016(1)
0.016(1)
0.017(1)
0.019(1)
0.016(1)
0.017(1)
0.022(1)
0.0269
0.031(1)
0.0366
0.0366
0.030(1)
0.0365
0.0365
0.028(1)
0.0338
0.0338
0.036(1)
0.0546
0.0546
0.0546
0.0224(9)
0.0269
0.0269
0.030(1)
0.0360
0.4927(4)
!0.3127(4)
!0.0185(4)
0.5475(5)
0.0206(7)
0.0252(8)
0.0149(8)
0.0151(8)
0.0163(8)
0.0152(8)
0.0162(8)
0.0172(9)
0.0244(7)
0.0293
0.0284(9)
0.0341
0.0341
0.032(1)
0.0384
0.0384
0.0271(7)
0.0325
0.0325
0.038(1)
0.0573
0.0573
0.0573
0.0275(8)
0.0330
0.0330
0.0274(6)
0.0329
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
0.6869(5)
0.5607(5)
0.3912(5)
!0.3097(5)
!0.1421(6)
0.0782(5)
!0.0118(5)
0.2285(5)
H(7A)
C(8)
H(8A)
H(8B)
C(9)
H(9A)
H(9B)
C(10)
H(10A)
H(10B)
C(11)
H(11A)
H(11B)
H(11C)
N(1)
0.2767(5)
0.3200(5)
0.0795(6)
0.1626(6)
0.0345(6)
!0.0672(5)
!0.1218(5)
!0.1544(5)
0.1377(7)
0.0410(7)
0.1810(7)
0.2287(7)
0.0017(4)
H(12A)
H(12B)
H(2)
H(13A)
H(13B)
H(12A)
H(12B)
N(2)
H(13A)
H(13B)
!0.0855(4)
0.0838(4)
0.0360
0.1672(4)
0.0933(4)
0.2593(4)
?;
is de"ned as one-third of the trace of the orthogonalized ;GH
%
ꢅ
0.0329
tensor.

2
36
CHANG, LIN, AND LII
TABLE 3
Selected Bond Lengths (A
>
) for [(S)-C
5
H
4
14
N
2
][Fe
4
(C
2
O
4
4 3
)
2
(
(
HPO
2)
4
)
2
(H
2
2
O) ] (1) and [(S)-C
5 14
H N
2
][Fe
(C
2
O
)
4 3
(HPO ) ]
1
Compound 12
Fe(1)}O(1)
Fe(1)}O(3)
Fe(1)}O(5)
Fe(2)}O(1)
Fe(2)}O(7)
Fe(2)}O(9)
Fe(3)}O(11)
Fe(3)}O(13)
Fe(3)}O(15)
Fe(4)}O(11)
Fe(4)}O(17)
Fe(4)}O(21)
P(1)}O(4)
P(1)}O(12)
P(2)}O(2)
P(2)}O(17)
O(19)}H(1P)
C(1)}O(1)
C(1)}C(2)
C(2)}O(11)
C(3)}O(9)
2.159(3)
2.208(3)
2.144(3)
2.194(3)
1.977(3)
2.214(3)
2.134(3)
2.205(4)
2.126(3)
2.221(3)
1.967(3)
2.176(3)
1.512(3)
1.538(3)
1.536(3)
1.511(3)
0.82
1.277(5)
1.569(3)
1.261(5)
1.265(6)
1.248(6)
1.256(6)
1.549(5)
1.250(6)
1.527(6)
0.98
Fe(1)}O(2)
Fe(1)}O(4)
Fe(1)}O(6)
Fe(2)}O(2)
Fe(2)}O(8)
Fe(2)}O(10)
Fe(3)}O(12)
Fe(3)}O(14)
Fe(3)}O(16)
Fe(4)}O(12)
Fe(4)}O(18)
Fe(4)}O(22)
P(1)}O(7)
P(1)}O(19)
P(2)}O(14)
P(2)}O(20)
O(20)}H(2P)
C(1)}O(16)
C(2)}O(6)
C(3)}O(3)
C(3)}C(4)
C(4)}O(8)
C(5)}O(21)
C(6)}O(15)
C(7)}C(8)
C(7)}N(1)
C(8)}N(2)
2.179(3)
1.979(3)
2.239(6)
2.126(3)
2.180(3)
2.188(3)
2.139(3)
1.985(3)
2.241(3)
2.117(3)
2.173(3)
2.193(4)
1.516(3)
1.588(3)
1.520(3)
1.594(3)
0.82
1.219(5)
1.249(6)
1.238(6)
1.545(5)
1.253(6)
1.249(6)
1.261(6)
1.528(5)
1.499(5)
1.489(5)
0.97
FIG. 1. Thermogravimetric analysis of 1 in #owing oxygen at 103C
min\ꢀ.
