New d0 transition metal iodates: Synthesis, structure, and characterization of BaTi(IO3)6, LaTiO(IO3) 5, Ba2VO2(IO3)4· (IO3), K2MoO2(IO3)4, and BaMoO2(IO3)4·H2O

Article abstract of DOI:10.1021/ic048428c

Five new d⁰ transition metal iodates, BaTi(IO₃) ₆, LaTiO(IO₃)₅, Ba₂VO ₂(IO₃)₄·(IO₃), K ₂MoO₂(IO₃)₄, and BaMoO ₂(IO₃)₄· H₂O, have been synthesized by hydrothermal methods using Ba(OH)₂·8H ₂O, La₂O₃, K₂CO₃, TiO₂, V₂O₅, MoO₃, and HIO ₃ as reagents. The structures of these compounds were determined by single-crystal X-ray diffraction. All of the reported materials have zero-dimensional or pseudo-one-dimensional crystal structures composed of MO₆ (M = Ti⁴⁺ , V⁵⁺, or Mo⁶⁺) octahedra connected to IO₃ polyhedra. Infrared and Raman spectroscopy, thermogravimetric analysis, and UV-vis diffuse reflectance spectroscopy are also presented. Crystal data: BaTi(IO₃)₆, trigonal, space group R-3 (No. 148), with a = b = 11.4711(10) A, c = 11.1465(17) A, V = 1270.2(2) A³, and Z = 3; LaTiO(IO ₃)₅, monoclinic, space group P2₁/n (No. 14), with a = 7.4798(10) A, b = 18.065(2) A, c = 10.4843(14) A, β = 91.742(2)°, V = 1416.0(3) A³, and Z = 4; Ba ₂VO₂(IO₃)₄·(IO₃), monoclinic, space group P2₁/c (No. 14), with a = 7.5012(9) A, b = 33.032(4) A, c = 7.2150(9) A, β = 116.612(2)°, V = 1598.3(3) A³, and Z = 4; K₂MoO₂(IO ₃)₄, monoclinic, space group C2/c (No. 15), with a = 12.959(2) A, b = 6.0793(9) A, c = 17.748(3) A, β = 102.410(4)°, V = 1365.5(4) A³, and Z = 4; BaMoO ₂(IO₃)₄·H₂O, monoclinic, space group P2₁/n (No. 14), with a = 13.3368(17) A, b = 5.6846(7) A, c = 18.405(2) A, β = 103.636(2)°, V = 1356.0(3) A³, and Z = 4.

Full text of DOI:10.1021/ic048428c

Inorg. Chem. 2005, 44, 2263−2271
0
New d Transition Metal Iodates: Synthesis, Structure, and
Characterization of BaTi(IO ) , LaTiO(IO ) , Ba VO (IO ) (IO3),
‚
3 4
3
6
3 5
2
2
K MoO (IO ) , and BaMoO (IO ) ‚H O
2
2
3 4
2
3 4
2
Kang Min Ok and P. Shiv Halasyamani*
Department of Chemistry and Center for Materials Chemistry, 136 Fleming Building,
UniVersity of Houston, Houston, Texas 77204-5003
Received November 8, 2004
0
Five new d transition metal iodates, BaTi(IO
3
)
6
, LaTiO(IO
3
)
5
, Ba
2
VO
2
(IO
3
)
‚
4
‚
(IO
3
), K
2
MoO
, K
2
(IO
3
)
4
, and BaMoO
2 3 4
(IO ) ‚
H
2
O, have been synthesized by hydrothermal methods using Ba(OH)
and HIO
of the reported materials have zero-dimensional or pseudo-one-dimensional crystal structures composed of MO
Ti4+, V5+, or Mo6+) octahedra connected to IO
polyhedra. Infrared and Raman spectroscopy, thermogravimetric
2
8H O, La
2
2
O
3
2
CO
3
, TiO , V , MoO ,
2
2
O
5
3
3
as reagents. The structures of these compounds were determined by single-crystal X-ray diffraction. All
6
(M
)
3
analysis, and UV
group R-3 (No. 148), with a
monoclinic, space group P2
−
vis diffuse reflectance spectroscopy are also presented. Crystal data: BaTi(IO
3
)
)
6
, trigonal, space
3; LaTiO(IO
10.4843(14) Å, â )
/c (No. 14), with a
4; K MoO (IO
17.748(3) Å, â ) 102.410-
/n (No. 14), with a 13.3368-
4.
