Two organically templated niobium and zinconiobium fluorophosphates: Low temperature hydrothermal syntheses of NbOF(PO4)2(C 2H10N2)2 and Zn3(NbOF) (PO4)4(C2H10N2) 2

Article abstract of DOI:10.1021/ic061752i

Two new niobium and zinconiobium fluorophosphates, NbOF(PO ₄)₂(C₂H₁₀N₂)₂ (1) and Zn₃(NbOF)(PO₄)₄-(C₂H ₁₀N₂)₂ (2), have been prepared under hydrothermal conditions using ethylenediamine as a template. The structures were determined by single crystal diffraction to be triclinic, space group P1 (No. 2), a = 8.1075 (6) A, b = 9.8961 (7) A, c = 10.1420(8) A, α = 111.655(1)°, β = 111.51(1)°, γ = 93.206(1)°, V = 686.19(9) A³, and Z = 2 for 1 and orthorhombic, space group Fddd (No. 70), a = 9.1928(2) A, b = 14.2090(10) A, c = 32.2971 (6) A, V = 4218.66(12) A³, and Z = 8 for 2, respectively. Compound 1 is an infinite linear chain consisting of corner-sharing [Nb ₂P₂] 4-MRs bridged at the Nb centers with organic amines situated between chains, and compound 2, containing the chains similar to that in 1, forms a zeotype framework with organic amines situated in the gismondine-type [4⁶8⁴] cavities. The topology of 2 was previously unknown with vertex symbol 4·4·4·4· 8·8 (vertex 1), 4·4·4·8₂·8· 8 (vertex 2), 4·4·8·8·8₂·8 ₂ (vertex 3), and 4·4·4·8 ₂·8·8 (vertex 4). The topological relationships between the 4-connected network of 2 and several reported (3,4)-connected networks were discussed.

Full text of DOI:10.1021/ic061752i

Inorg. Chem. 2007, 46, 231−237
Two Organically Templated Niobium and Zinconiobium
Fluorophosphates: Low Temperature Hydrothermal Syntheses of
NbOF(PO4)2(C2H10N2)2 and Zn3(NbOF)(PO4)4(C2H10N2)2
Guang-Zhen Liu, Shou-Tian Zheng, and Guo-Yu Yang*
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of
Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, China
Received September 15, 2006
Two new niobium and zinconiobium fluorophosphates, NbOF(PO4)2(C2H10N2)2 (1) and Zn3(NbOF)(PO4)4-(C2H10N2)2
(2), have been prepared under hydrothermal conditions using ethylenediamine as a template. The structures were
determined by single crystal diffraction to be triclinic, space group P1
Å, c 10.1420(8) Å, R ) 111.655(1) â ) 111.51(1) γ ) 93.206(1)
orthorhombic, space group Fddd (No. 70), a 9.1928(2) Å, b 14.2090(10) Å, c
Å3, and Z
8 for 2, respectively. Compound 1 is an infinite linear chain consisting of corner-sharing [Nb2P2]
h
(No. 2), a
, V
686.19(9) Å3, and Z
32.2971 (6) Å, V
)
8.1075 (6) Å, b
)
)
9.8961 (7)
2 for 1 and
)
°
,
°
,
°
)
)
)
)
) 4218.66(12)
)
4-MRs bridged at the Nb centers with organic amines situated between chains, and compound 2, containing the
chains similar to that in 1, forms a zeotype framework with organic amines situated in the gismondine-type [4684]
cavities. The topology of 2 was previously unknown with vertex symbol 4
2), 4 82 82 (vertex 3), and 4 82 8 (vertex 4). The topological relationships between the 4-connected
network of 2 and several reported (3,4)-connected networks were discussed.
‚4‚4‚4‚8‚8 (vertex 1), 4‚4‚4‚82‚8‚8 (vertex
‚
4‚
8‚
8‚
‚
‚4‚4‚ ‚8‚
Introduction
Cd ect.) and main group elements (B, Al, Ga, In, etc.) have
been incorporated into the frameworks of these solid-state
materials, including phosphates and germanates.6 Of par-
ticular interest is that incorporation of transition metal
elements may lead to microporous materials with interesting
electrical and magnetic properties.7
In contrast to well-characterized vanadium phosphate
phases that display rich structural diversity, little research
has been carried out on the synthesis of niobium phosphate
analogues, which are usually prepared by solid-state
reactions8-15 or by high-temperature hydrothermal (g600 °C)
Microporous materials are of great interest because of their
rich structural chemistry and immense practical importance
for commercial applications such as catalysis, absorption,
separation, ion exchange, etc.1-4 While mathematical pos-
sibilities are numerous for these materials, the number of
topologies that can be realized in a chemical system is limited
because of the restriction by the availability of basic chemical
building units and their bonding requirements. The occur-
rence of microporous aluminophosphate5 in the 1980s spurred
widespread enthusiasm in the preparation of zeotype materi-
als, other than initial aluminosilicates, with novel framework
topologies or chemical compositions because the utility of
these crystalline materials is intimately correlated to their
geometrical features. To date, a very wide range of the
transition metals (Sc, Ti, Zr, V, Cr, Mn, Fe, Co, Ni, Cu, Zn,
(6) Cheetham, K.; Fe´rey, G.; Loiseau, T. Angew. Chem., Int. Ed. 1999,
38, 3268 and references therein.