the equation
3
(C H N )[Fe (C O ) (HPO ) (H O) ]#3 O
ꢂ ꢀꢃ ꢄ ꢄ ꢃ ꢅ ꢃ ꢄ ꢄ
ꢃ
ꢄ
ꢄ
PFe (P O ) #4 Fe O #3 C H N
ꢄ ꢉ ꢅ ꢄ ꢅ ꢂ ꢀꢄ ꢄ
ꢃ
#
12 H O#9 CO#9 CO .
C(4)}O(5)
C(5)}O(13)
C(5)}C(6)
ꢄ ꢄ
A sample of 1 was heated in air at 2203C for 4 h. A powder
X-ray di!raction of the product indicated that it was
amorphous and 1 was not transformed to 2.
The room temperature ꢂꢉFe Mo
K ssbauer spectrum of 1
was least-squares "tted by one doublet (Fig. 2). The ob-
C(6)}O(22)
C(7)}C(11)
C(7)}H(7A)
C(8)}H(8A)
C(9)}C(10)
C(9)}H(9A)
C(10)}N(1)
C(10)}H(10B)
C(11)}H(11B)
N(1)}H(12A)
N(2)}H(13A)
0.97
1.496(6)
0.97
1.513(5)
0.97
0.96
C(8)}H(8B)
C(9)}N(2)
1.463(6)
0.97
0.97
0.96
0.96
C(9)}H(9B)
C(10)}H(10A)
C(11)}H(11A)
C(11)}H(11C)
N(1)}H(12B)
N(2)}H(13B)
tained parameters are d (isomer shift)"1.20 mm s\ꢀ, *E
/
(
quadrupole splitting)"2.65 mm s\ꢀ, and ! (full-width at
half-height)"0.34 mm s\ꢀ. The large quadrupole splitting
corresponds to large octahedral distortion. The isomer shift
is characteristic of high-spin Fe''. According to Menil, the
usual ranges of isomer shifts in oxides are 0.29}0.50 and
1.03}1.28 mm s\ꢀ for Fe''' and Fe'' in six-ccordination, re-
spectively (26). Therefore, the valence of the iron atoms in
0.90
0.90
0.90
0.90
1
Compound 22
Fe(1)}O(1)
Fe(1)}O(3)
Fe(1)}O(5)
Fe(2)}O(3)
Fe(2)}O(7)
Fe(2)}O(9)
Fe(3)}O(11)
Fe(3)}O(13)
Fe(3)}O(15)
Fe(4)}O(13)
Fe(4)}O(17)
P(1)}O(10)
P(1)}O(16)
P(2)}O(1)
1.989(4)
2.120(3)
2.240(4)
2.227(4)
1.981(4)
2.144(4)
2.049(4)
2.143(4)
2.326(3)
2.134(4)
2.127(3)
1.520(4)
1.517(4)
1.527(4)
1.496(4)
Fe(1)}O(2)
Fe(1)}O(4)
Fe(1)}O(6)
Fe(2)}O(4)
Fe(2)}O(8)
Fe(3)}O(10)
Fe(3)}O(12)
Fe(3)}O(14)
Fe(4)}O(12)
Fe(4)}O(16)
Fe(4)}O(18)
P(1)}O(13)
P(1)}O(19)
P(2)}O(4)
2.102(4)
2.137(4)
2.281(3)
2.111(3)
2.094(4)
2.005(4)
2.129(3)
2.224(4)
2.247(4)
1.959(4)
2.117(4)
1.527(3)
1.584(4)
1.528(3)
1.576(4)
1
is con"rmed by MoK ssbauer spectroscopy.
P(2)}O(7)
P(2)}O(20)
release of organic components, giving Fe (P O ) and
ꢃ
ꢄ ꢉ ꢅ
Fe O as the "nal products. The observed total weight loss
ꢄ ꢅ
of 46.8% is close to the calculated value 47.5% according to
FIG. 2. MoK ssbauer spectroscopy of 1 at 300 K.