3
)
b
)
11.4711(10) Å, c
)
11.1465(17) Å, V
)
1270.2(2) Å , and Z
3 5
) ,
1
3
/n (No. 14), with a
)
7.4798(10) Å, b
)
18.065(2) Å, c
)
1
9
1.742(2)
°
, V
)
1416.0(3) Å , and Z
33.032(4) Å, c
)
2
4; Ba VO
2
(IO
3
)
4
‚(IO
3
), monoclinic, space group P2
)
) ,
3 4
3
7.5012(9) Å, b
)
)
7.2150(9) Å, â ) 116.612(2)
°
, V
)
1598.3(3) Å , and Z
)
2
2
monoclinic, space group C2/c (No. 15), with a
)
12.959(2) Å, b
)
6.0793(9) Å, c )
3
(4)°, V
)
1365.5(4) Å , and Z
)
)
4; BaMoO
2
(IO
)
3 4
2
‚H O, monoclinic, space group P2
1
)
3
(17) Å, b
)
5.6846(7) Å, c
18.405(2) Å, â ) 103.636(2)
°
, V
)
1356.0(3) Å , and Z
)
Introduction
whereas with the lone pair cation a nonbonded electron pair
is observed on the cation that “pushes” away the oxide
In oxide materials, cationic distortions are the driving force
for a host of technologically important physical properties
such as ferroelectricity, piezoelectricity, and second-harmonic
generation. Two families of cations are commonly observed
9
-17
7,18
ligands.
As previously discussed, these cationic dis-
placements can be described as primary distortions. Second-
ary distortions also occur and are defined as the interaction
0
between the d transition metal octahedron and the lone pair
0
in distorted oxide environments, octahedrally coordinated d
cation polyhedron. We recently reviewed all of the oxide
4+
5+
6+
transition metals (Ti , Nb , W , etc.) and lone pair cations
0
materials that contain octahedrally coordinated d transition
4+
4+
5+
(
Se , Te , I , etc.). With both families, second-order
metals and lone pair cations and made a number of
Jahn-Teller (SOJT) type distortions are thought to be the
cause for the cationic displacement.
coordinated d transition metals, the cationic distortion can
occur along an edge (local C
1-7
For octahedrally
(
8) Goodenough, J. B. Annu. ReV. Mater. Sci. 1998, 28, 1.
0
(9) Sidgwick, N. V.; Powell, H. M. Proc. R. Soc. London 1940, A176,
1
53.
2
direction), face (local C
3
8
(
(
(
10) Gillespie, R. J.; Nyholm, R. S. Q. ReV., Chem. Soc. 1957, 11, 339.
11) Orgel, L. J. Chem. Soc. 1959, 3815.
12) Lefebvre, I.; Lannoo, M.; Allan, G.; Ibanez, A.; Fourcade, J.; Jumas,
J. C. Phys. ReV. Lett. 1987, 59, 2471.
(13) Lefebvre, I.; Szymanski, M. A.; Olivier-Fourcade, J.; Jumas, J. C.
Phys. ReV. B 1998, 58, 1896.
direction), or corner (local C direction) of the octahedron,
4
*
Author to whom correspondence should be addressed. E-mail: psh@
uh.edu.
(
(
(
(
(
(
1) Opik, U.; Pryce, M. H. L. Proc. R. Soc. London 1957, A238, 425.
2) Bader, R. F. W. Mol. Phys. 1960, 3, 137.