(7) Cavellec, M.; Riou, D.; Fe´rey, G. Inorg. Chim. Acta 1999, 291, 317.
(8) Levin, E. M.; Roth, R. S. J. Solid State Chem. 1970, 2, 250.
(9) Linde, S. A.; Gorbunova, Y. E.; Lavrov, A. V.; Tananaev, I. V. Dokl.
Akad. Nauk SSSR 1980, 250, 96.
(10) Lavrov, V. IzV. Akad. Nauk SSSR, Neorg. Mater. 1982, 18, 996.
(11) Zid, M. F.; Jouini, T.; Jouini, N. C. R. Acad. Sci. Paris, Ser. I.i 1989,
309, 343.
(12) Leclaire, Borel, M. M.; Grandin, A.; Raveau, B. J. Solid State Chem.
1989, 80, 12.
(13) Raveau, Borel, M. M.; Leclaire, A.; Grandin, A. Int. J. Modern Phys.
1993, B7, 4109.
(14) Leclaire, Borel, M. M.; Chardon, J.; Raveau, B. J. Solid State Chem.
1994, 111, 26.
* To whom correspondence should be addressed. E-mail: ygy@
fjirsm.ac.cn. Fax: +86-591-8371-0051.
(1) Davis, M. E. Chem. Mater. 1992, 4, 756.
(2) Venuto, P. B. Microporous Mater. 1994, 2, 297.
(3) Barton, T. J.; Bull, L. M.; Klemperer, W. G.; Loy, D. A.; McEnaney,
B.; Misono, M.; Monson, P. A.; Pez, G.; Scherer, G. W.; Vartuli, J.
C.; Yaghi, O. M. Chem. Mater. 1999, 11, 2633.
(4) Davis, M. E. Nature 2002, 417, 813.
(5) Wilson, S. T.; Lok, B. M.; Messina, C. A.; Cannan, T. R.; Flanigen,
E. M. J. Am. Chem. Soc. 1982, 104, 1146.
(15) Fakhfakh, M.; Oyetola, S.; Jouini, N.; Verbaere, A.; Piffard, Y. Mater.
Res. Bull. 1984, 29, 97.
10.1021/ic061752i CCC: $37.00
Published on Web 12/13/2006
© 2007 American Chemical Society
Inorganic Chemistry, Vol. 46, No. 1, 2007 231

Liu et al.
reactions;16,17 this can be attributed to the difference of
chemical and physical characteristics between vanadium and
niobium. First, vanadium may exhibit various oxidation states
(from +3 to +5) and flexible coordination geometries (square
pyramidal, octahedral, tetrahedral, and trigonal bipyramidal),
whereas niobium usually exists with a valence of +5,
exhibiting in an octahedral coordination geometry.18,19 Sec-
ond, the very low solubility of niobium source from typical
commercial suppliers causes difficulties in the successful
synthesis of niobium-containing materials with high crystal-
linity. It has been shown recently by Jacobson et al.20 that
crystalline niobium phosphates can be synthesized using low-
temperature hydrothermal route, which is typically used for
the synthesis of zeolite microporous materials. Furthermore,
low-temperature hydrothermal reactions allow the use of
organic structure-directing agents and enhance the possibili-
ties for synthesizing new framework topologies. Unfortu-
nately, so far, only one example of zeotype niobium-
containing phosphates, [(Nb0.9V1.1)O2(PO4)2(H2PO4)](N2C2H10),
has been reported using organic amines as templates,20d the
structure of which is closely similar to the vanadium
phosphate analog (VO)2(PO4)2H2PO4‚N2C2H10.21
Recently, we exploit a pathway to the formation of
crystalline niobium phosphates with Nb2O5 as the niobium
source at relatively low temperature by a two-step hydro-
thermal process. As a part of our ongoing research, herein
we describe the syntheses, crystal structures, and thermal
properties of two organically templated niobium and zinco-
niobium fluorophosphates NbOF(PO4)2(C2H10N2)2 (1) and
Zn3(NbOF)(PO4)4(C2H10N2)2 (2) prepared hydrothermally
using ethylenediamine as the template. Compound 1 is the
first example of 1-D niobium phosphates templated by an
organic amine consisting of corner-sharing [Nb2P2] 4-MRs,
and compound 2, containing chain motifs similar to those
found in 1, form a 4-connected 3-D network with a new
zeolite framework topology.
crystals of 1 were recovered as the sole product of the reaction by
filtration; they were washed with water and allowed to dry in air.
The yield was greater than 95% based on Nb. Compound 2 was
synthesized following the same procedure using 0.591 g of
Zn(H2PO4)‚2H2O as the starting material instead of H3PO4. The
product, containing white polycrystalline powder and colorless
prismlike single crystals in a yield of about 70% based on niobium,
was separated by sonication and further washed by distilled water
and then air-dried. IR (KBr, cm-1): ν 3440s, 2917s, 2849s, 2728s,
2190m, 1642m, 1599m, 1553m, 1470w, 1355w, 1247w, 1098s,
1070s, 1021s, 982s, 914s, 880s, 799m, 635w, 587w, 554m, 539m,
489w, 452w for 1; 3444s, 3220s, 2918s, 1621s, 1524s, 1458w,
1415w, 1381w, 1345w, 1328w, 1084s, 1053s, 1009s, 935s, 852s,
644s, 576s, 550s, 471m for 2.