SYNTHESIS AND CHARACTERIZATION OF NEW IRON PHOSPHATOOXALATES
237
dimers, thus forming a double chain parallel to the b axis
Fig. 4). Each double chain is linked to four others by
(
oxalate ligands to generate a three-dimensional framework
that delimits intersecting channels running along the [010]
and [100] directions. Within the channels parallel to [010]
are eight-membered rings containing four iron}oxygen oc-
tahedra and four oxalate units, whereas the other channels,
parallel to [100], are delimited by eight-ring apertures
containing four iron}oxygen octahedra, two phosphate tet-
rahedra, and two oxalate units. The (S)-2-methylpiperazin-
ium cations are located at the intersections of these channels
and are hydrogen-bonded to framework oxygen atoms. One
of the nitrogen atoms of the cation, N(1), is hydrogen-
bonded to O(3) at 2.79 A
close oxygen neighbors.
>
, but the other nitrogen has no
The local coordinations of the framework atoms in 2 are
shown in Fig. 5. It comprises FeO , FeO , HPO , and
ꢇ
ꢂ
ꢃ
C O moieties. The iron atoms show two di!erent coord-
ꢄ ꢃ
FIG. 3. A fragment of the structure of 1 (50% thermal ellipsoids) ination spheres. The FeO environment of Fe(1) and Fe(3) is
ꢇ
showing the basic structural building units. O(10) and O(18) are water
oxygen atoms.
similar to that of Fe(1) and Fe(3) in 1; namely, the iron atom
is coordinated by two bidentate oxalate and two phosphate
units. In contrast Fe(2) and Fe(4) in 2 are in "ve-fold coord-
Description of the structures. The local coordinations of ination with a square pyramidal geometry. Of the "ve oxy-
the framework atoms in 1 are shown in Fig. 3. It comprises gen atoms, two belong to two phosphate groups and two to
FeO , HPO , and C O moieties. All the four distinct Fe'' a bidentate oxalate unit, while the remaining oxygen, which
ꢇ
ꢃ
ꢄ ꢃ
atoms are in six-coordination with a distorted octahedral is at the apex of the pyramid, is from a monodentate oxalate
geometry, but they do not display the same environment. unit. The four basal ligand atoms and the iron atom are
Both Fe(1) and Fe(3) are coordinated by two bidentate nearly coplanar. The axial bond is longer than the equato-
oxalate and two phosphate units, while both Fe(2) and Fe(4) rial bonds, as is commonly found. The structural feature of
by one bidentate oxalate, one monodentate oxalate, two 2 is also an edge-sharing dimer formed of two iron}oxygen
phosphate units, and one terminal water molecule. The polyhedra. Each FeO octahedron shares an edge with
ꢇ
coordination by bidentate oxalate leads to highly distorted a FeO square pyramid to form a dimer that is linked by
ꢂ
octahedra for all four iron atoms, as indicated by the wide phosphate and oxalate ligands to adjacent dimers to form
range of Fe}O bond lengths and small O}Fe}O bond angles
subtended by the oxalate ligand, which also accounts for the
large quardrupole splitting in the MoK ssbauer spectrum.
There are three independent oxalate ligands in the structure:
C(1)C(2)O is a bridging bidentate ligand to both Fe(1) and
ꢃ
Fe(3) as well as a monodentate ligand to Fe(2) or Fe(4),
whereas the other two oxalates act only as bidentate ligands
that bridge Fe(1) and Fe(2) or Fe(3) and Fe(4). The two
distinct phosphorus atoms are all tetrahedrally coordina-
ted and linked through three oxygens to four adjacent
iron atoms, with the fourth coordination site in either case
corresponding to a terminal P}OH group. One of the three
oxygen atoms connects two iron atoms. The O}H groups
are involved in hydrogen bonding as inferred from the short
O2O distances (O(20)2O(21)"2.67 A
>
and O(19)2O(9)
"
2.76 A).
>
The structural feature of 1 is the presence of an edge-
sharing dimer formed of two Fe''-centered FeO octahedra.