3) Bader, R. F. W. Can. J. Chem. 1962, 40, 1164.
4) Pearson, R. G. J. Am. Chem. Soc. 1969, 91, 4947.
5) Pearson, R. G. J. Mol. Struct. (THEOCHEM) 1983, 103, 25.
6) Wheeler, R. A.; Whangbo, M.-H.; Hughbanks, T.; Hoffmann, R.;
Burdett, J. K.; Albright, T. A. J. Am. Chem. Soc. 1986, 108, 2222.
7) Kunz, M.; Brown, I. D. J. Solid State Chem. 1995, 115, 395.
(14) Watson, G. W.; Parker, S. C. J. Phys. Chem. B 1999, 103, 1258.
(15) Watson, G. W.; Parker, S. C.; Kresse, G. Phys. ReV. B 1999, 59, 8481.
(16) Seshadri, R.; Hill, N. A. Chem. Mater. 2001, 13, 2892.
(17) Waghmare, U. V.; Spaldin, N. A.; Kandpal, H. C.; Seshadri, R. Phys.
ReV. B 2003, 67, 125111-1.
(18) Welk, M. E.; Norquist, A. J.; Arnold, F. P.; Stern, C. L.; Poeppelmeier,
K. R. Inorg. Chem. 2002, 41, 5119.
(
1
0.1021/ic048428c CCC: $30.25
© 2005 American Chemical Society
Inorganic Chemistry, Vol. 44, No. 7, 2005 2263
Published on Web 03/08/2005

Ok and Halasyamani
Table 1. Crystallographic Data for BaTi(IO3)6, LaTiO(IO3)5, Ba2VO2(IO3)4·(IO3), K2MoO2(IO3)4, and BaMoO2(IO3)4‚H2O
formula
fw
space group
a (Å)
b (Å)
c (Å)
BaTi(IO3)6
1234.64
R-3 (No. 148)
11.4711(10)
11.4711(10)
11.1465(17)
90
90
120
1270.2(2)
3
LaTiO(IO3)5
1077.31
P21/n (No. 14)
7.4798(10)
18.065(2)
10.4843(14)
90
91.742(2)
90
1416.0(3)
4
Ba2VO2(IO3)4‚(IO3)
1232.12
P21/c (No. 14)
7.5012(9)
33.032(4)
7.2150(9)
90
116.612(2)
90
1598.3(3)
4
K2MoO2(IO3)4
905.74
BaMoO2(IO3)4‚H2O
980.88
C2/c (No. 15)
12.959(2)
6.0793(9)
17.748(3)
90
102.410(4)
90
1365.5(4)
4
P21/n (No. 14)
13.3368(17)
5.6846(7)
18.405(2)
90
103.636(2)
90
1356.0(3)
4
R (deg)
â (deg)
γ (deg)
3
V (Å )
Z
T (°C)
293.0(2)
0.71073
4.842
13.811
0.0221
293.0(2)
0.71073
5.054
14.528
0.0286
293.0(2)
0.71073
5.120
15.192
0.0369
293.0(2)
0.71073
4.406
10.684
0.0269
293.0(2)
0.71073
4.805
12.996
0.0274
λ (Å)
Fcalcd (g cm-3)
-
1
µ (mm
)
a
R(F)
2
b
Rw(Fo )
0.0580
0.0758
0.0848
0.0674
0.0616
a
b
2
2 -
2 2
2 2 1/2
R(F) ) ∑||Fo| - |Fc||/∑|Fo|. Rw(Fo ) ) [∑w(Fo
Table 2. Selected Bond Distances (Å) for BaTi(IO3)6, LaTiO(IO3)5, Ba2VO2(IO3)4·(IO3), K2MoO2(IO3)4, and BaMoO2(IO3)4‚H2O
BaTi(IO3)6 LaTiO(IO3)5 Ba2VO2(IO3)4‚(IO3) K2MoO2(IO3)4 BaMoO2(IO3)4‚H2O
I(1)-O(1) I(1)-O(1)
Fc ) /∑w(Fo ) ] .