Analytical Procedures. Powder X-ray diffraction patterns
(PXRD) were collected with a PANalytical X’Pert Pro diffrac-
tometer using Cu KR radiation (λ ) 1.5418 Å). Qualitative energy-
dispersive spectroscopy (EDS) analyses of single crystals were
performed on a JEOL JSM6700F field-emission scanning electron
microscope equipped with a Oxford INCA system. Elemental
analyses of C, H, and N were performed on an Elemental Vario
EL III analyzer. Infrared spectra were recorded on an ABB Bomen
MB 102 series FT-IR spectrophotometer at room temperature over
the range of 4000-400 cm-1, using a sample powder pelletized
with KBr. The thermogravimetric analyses (TGA) were performed
on a Mettler Toledo TGA/SDTA 851e analyzer. The samples were
contained within alumina crucibles and heated at a rate of 10 °C
min-1 from 30 to 900 °C in dry flowing N2 (10 mL/min-1).
Single-Crystal X-ray Studies. Crystals of 1 (dimensions 0.20
× 0.18 × 0.18 mm) and 2 (dimensions 0.40 × 0.28 × 0.20 mm)
were selected for single-crystal analyses at room temperature. The
data was collected using a Bruker Smart CCD diffractometer with
graphite-monochromated Mo KR radiation (λ ) 0.71073 Å) over
the range of 2.27° e θ e 25.68° and 2.52° e θ e 25.73° for
compounds 1 and 2, respectively. Of 3776 and 5180 reflections,
2575 and 970 were independent for compounds 1 and 2, respec-
tively. Absorption corrections were based on symmetry-equivalent
reflections using the SADABS program.22 The structures were
solved by direct methods using the SHELXS program.23 The heavy
atoms (Nb, P, or Zn) were first revealed, and the remaining atoms
(O, C, N) were placed from successive Fourier map analyses. In
compound 1, all the hydrogen atoms of the protonated ethylene-
diamine molecular were geometrically idealized and allowed to ride
on their parent atoms; for compound 2, the hydrogen atoms of the
protonated ethylenediamine molecular were not totally fixed because
it is disordered in two equivalent positions, and the corresponding
carbon (C1) and nitrogen (N2) atoms have been refined with a 50%
site occupancy factor. Oddly, a moderately large C-N (1.622 Å)
distance is observed for the template molecule. This may reflect
the motion of the organic molecule within the cavities of the
structure. The refinements were performed using a full-matrix least-
squares analysis with anisotropic thermal parameters for all non-
hydrogen atoms. Crystallographic and refinement details are
summarized in Table 1. The final R indices for 2 are moderately
high probably because of the statistical disorder of organic amines
and poor crystal quality.
Experimental Section
Reagents. All reagents were of analytical grade and were used
without further purification.
Synthesis. Compounds 1 and 2 were synthesized using a two-
step hydrothermal technology in a 23 mL Teflon-lined autoclave.
In a typical synthesis of compound 1, 0.144 g of Nb2O5 was
dissolved in 0.288 g of 48 wt % HF and heated to 110 °C for 24
h. After it was cooled, this solution was combined with 85% H3PO4
(0.15 mL), ethylenediamine (en, 0.3 mL), H2O (4 mL), and ethylene
glycol (3 mL) and heated at 180 °C for 7 days. Colorless rodlike
(16) Longo, J. M.; Kierkegaard, P. Acta Chem. Scand. 1966, 20, 72.
(17) Liang, S.; Harrison, W. T. A.; Eddy, M. M.; Gier, T. E.; Stucky, G.
Chem. Mater. 1993, 5, 917.
(18) Pope, M. T. Heteropoly and Isopoly Oxometalates; Springer: New
Yark, 1983.
(19) Hagrman, P. J.; Finn, R. C.; Zubieta, J. Solid State Sci. 2001, 3, 745.
(20) (a) Wang, X.; Liu, L.; Cheng, H.; Jacobson, A. J. Chem. Commun.
1999, 2531. (b) Wang, X.; Liu, L.; Jacobson, A. J. J. Mater. Chem.
2000, 10, 2774. (c) Wang, X.; Liu, L.; Cheng, H.; Ross, K.; Jacobson,
A. J. J. Mater. Chem. 2000, 10, 1203. (d) Wang, X.; Liu, L.; Jacobson,
A. J. J. Mater. Chem. 2002, 12, 1824. (e) Wang, X.; Liu, L.; Jacobson,
A. J. J. Solid State Chem. 2004, 177, 194.
(22) Sheldrick, G. M. SADABS, A Program for the Siemens Area Detector
Absorption Correction; University of Go¨ttingen: Go¨ttingen, Germany.
1997.
(23) (a) Sheldrick, G. M. SHELXS97, Program for Solution of Crystal
Structure; University of Go¨ttingen: Go¨ttingen, Germany, 1997. (b)
Sheldrick, G. M. SHELXS97, Program for Solution of Crystal
Refinement; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(21) Harrison, W. T. A.; Hsu, K.; Jacobson, A. J. Chem. Mater. 1995, 7,
2004.