ꢇ
The oxygen atoms involved in the shared edge serve as
FIG. 4. A polyhedral view of the structure of 1 along the [010] direc-
tion. Solid circles, carbon atoms; stippled circles, nitrogen atoms; large
corners for HPO and C O ligands. The dimer alternates
ꢃ
ꢄ ꢃ
with the HPO group, and each HPO connects three open circles, water oxygen atoms; small open circles, hydrogen atoms.
ꢃ
ꢃ

2
38
CHANG, LIN, AND LII
presence of (R)- and (S)-2-methylpiperazinium cations in the
structural channels. The connection of the building units in
3
is essentially the same as that in 2.
The title compounds are new members of a family of
hybrid framework structures. They are the "rst 3-dimen-
sional phosphatooxalates containing a chiral amine. The
structure of 1 contains coordinated water molecules and
six-coordinate iron atoms, whereas 2 comprises "ve- and
six-coordinate iron atoms. Although the framework com-
positions are di!erent, their structures are closely related
and the connection schemes of the building units are similar.
Both compounds contain diprotonated (S)-2-methyl-
piperazinium cations in the structural tunnels. Compound
2
2
can also be formed with piperazine or a racemic mix of
-methylpiperazine present as part of the structure. In con-
FIG. 5. A fragment of the structure of 2 (50% thermal ellipsoids)
showing the basic structural building units.
trast only the chiral species act as templates in compound 1.
This implies that the chirality of the organic amine is trans-
ferred to the host structure. The material may be potentially
a double chain in the same connection scheme as that in 1. useful if the framework does not collapse and if the chirality
Each double chain rides on a 2 -screw axis and is connected remains when the templates are removed. However, at-
ꢀ
to four others, generating intersecting channels running tempts to remove or exchange the templates have not been
parallel to [010] and [100] (Fig. 6). Within channels there successful probably because the framework contains ter-
are also eight-ring windows formed by the edges of iron} minal P}OH groups and coordinated water molecules, and
oxygen polyhedra, phosphate tetrahedral, and oxalate units. the organic cations form strong interactions with the frame-
Diprotonated (S)-2-methylpiperazinium cations are locked work, and as a result, they are necessary to maintaining the
in their positions at the intersections of the channels by integrity of the crystal structure. Therefore, the practical
hydrogen bonds to phosphate oxygens (N(1)2O(10)" value of this material is very limited. The synthesis of
2
.84 A
>
and N(2)2O(1)"2.77 A
>
). Compound 3, [C H
a chiral microporous material using chiral amine as a struc-
ꢂ ꢀꢃ
N ][Fe (C O ) (HPO ) ], crystallizes in the centrosym- ture-directing agent is a signi"cant challenge. Further work
ꢄ
ꢃ
ꢄ ꢃ ꢅ ꢃ ꢄ
metric space group P2 /c and is isotypic to [C H N ] on this theme is in progress.
ꢃ ꢀꢄ ꢄ
Fe (C O ) (HPO ) ], where the organic molecule is a dip-
ꢄ ꢃ ꢅ ꢃ ꢄ
rotonated piperazinium cation. The organic molecules in
ꢀ
[
ꢃ
ACKNOWLEDGMENTS
3
are found to be disordered because of the simultaneous
We thank the National Science Council for support, Ms. F.-L. Liao, and
Professor S.-L. Wang at National Tsing Hua University for X-ray intensity
data collection, and Professor T.-Y. Dong at National Sun Yat-Sen
University for Mo
K
ssbauer Spectroscopy measurements.
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2
3
4
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SYNTHESIS AND CHARACTERIZATION OF NEW IRON PHOSPHATOOXALATES
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1
1
(
1
1
1
ꢂ
ꢀꢃ
ꢄ
ꢃ
ꢄ
ꢃ ꢅ
ꢃ ꢄ
ꢄ
ꢄ
(
2000).
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sized using (R)-(-)-2-methylpiperazine as a template and structurally
characterized by single-crystal X-ray di!raction.
4
23. Fe (P O ) , "le number 36-318; Joint Committee on Powder Di!rac-
ꢃ
ꢄ ꢉ ꢅ
tion Standards, International Center of Di!raction Data, Swarthmore,
PA.
>
(
24. I. D. Brown and D. Altermatt, Acta Crystallogr. Sect. B 41, 244
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25. G. M. Sheldrick, SHELXTL Programs, Version 5.1, Bruker AXS
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1
1
1
1
26. F. Menil, J. Phys. Chem. Solids 46, 763 (1985).