I(1)-O(1)
1.791(5)
1.858(5)
1.808(5)
1.939(5)
1.839(5)
1.831(5)
1.802(5)
1.812(5)
1.826(5)
1.794(5)
1.819(5)
1.820(5)
1.801(5)
1.878(5)
1.806(5)
1.789(5)
1.803(5)
1.823(5)
1.815(5)
2.038(5)
2.117(5)
1.970(5)
2.042(5)
1.695(5)
1.987(5)
1.816(7)
1.844(6)
1.808(7)
1.832(7)
1.797(7)
1.809(7)
1.794(6)
1.866(6)
1.802(7)
1.816(7)
1.802(7)
1.788(7)
1.822(6)
1.796(7)
1.784(7)
1.975(6)
2.245(7)
1.975(6)
2.164(7)
1.639(7)
1.646(7)
I(1)-O(1)
I(1)-O(2)
1.912(4)
1.828(4)
2.337(4)
1.794(4)
1.840(4)
1.798(4)
1.784(4)
1.955(4)
2.238(4)
1.710(4)
I(1)-O(1)
I(1)-O(2)
1.813(4)
1.884(4)
1.786(4)
1.897(4)
1.807(4)
1.779(4)
1.846(4)
1.805(4)
1.788(4)
1.848(4)
1.797(4)
1.784(4)
1.962(4)
2.006(4)
2.196(4)
2.191(4)
1.709(4)
1.699(4)
I(1)-O(2)
I(1)-O(2)
I(1)-O(4)
I(2)-O(5)
I(2)-O(6)
I(2)-O(7)
I(3)-O(8)
I(3)-O(9)
I(3)-O(10)
I(4)-O(3)
I(4)-O(11)
I(4)-O(12)
I(5)-O(14)
I(5)-O(15)
I(5)-O(16)
Ti(1)-O(1)
Ti(1)-O(3)
Ti(1)-O(6)
Ti(1)-O(9)
Ti(1)-O(13)
Ti(1)-O(15)
I(1)-O(2)
I(1)-O(3)
I(2)-O(4)
I(2)-O(5)
I(2)-O(6)
I(3)-O(7)
I(3)-O(8)
I(3)-O(9)
I(4)-O(10)
I(4)-O(11)
I(4)-O(12)
I(5)-O(13)
I(5)-O(14)
I(5)-O(15)
V(1)-O(2)
V(1)-O(4)
V(1)-O(8)
V(1)-O(13)
V(1)-O(16)
V(1)-O(17)
I(1)-O(3)
I(1)-O(2)
I(1)-O(3)
Ti(1)-O(2) × 6
I(1)-O(3)
I(2)-O(4)
I(2)-O(4)
I(2)-O(5)
I(2)-O(5)
I(2)-O(6)
I(2)-O(6)
I(3)-O(7)
Mo(1)-O(1) × 2
Mo(1)-O(4) × 2
Mo(1)-O(7) × 2
I(3)-O(8)
I(3)-O(9)
I(4)-O(10)
I(4)-O(11)
I(4)-O(12)
Mo(1)-O(2)
Mo(1)-O(4)
Mo(1)-O(7)
Mo(1)-O(10)
Mo(1)-O(13)
Mo(1)-O(14)
0
observations regarding the out-of-center distortion of the d
displacements and discuss these displacements with respect
to primary and secondary distortion concepts.
19
transition metal. First, the magnitude of the distortion scales
as Mo6 > V > W > Nb > Ta > Ti , similar to
+
5+
6+
5+
5+
4+
20
the electronegativity of these cations. Second, corner (C
and edge (C
observed for Ti and V , whereas edge and face (C
4
)
Experimental Section
2
) type displacements are most commonly
Reagents. K
Aesar, 98+%), La
Aldrich, 98+%), MoO
2
CO
3
(Alfa Aesar, 99%), Ba(OH)
(99.9%), TiO (Aldrich, 99.9+%), V
(Aldrich, 99+%), and HIO (Aldrich,
9.5+%) were used as received.