232 Inorganic Chemistry, Vol. 46, No. 1, 2007

NbOF(PO4)2(C2H10N2)2 and Zn3(NbOF)(PO4)4(C2H10N2)2
Table 1. Crystal and Structure Refinement Data for 1 and 2
1
2
empirical formula
fw
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg°)
V (Å3)
C4H20FN4NbO9P2
442.09
P-1
C4H20FN4NbO17P4Zn3
828.25
Fddd
9.1928(2)
14.2090(1)
32.2971(6)
90
8.1075(6)
9.8961(7)
10.1420(8)
111.655(1)
111.51(1)
93.206(1)
686.19(9)
2
90
90
4218.66(12)
8
2.608
6.482
3264
Z
d
calcd (g cm-3
)
2.140
1.175
448
µ(Mo KR) (mm-1
F(000)
)
θ range (deg)
R1 [I > 2σ(I)]a
wR2 [I > 2σ(I)]b
2.27-25.68
2.52-25.73
0.0798
0.1708
0.0461
0.1072
2
2
a R1
)
∑(|Fo|
-
|Fc|)/∑|Fo|. b wR2
)
{∑[w(|Fo|
-
|Fc| )2]/
2
∑[w(|Fo| )2]}1/2
.
Results and Discussion
Synthesis and Chemical Composition. Single crystals of
the compounds 1 and 2 were hydrothermally synthesized by
following similar procedures in the presence of ethylene-
diamines as structure-directing agents. The incorporations
of enH2 (diprotontized ethylenediamine) in the compounds
were confirmed by FT-IR spectra and subsequent single-
crystal structure refinements. Hydrofluoric acid not only
plays a key role of dissolving the starting reaction material
Nb2O5 but also subsequently takes part in the structure
constructions of the title compounds. The powder X-ray
diffraction patterns of the bulk products are in good agree-
ment with the calculated patterns based on the single crystal
solutions (Figure 1), indicating the phase purity of the
samples. Elemental analysis gives C, H, and N contents of
10.73, 4.38, and 12.61% (calcd C, 10.86; H, 4.52; N, 12.67%)
for compound 1, and 5.86, 2.58 and 6.84% (calcd C, 5.80;
H, 2.42; N, 6.76%) for compound 2, respectively. Energy
dispersive spectroscopy (EDS) gives the Nb/P/F ratio as 1.0:
2.1:1.2 (calcd 1:2:1) for compound 1 and the Nb/Zn/P/F ratio
as 1:2.9:4.2:1.3 (calcd 1:3:4:1) for compound 2. These results
are in agreement with their respective formulas found from
the single crystal analyses.
Figure 1. Simulated and experimental powder X-ray diffraction patterns
of compounds 1 (a) and 2 (b).
Figure 2. ORTEP plot of the asymmetric unit showing the local
coordination environments of cations in compound 1, with the symmetry-
related part drawn as open circles. Thermal ellipsoids are given at 30%
probability.
Crystal Structures. The asymmetric unit of 1 (Figure 2)
contains one crystallographically distinct Nb site and two
unique P sites. The Nb atom is octahedrally coordinated, and
the P atoms are all tetrahedrally coordinated. The four
equatorial oxygen atoms of the Nb octahedron with Nb-O
bond lengths of 1.987(4)-2.041(4) Å are shared by four
phosphate tetrahedra; the two apical positions of the octa-
hedron are completed by a short terminal NbdO bond of
1.736(4) Å and a weak terminal Nb-F bond of 2.133(3) Å.
Notably, the geometrical parameters of the distorted NbO5F
octahedron are very close to that of geometry-optimized
[NbOF5]2- (1.771 Å for NbdO and 2.129 Å for trans-Nb-
F)24 and known niobium oxyfluorides.24,25,26 Bond valences
calculated27 for the apical NbdO and Nb-F bonds of the
octahedron are 1.60 and 0.43 valence units, respectively.
Similar lower values are commonly found in niobium
oxyfluorides such as [NbOF(PO4)](N2C5H7) (1.25 for NbdO,
0.74 for Nb-F)20d and [4-apyH]2[Cu(4-apy)4(NbOF5)2] (1.63
for NbdO, 0.45 for trans-Nb-F),25 suggesting that strong
hydrogen bonds are formed between the guest cations and
two terminal anions (see below). P(1) and P(2) each share
two oxygen atoms with adjacent Nb atoms with P-O bond
lengths in the range of 1.551-1.562 Å, leaving two terminal
oxygen groups with shorter PdO bond lengths between 1.508
and 1.526 Å. The P-O and PdO bond lengths are in good
agreement with those reported for similar compounds in the
literature.28,29
(24) Welk, M. E.; Norquist, A. J.; Arnold, F. P.; Stern, C. L.; Poeppelmeier,
K. R. Inorg. Chem. 2002, 41, 5119.
(25) Izumi, H. K.; Kirsch, J. E.; Stern, C. L.; Poeppelmeier, K. R. Inorg.
Chem. 2005, 44, 884.