2
2
‚8H O (Alfa
4+
5+
3
)
2
O
3
2
2 5
O
distortions are preferred for Mo6 and W . All three types
+
6+
(
9
3
3
5
+
of distortions, edge, face, and corner, are found with Nb
5
+
0
and Ta . Third, for the d transition metal to undergo an
out-of-center distortion, at least one of the oxide ligands
needs to be terminal or bonded to another d transition metal.
-
3
Syntheses. For BaTi(IO
OH) ‚8H
10-2 mol) of HIO
)
3 6
, 0.500 g (1.58 × 10 mol) of Ba-
-3
(
2
2
O, 0.200 g (2.50 × 10 mol) of TiO
2
, and 5.000 g (2.84
0
×
3
were combined with 10 mL of H
2
O. For
0
In other words, when all six oxide ligands of the d transition
LaTiO(IO ) , 0.300 g (9.21 × 10-4 mol) of La O , 0.200 g (2.50
3
5
2
3
-
3
-2
metal are further bonded to a lone pair cation, the transition
metal is undistorted. We rationalized this by noting that the
lone pair cation is in a “predistorted” coordination environ-
ment. Thus, any additional distortion would be unfavorable.
We report in this paper the synthesis, structure, and
× 10 mol) of TiO , and 5.000 g (2.84 × 10 mol) of HIO3
2
were combined with 10 mL of H
2
O. For Ba
‚8H
2
VO
2
(IO
3
)
4
‚(IO
3
), 0.500
-3
-3
g (1.58 × 10 mol) of Ba(OH)
of V
, and 5.000 g (2.84 × 10 mol) of HIO
with 10 mL of H O. For K MoO (IO
, 0.300 g (2.17 × 10 mol)
of K CO , and 5.000 g (2.84
, 0.300 g (2.08 × 10 mol) of MoO
10- mol) of HIO
were combined with 10 mL of H O. For
BaMoO (IO ‚H
O, 0.500 g (1.58 × 10 mol) of Ba(OH)
.500 g (3.47 × 10 mol) of MoO
mol) of HIO were combined with 10 mL of H
2
2
O, 0.200 g (1.10 × 10 mol)
-
2
O
2 5
3
were combined
-3
2
2
2
3 4
)
-
3
0
2
3
3
characterization of five new d transition metal iodates, BaTi-
2
×
3
2
3 6 3 5 2 2 3 4
(IO ) , LaTiO(IO ) , Ba VO (IO ) ‚(IO
3 2 2 3 4
), K MoO (IO ) , and
O. We also examine the various cationic
-3
2
)
3 4
2
2
‚8H
2
O,
BaMoO
2
(IO ‚H
3
)
4
2
-
3
-2
0
3
, and 5.000 g (2.84 × 10
3
2
O. The respective
(
(
19) Halasyamani, P. S. Chem. Mater. 2004, 16, 3586.
20) Eng, H. W.; Barnes, P. W.; Auer, B. M.; Woodward, P. M. J. Solid
State Chem. 2003, 175, 94.
solutions were placed in 23-mL Teflon-lined autoclaves and
subsequently sealed. The autoclaves were gradually heated to 230
2264 Inorganic Chemistry, Vol. 44, No. 7, 2005

0
New d Transition Metal Iodates
Figure 1. Ball-and-stick representation of BaTi(IO3)6 in the ab-plane. The Ba2+ cations have been removed for clarity.
°
C, held for 4 d, and cooled slowly to room temperature at a rate
-
1
of 6 °C h . The mother liquor was decanted from the products.
The products were recovered by filtration and washed with water
and ethanol. For Ba
were found in 69% yield based on V
IO , BaMoO (IO ‚H O, and K MoO
the only product from the reaction, were recovered in 79%, 81%,
8%, and 76% yields, respectively, based on the corresponding d0
2
VO
2 3
(IO )
4
‚(IO
3
), pale yellow plates crystals
. For BaTi(IO , LaTiO-
(IO , colorless crystals,
2
O
5
3 6
)
(
3
)
5
2
3
)
4
2
2
2
3 4
)
7
transition metal oxide.
Single-Crystal X-ray Diffraction. For BaTi(IO
3
)
6
a colorless
a colorless block
‚(IO ) a light yellow
(IO ‚H O a colorless
MoO (IO a colorless
3
cube (0.06 × 0.08 × 0.10 mm ), for LaTiO(IO
3 5
)
3
(
0.12 × 0.16 × 0.22 mm ), for Ba
2 2 3
VO (IO )
4
3
3
plate (0.02 × 0.06 × 0.12 mm ), for BaMoO
2
3
)
4
2
3
block (0.12 × 0.20 × 0.22 mm ), and for K
2
2
3 4
)
3
block (0.16 × 0.22 × 0.46 mm ) were used for single-crystal data
analyses. Data were collected using a Siemens SMART diffracto-
meter equipped with a 1K CCD area detector using graphite
monochromated Mo KR radiation. A hemisphere of data was
collected using a narrow-frame method with scan widths of 0.30°
in ω, and an exposure time of 25 s per frame. The first 50 frames
were remeasured at the end of the data collection to monitor
instrument and crystal stability. The maximum correction applied
to the intensities was <1%. The data were integrated using the
Siemens SAINT program,21 with the intensities corrected for
Lorentz, polarization, air absorption, and absorption attributable to
the variation in the path length through the detector faceplate.
ψ-scans were used for the absorption correction on the hemisphere
of data. The data were solved and refined using SHELXS-97 and
SHELXL-97, respectively.2 All of the atoms were refined with
anisotropic thermal parameters and converged for I > 2σ(I). All
calculations were performed using the WinGX-98 crystallographic
software package.24 During the course of the refinement for BaTi-
2
-
Figure 2. Ball-and-stick representation of the [Ti(IO3)6] anionic unit in
4+
5+
BaTi(IO3)6. All six oxide ligands linked to Ti are also bonded to an I
cation. Thus, the Ti4 cation is in an undistorted environment with six equal
+
Ti-O bonds.
(
3 6
IO ) , we determined that fractional occupancy must occur in the
barium atoms to retain charge balance. Fractional occupancy of
.500(3) was refined for Ba . Relevant crystallographic data and
2+
0
selected bond distances are given in Tables 1 and 2, respectively.
Powder X-ray Diffraction. Powder X-ray diffraction was used
to confirm the phase purity of each sample. The X-ray powder
diffraction data were collected on a Scintag XDS2000 diffractometer
at room temperature (Cu KR radiation, θ-θ mode, flat plate
geometry) equipped with Peltier germanium solid-state detector in
the 2θ range 5-60° with a step size of 0.02°, and a step time of 1
s.
2,23
(
21) SAINT, Version 4.05: Program for Area Detector Absorption Cor-
rection; Siemens Analytical X-ray Instruments: Madison, WI, 1995.
22) Sheldrick, G. M. SHELXS-97-A program for automatic solution of
crystal structures; University of Goettingen: Goettingen, Germany,
(
Infrared and Raman Spectroscopy. Infrared spectra were
recorded on a Matteson FTIR 5000 spectrometer in the 400-4000
cm range, with the sample pressed between two KBr pellets.
1997.
(
23) Sheldrick, G. M. SHELXL-97-A program for crystal structure refine-
ment; University of Goettingen: Goettingen, Germany, 1997.
24) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837.
-
1
(
Raman spectra were recorded at room temperature on a Digilab
Inorganic Chemistry, Vol. 44, No. 7, 2005 2265

Ok and Halasyamani
Figure 3. Ball-and-stick representation of LaTiO(IO3)5 in the ab-plane. The dashed lines indicate long I-O interactions giving the structure a pseudo-
one-dimensional topology.