(26) Heier, K. R.; Norquist, A. J.; Wilson, C. G.; Stern, C. L.; Poeppelmeier,
K. R. Inorg. Chem. 1998, 37, 76 and references therein.
(27) Brown, I. D.; Altermatt, D. Acta Crystallogr., Sect. B 1985, 41, 244.
(28) Natarajan, S. Inorg. Chem. 2002, 41, 5530.
Inorganic Chemistry, Vol. 46, No. 1, 2007 233

Liu et al.
Figure 3. Views of the structure of 1 (a) along the [1 0 0] direction and
(b) along the [0 0 1] direction: PO4, yellow tetrahedra; NbO5F, purple
octahedra.
Figure 4. ORTEP plot of the asymmetric unit showing the local
coordination environments of cations in compound 2, with the symmetry-
related part drawn as open circles. Thermal ellipsoids are given at 30%
probability.
The inorganic host of 1 is an infinite anionic chain running
along the [001] direction with corner-sharing [Nb2P2] 4-MRs
bridged at the Nb centers (Figure 3a). Sch a 1-D chain
constructed by corner-sharing 4-MRs can be observed in
several metal phosphates such as gallophosphates29 and iron
phosphates.30 Similar chains totally based on tetrahedral metal
sites are ubiquitous in the phosphate system28,31-37 and can
be found as the building bock in some layered or 3-D
O/F bond length of 1.924(12) Å. The disordered terminal
sites on NbO5F octahedra are typical for niobium oxy-
fluorides,20d,42,43 similar to the [NbOF5]2- cases where the
anions conform to the centricity of the crystal lattice.25,26,44
These are also in accordance with the discussions on the
distortion of the niobium octahedron (see below). The Zn
and P atoms are tetrahedrally coordinated with the Zn-O
bond lengths in the range of 1.935(9)-1.944(8) Å and the
P-O bond distances between 1.506(9) and 1.571(10) Å. The
average O-T-O angles are 109.7(4) and 109.1(7)° for ZnO4
and PO4, respectively, typical for tetrahedral geometries.
Bond valence sums27 for all unique atoms were calculated
and are in good accordance with their formal oxidation states
except for that of the disordered terminal anion on the
niobium octahedron. The lower value calculated for the
terminal atom (0.76 for F and 0.97 for O) seems to show
that the anion is a hydroxyl; however, the Nb-O/F bond
length of 1.924(12) Å is not uncommon in niobium phos-
phates containing similar disordered NbO5F octahedra20d,43
and niobium oxyfluorides containing [NbOF5]2- anions.24-26
In addition, energy-dispersive spectroscopy (EDS) shows that
2 contains the F atom. Therefore, the terminal atom was
assigned as disordered O/F atom, not an OH group. Charge-
balancing criterion confirmed that this assignment is reason-
able.
2-
phosphates.38-41 The chains of composition NbOF(PO4)2
are separated by charge-balancing enH2 cations. In the [001]
projection, each inorganic chain is surrounded by six enH2
stacks, in turn, each of which is surrounded by three
inorganic chains (Figure 3b). There is extensive hydrogen
bonding between the N atoms of enH2 cations and O/F atoms
in the inorganic chains with bond distances of N‚‚‚O )
2.709(6)-3.157(6) Å and N‚‚‚F ) 2.736(6)-3.184(6) Å,
respectively.
The asymmetric unit of 2 (Figure 4) contains one crys-
tallographically distinct Nb atom that lies at a site with D2
crystallographic symmetry, two distinct Zn atoms, of which
Zn(1) also lies at a site with D2 crystallographic symmetry
and Zn(2) resides on the twofold symmetry axis, and a unique
P atom in general position. The Nb atom is octahedrally
coordinated, sharing four equatorial oxygen atoms with
adjacent P atoms, with uniform Nb-O bond of 1.983(8) Å.
The two apical corners of the octahedron are randomly
occupied by terminal fluorine and oxygen atoms with a Nb-
There are only Nb-O-P and Zn-O-P linkages in the
framework of 2. The basis of the structure is an infinite linear
chain along the [100] direction, which is similar to that in 1
except that one-half of the 4-connected Nb octahedra are
substituted alternately by Zn(1)O4 tetrahedra. The fully
4-connected 3-D network of 2 is completed by cross-linking
between six Zn(2)O4 tetrahedra stacks along the [100]
direction and by connection of each infinite linear chain via
sharing oxygen atoms (Figure 5). Each Zn(2)O4 tetrahedra
is corner-shared with four P tetrahedra from adjacent three
corner-sharing chains, of which two are from the same chain
and the other two are from different chains; such connections
leads to new types of 1-D zigzag chains constructed by side-
sharing 4-MRs. These side-sharing chains propagate parallel
(29) Walton, R. I.; Millange, F.; Bail, A. L.; Loiseau, T.; Serre, C.; O’Hare,
D.; Fe´rey, G. Chem. Commun. 2000, 203.
(30) Cavellec, M.; Riou, D.; Grenee`he, J.; Fe´rey, G. Inorg. Chem. 1997,
36, 2187.
(31) Loiseau, T.; Serpaggi, F.; Fe´rey, G. Chem. Commun. 1997, 1093.
(32) Rao, C. N. R.; Natarajan, S.; Neeraj, S. J. Am. Chem. Soc. 2000, 122,
2810.