Poly(tetrafluoroethylene) was used as a reference material. Reflec-
tance spectra were converted to absorbance with the Kubelka-
Munk values.25
Thermogravimetric Analysis. Thermogravimetric analyses were
carried out on a TGA 2950 thermogravimetric analyzer (TA
instruments). The sample was contained within a platinum crucible
-
1
and heated in air at a rate of 10 °C min to 800 °C.
Results
Structures. BaTi(IO
consists of a TiO octahedron linked to six IO
that are separated by Ba cations (see Figure 1). In
3 6
)
. The zero-dimensional BaTi(IO
3 6
)
6
3
polyhedra
2
+
2
-
connectivity terms, the structure may be written as {[TiO6/2
]
0
2-
2+
6
[IO1/2O2/1] } , with charge balance maintained by the Ba
4
+
3
-
cations. Each Ti cation is bonded to six oxygen atoms in
Figure 4. Ball-and-stick representation of the [TiO(IO3)5] anionic unit
4+
in LaTiO(IO3)5. Note that the Ti undergoes an out-of-center displacement
toward an apical oxide ligand, along the local C4 direction. The arrow
indicates the approximate direction of the local dipole moment in the TiO6
octahedron.
an octahedral environment with a unique Ti-O bond distance
4+
of 1.939(5) Å. All six oxygen atoms linked to the Ti cation
5
+
5+
are further bonded to an I cation. The I cations are
bonded to three oxygen atoms in a distorted trigonal
pyramidal environment with I-O bond distances ranging
from 1.791(5) to 1.858(5) Å (see Figure 2). The bond
distances are consistent with similar compounds previously
FTS 7000 spectrometer equipped with a germanium detector with
the powder sample placed in separate capillary tubes. Excitation
was provided by a Nd:YAG laser at a wavelength of 1064 nm,
and the output laser power was 500 mW. The spectral resolution
2
6-31
32,33
reported.
Bond valence calculations
resulted in values
-
1
was ∼4 cm , and 100 scans were collected for each sample.
UV-Vis Diffuse Reflectance Spectroscopy. UV-vis diffuse
reflectance data for all of the reported crystalline samples were
collected with a Varian Cary 500 scan UV-vis-NIR spectropho-
tometer over the spectral range 200-1500 nm at room temperature.
2+ 5+
4+
of 2.22, 4.95, and 4.29 for Ba , I , and Ti , respectively.
(
25) Kubelka, P.; Munk, F. Z. Tech. Phys. 1931, 12, 593.
(26) Schellhaas, F.; Hartl, H.; Frydrych, R. Acta Crystallogr. 1972, B28,
2834.
(27) Alcock, N. W. Acta Crystallogr. 1972, B28, 2783.
2266 Inorganic Chemistry, Vol. 44, No. 7, 2005

0
New d Transition Metal Iodates
Figure 5. Ball-and-stick representation of Ba2VO2(IO3)4‚(IO3) in the bc-plane. Note the “free” [IO3]- anionic groups between the molecular units.
0
LaTiO(IO
3
)
5
. This d transition metal iodate exhibits a
dashed line in Figure 3. This long contact effectively links
the TiO octahedra, through this “IO ” group, and gives
LaTiO(IO a pseudo-one-dimensional topology. Bond
pseudo-one-dimensional structure consisting of a TiO
octahedron linked to five IO polyhedra that are separated
by La cations (see Figure 3). In connectivity terms, the
structure may be written as {[TiO5/2
with charge balance maintained by the La cation. Each
Ti is bonded to six oxygen atoms in an octahedral
environment with one “short” (1.695(5) Å), four “normal”
1.970(5)-2.042(5) Å), and one “long” bond (2.117(5) Å).