(33) Chiang, R. J. Solid State Chem. 2000, 153, 180.
(34) Wang, K.; Yu, J.; Li, C.; Xu, R. Inorg. Chem. 2003, 42, 4597.
(35) Yu, J.; Sugiyama, K.; Hiraga, K.; Togashi, N.; Terasaki, O.; Tanaka,
Y.; Nakata, S.; Qui, S.; Xu, R. Chem. Mater. 1998, 10, 3636.
(36) Huo, Q.; Xu, R.; Li, S.; Ma, Z.; Thomas, J. M.; Jomes, R. H.;
Chippindale, A. M.; Chem. Commun. 1992, 875.
(37) Chen, P.; Li, J.; Yu, J.; Wang, Y.; Pan, Q.; Xu, R. J. Solid State Chem.
2005, 178, 1929.
(38) Oliver, S.; Kuperman, A.; Ozin, G. A. Angew. Chem., Int. Ed. 1998,
37, 46.
(39) Yu, J.; Xu, R. Acc. Chem. Res. 2003, 36, 481.
(40) Jones, R. H.; Thomas, J. M.; Xu, R.; Huo, Q.; Xu, Y.; Cheetham, A.
K.; Bieber, D. Chem. Commun. 1990, 1170.
(41) (a) Williams, I. D.; Yu, J.; Gao, Q.; Chen, J.; Xu, R. Chem. Commun.
1997, 1273. (b) Ayi, A. A.; Choudhury, A.; Natarajan, S. J. Solid
State Chem. 2001, 156, 185. (c) Wang, K.; Yu, J.; Song, Y.; Xu, R.
Dalton Trans. 2003, 99. (d) Wei, B.; Yu, J.; Shi, Z.; Qiu, S.; Yan,
W.; Terasaki, O. Chem. Mater. 2000, 12, 2065.
(42) Francis, R. J.; Jacobson, A. J. Chem. Mater. 2001, 13, 4676.
(43) Liu, G.-Z.; Zheng, S.-T.; Yang, G.-Y., Chem. Commun. 2006, in press
(DOI:10.1039/B614265F).
(44) Halasyamani, P. S.; Heier, K. R.; Norquist, A. J.; Stern, C. L.;
Poeppelmeier, K. R. Inorg. Chem. 1998, 37, 369.
234 Inorganic Chemistry, Vol. 46, No. 1, 2007

NbOF(PO4)2(C2H10N2)2 and Zn3(NbOF)(PO4)4(C2H10N2)2
Figure 6. (a) [4684] cage encapsulating an ethylenediamine in 2. Oxygen
atoms and the disordered parts of ethylenediamine are omitted for clarity.
(b) Net (6‚6‚6‚62‚62‚62) of [4684]] cage centers in 2 related to diamond net
(62‚62‚62‚62‚62).
Figure 5. 3-D host framework of 2 viewed along the [1 0 0] direction:
PO4, yellow tetrahedra; ZnO4, green tetrahedra; NbO5F, purple octahedra.
to the crystallographic [1 1 0], [1 -1 0], [0 1 1] and [0 -1 1]
directions and are cross-linked to the corner-sharing 4-MRs
chains. According to the aufbau principle of building
higher-D structures from that of the lower-D ones,45 wherein
the 0-D, especially 4-MRs, and the 1-D structures are
considered to be synthons of the more complex structures.
It is conceivable that the 3-D framework of 2 can be
considered to result from the progressive reassembly of the
4-MRs or the resulting 1-D chain precursor observed in 1
through Zn2+ cations, considering their similar synthetic
conditions. One of notable examples is an aluminophosphate
NiAlP2O8‚C2N2H9, assembled by a transformation mecha-
nism of “chain-to-chain-3-D framework” so that the edge-
sharing 4-MR chains first transform to the corner-sharing
4-MR chains and then assemble to 3-D open framework
through Ni2+ cations.34
Figure 7. Framework topology of 2 along the [1 0 0] direction: P, yellow;
The resulting 3-D framework of 2 contains multidirectional
interpenetrated channels that appear to have 4- and 8-MR
openings. Figure 5 shows the 8-MR channels along the
[1 0 0] direction. In addition, there are also other 8-MR
channels along the [2 1 1], [2 -1 1], [2 1 -1], [-2 1 1],
[1 1 0], and [-1 1 0] directions. Thus, 2 has a multidirectional
pore system.
Zn, green; Nb, purple.
The network of 2 is closely related to that of the zeolite
gismondine (GIS topology),46 in that it possesses only 4-
and 8-MRs and generates a 3-D channel system with
gismondine-type [4684] cavities (Figure 6a) at each channel
intersection. The framework topology of zeolite gismondine
can be simply considered as a periodic diamond-type array
of the [4684] cavities, in which the centers of the cavities sit
on the nodes of diamond net (62‚62‚62‚62‚62),47 whereas the
network of 2 is a novel periodic array of the [4684] cavities
based on net (6‚6‚6‚62‚62‚62) (Figure 6b),48 which is closely
related to the diamond net and both nets can be readily
intergrown. In fact, compound 2 has a previously unknown
framework topology (Figure 7) with the vertex symbol 4‚
4‚4‚4‚8‚8 (vertex 1), 4‚4‚4‚82‚8‚8 (vertex 2), 4‚4‚8‚8‚82‚82
(vertex 3), and 4‚4‚4‚82‚8‚8 (vertex 4). In addition, it is
Figure 8. Three types of T-atom loop configurations observed in the 2
framework topology. The loop configuration is a simple graph showing
how many 3- or 4-membered rings a given T-atom is involved in. In 2,
with four crystallographically unique T-atoms including two unique Zn
atoms adopting the a and b configurations shown here, one unique P atom
adopting the b type, and one unique Nb atom adopting the c type.
noticeable that three types of loop configurations (Figure 8)
are found in the 2 framework topology, one of which (Figure
8a) is extremely rare in 4-connected structures and only
occurs in the zeolite CZP framework type.46 The new
framework topology was predicted by Wiebcke;47 he de-
scribed a (3,4)-connected zincophosphate of [Zn3(HPO4)4]-
(NMe4)2 with interrupted 2 topology, which may be consid-
ered to be a 2 framework structure with local interruptions
on the Nb sites to produce four terminal P-OH groups
surrounding each vacant tetrahedral site. In other words, the
(3,4)-connected network can be derived from the 4-connected
network of 2 by removing one-eighth of all of the tetrahedral
nodes. Other related cases are three examples of (3,4)-
connected zincophosphites, templated by (CH3)4N+,
(45) Rao, C. N. R.; Natarajan, S.; Choudhury, A.; Neeraj, S.; Ayi, A. A.
Acc. Chem. Res. 2001, 34, 80.
(46) Baerlocher, C.; Meier, W. M.; Olson, D. H. Atlas of Zeolite Framework
Types; Elsevier: Amsterdam, 2001; http://www.iza-structure.org/
databases.
(47) Wiebcke, M. J. Mater. Chem. 2002, 12, 421.
(48) O’Keeffe, M.; Breese, N. E. Acta Crystallogr., Sect A 1992, 48, 663.
(CH3)3NH+, and (CH3)2NH2 respectively, with similar
+
Inorganic Chemistry, Vol. 46, No. 1, 2007 235

Liu et al.
Table 2. Features of the [NbOF5]2-, [NbO5F]6-, and [NbO2F4]3- Octahedra in Particular Structures
features of niobium octahedra
types of
octahedra
NbdO
(Å)
trans-Nb-F
origin of
distortion
direction of
primary distortion
bridging
atoms
compounds
ref
(Å)
[4-apyH]2[Cu(4-apy)4(NbOF5)2]
Cd(3-apy)4NbOF5
[NbOF5]2-
[NbOF5]2-
25
25
1.730(3)
1.914(3)
2.118(2)
1.937(3)
SOJTa
apical O atom
apical O atom
apical O atom
SOJT bond
networks
SOJT bond
networks
SOJT bond
networks
none found
none found
SOJT
apical O, F atom
apical O atom
apical O atom
[HNC6H6OH]2[Cu(py)4(NbOF5)2]
[pyH]2[Cu(py)4(NbOF5)2]
[NbOF5]2-
[NbOF5]2-
24
55
1.763(1)
1.728(8)
2.098(1)
2.099(8)
apical O atom
apical O atom
Cu(3-apy)4NbOF5
Na13Nb3P6O28F2
Compound 1
Compound 2
(C2H10N2)2[Nb2O3F8]
[NbOF5]2-
[NbO5F]6-
[NbO5F]6-
[NbO5F]6-
[NbO2F4]3-
25
43
this work
this work
56
1.919(1)
1.932(7)
1.736(4)
1.924(12)
1.766/1.736
1.919(1)
1.932(7)
2.133(3)
1.924(12)
2.097/2.061
none found
none found
apical O atom
none found
side (O-O)
apical O, F atom
equatorial O atom
equatorial O atom
equatorial O atom
one of O atoms
none found
SOJT bond
networks
1.906/1.936
2.172/1.982
a Second-order Jahn-Teller effects.
interrupted 2 topology.49 In these structures, the distribution
of four P-H groups adopts the tetrahedral pattern surround-
ing a vacant tetrahedral node. The centroid of these four
phosphorus positions would correspond to the position of
missing tetrahedral nodes.
+
Compared with the NMe4 cation, which is well-known
to direct the formation of small cavities,50 the enH2 cation
encapsulated in the [4684] cavity of 2 is disordered because
the special site of the molecule and because the hydrogen
atoms could not be located. Despite this, it seems that
hydrogen-bonding interactions exist between the enH2 cation
and the oxygen atoms of the framework through a plethora
of short N‚‚‚O separations between 2.823 and 3.248 Å.
Distortion of Niobium Octahedra. The out-of-center
distortions for octahedrally coordinated early d0 transition
metals are very common and can be understood on the basis
of the second-order Jahn-Teller effect (electronic effect).51-53
Other secondary distortions, such as the bond-network effect,
lattice stresses, and cation-cation repulsions, work together
symbiotically to stabilize the distortions in mixed-metal
oxides.54
However, in NbOxF6-x (x ) 1 or 2) octahedra, only the
filled p orbitals of the oxide ligands can mix with vacant
cation d orbitals because the energy of the fluoride p orbitals
is too low for any significant mixing to occur. The result is
a spontaneous distortion of the central niobium cation toward
each oxide ligand.24 The primary distortion is inherent to
the oxyfluoride anions and is not dependent on the extended
crystal structure, and the direction of this distortion can be
a corner (x ) 1) or edge (x ) 2) of the octahedron, depending
on the number of oxide ligands.
Figure 9. TGA curves of 1 and 2.
network interactions (including hydrogen bonding) around
the anion occur asymmetrically.24,25,55 For the NbO5F octa-
hedron in 1, the shortening of the apical Nb-O bond and
lengthening of the trans-Nb-F bond is similar to that for
the [NbOF5]2- anion; nevertheless, the approximately sym-
metrical bond networks about the octahedron causes sym-
metrical lengthening and shortening of bonds making
detection of a secondary distortion impossible. Furthermore,
it is notable that the crystallographic disorders in the apical
positions can lead to the acentric [NbOF5]2- anion and
NbO5F octahedron occupying a center of inversion in the
crystal structures in the expense of its distortion, as shown
in 2 and other similar niobium oxyfluorides.20c,25 In addition,
the unique cis-NbO2F4 octahedron is found in the dimer
(C2H10N2)2[Nb2O3F8],56 where the primary distortion results
in a slight displacement of the niobium center cation toward
an edge (O-O), and incidentally, bond-network effects
modify the primary distortion. Table 2 shows a concise
comparison of the [NbOF5]2-, [NbO5F]6-, and [NbO2F4]3-
octahedral distortions based on the structures described here.
Thermal Analysis. The thermal analysis (Figure 9) of 1
reveals a weight loss of 23.64% between 270 and 400 °C,
followed by a further weight loss of 14.23% between 400
and 880 °C. The calculated total weight loss (37.83%),
For the [NbOF5]2- anion, the primary distortion results in
a short apical NbdO bond and a long trans-Nb-F bond,
and a secondary distortion can also be observed when bond-
(49) Chen, L.; Bu, X. Inorg. Chem. 2006, 45, 4654.
(50) Baerlocher, C.; Meier, W. M. HelV. Chim. Acta 1970, 53, 148.
(51) Burdett, J. K. Molecular Shapes; Wiley-Interscience: New York. 1980.
(52) Wheeler, R. A.; Whangbo, M. H.; Hughbanks, T.; Hoffmann, R.;
Burdett, J. K.; Albright, T. A. J. Am. Chem. Soc. 1986, 108, 2222.
(53) Kang, S. K.; Tang, H.; Albright, T. A. J. Am. Chem. Soc. 1993, 115,
1971.
(55) Halasyamani, P.; Willis, M. J.; Stern, C. L.; Lundquist, P. M.; Wong,
G. K.; Poeppelmeier, K. R. Inorg. Chem. 1996, 35, 1367.
(54) Kunz, M.; Brown, I. D. J. Solid State Chem. 1995, 115, 395.
(56) Nicholas, F. S.; Philip, L. Acta Crystallogr., Sect. C 2005, 61, m344.
236 Inorganic Chemistry, Vol. 46, No. 1, 2007

NbOF(PO4)2(C2H10N2)2 and Zn3(NbOF)(PO4)4(C2H10N2)2
corresponding to 1.5 H2O (6.11%) and one HF (4.52%), as
well as combustion of two ethylenediamine molecules
(27.19%) per formula unit by assuming a residual composi-
tion of 1/2Nb2O5‚P2O5, is in agreement with the observed
values. The TGA data for 2 shows that the compound is
stable up to ∼380 °C and subsequently decomposes to lose
two ethylenediamines (14.51%), 1.5 H2O (3.26%), and one
HF (2.41%) per formula unit. The marked weight loss of
20.16% up to 900 °C agrees with the calculated value of
20.18% by assuming that the final product is mixture of
3ZnO‚1/2Nb2O5‚2P2O5.
by additional ZnO4 tetrahedra to produce a 4-connected 3-D
network with a previously unknown framework topology. It
is suggested that compound 1 may be thought of as a solid
precursor to compound 2, and we are investigating its
possible transformation to other related niobium fluorophos-
phates, by the addition of other cations to further confirm
the validity of our speculation. In addition, considering the
large variety of organic templates that could be used in this
synthetic regime, it is possible to isolate other open-
framework niobium-based phosphates.
Acknowledgment. This work was supported by the
NNSF of China (Nos. 20473093 and 20271050), the Talents
Program of the Chinese Academy of Sciences, the NSF of
Fujian Province (No. E0510030), and the State Important
Scientific Research Program (No. 2006CB932904).
Conclusion
A two-step hydrothermal process was employed to syn-
thesize two organically templated niobium and zinconiobium
fluorophosphates using ethylenediamine as the template. The
inorganic host of 1 is characterized by an infinite anionic
chain consisting of corner-sharing 4-MRs, and the structure
of 2 is based on infinite linear chains similar to that of 1,
except one-half of NbO5F octahedra are substituted alter-
nately by ZnO4 tetrahedra, which are further cross-linked
Supporting Information Available: Crystallographic informa-
tion in CIF format for compounds 1 and 2. This material is available
free of charge via the Internet at http://pubs.acs.org.
IC061752I
Inorganic Chemistry, Vol. 46, No. 1, 2007 237