6
6
4
3
3 5
)
3
+
32,33
3+
valence calculations
5.01-5.48 for I , and 4.20 for Ti .
resulted in values of 3.14 for La ,
3-
0
3-
5+
4+
O
1/1
]
5[IO1/2
O
2/1] } ,
3
+
Ba
IO ) also exhibits a zero-dimensional structure that consists
of a VO octahedron linked to four IO groups (see Figure
). In connectivity terms, the structure maybe written as
2 2 3 4 3 3 6 2 2 3 4
VO (IO ) ‚(IO ). Similar to BaTi(IO ) , Ba VO (IO ) ‚
4
+
(
3
6
3
(
5
5
+
Five of the six oxygen atoms are further bonded to an I
3-
0
- 4-
{[VO2/1
O
4/2
]
4[IO2/1O1/2] ‚[IO3/1] } , with charge balance
cation, whereas the sixth, the “short” Ti-O bond, remains
terminal”. The Ti4+ cation displaces toward the terminal
oxygen atom, thereby undergoing an out-of-center distortion
toward a corner of its oxide octahedron, that is, a C
2+
retained by two Ba cations. Unlike the other zero-
“
dimensional compounds reported in this paper, Ba
2
VO
2
-
-
(IO
3
)
4
‚(IO
3
) has a completely unbound IO
3
anion, that is,
IO3/1] , that interacts with the Ba cations. Each V5+ is
-
2+
4
[
distortion (see Figure 4). We will be discussing all of the
various cationic distortions later in the paper. The I5+ cations
are linked to three oxygen atoms in a distorted trigonal
pyramidal environment with I-O bond distances ranging
from 1.794(5) to 1.878(5) Å (see Figure 4). There is one
long I-O contact of 2.197(5) Å that has been drawn as a
bonded to six oxygen atoms in an octahedral environment,
with two “short” V-O bonds of 1.639(7) and 1.646(7) Å,
two “normal” bonds of 1.975(6) Å × 2, and two “long”
bonds of 2.164(7) and 2.245(7) Å (see Figure 6). Four of
5+
the six oxygen atoms are further bonded to an I cation,
whereas the remaining two, the “short” V-O bonds, are
5
+
terminal. The V undergoes an out-of-center distortion, in
(
28) Coquet, E.; Crettez, J. M.; Pannetier, J.; Bouillot, J.; Damien, J. C.
the direction of the terminal oxygen atoms, toward an edge
Acta Crystallogr. 1983, B39, 408.
of its octahedron, that is, a C
2
distortion (see Figure 6). The
(
(
(
(
(
29) Lucas, B. W. Acta Crystallogr. 1984, C40, 1989.
5
+
30) Svensson, C.; Stahl, K. J. Solid State Chem. 1988, 77, 112.
31) Stahl, K.; Szafranski, M. Acta Chem. Scand. 1992, 46, 1146.
32) Brown, I. D.; Altermatt, D. Acta Crystallogr. 1985, B41, 244.
33) Brese, N. E.; O’Keeffe, M. Acta Crystallogr. 1991, B47, 192.
I
cations are linked to three oxygen atoms in a distorted
trigonal pyramidal environment with I-O bond distances
ranging from 1.784(7) to 1.866(6) Å. Bond valence calcula-
Inorganic Chemistry, Vol. 44, No. 7, 2005 2267

Ok and Halasyamani
3
-
Figure 6. Ball-and-stick representation of the [VO2(IO3)4] anionic unit
5
+
in Ba2VO2(IO3)4‚(IO3). Note that the V undergoes an out-of-center
displacement toward two equatorial oxide ligands, along the local C2
direction. The arrow indicates the direction of the local dipole moment in
the VO6 octahedron.
2-
Figure 8. Ball-and-stick representation of the [MoO2(IO3)4] anionic unit
in K2MoO2(IO3)4. Note that the Mo6 undergoes an out-of-center displace-
ment toward two equatorial oxide ligands, along the local C2 direction. The
arrow indicates the direction of the local dipole moment in the MoO6
octahedron.
+
+
by K cations. In connectivity terms, the structure may be
2
-
0 2-
written as {[MoO2/1
4/2
O ]
4[IO2/1
O
1/2] } , with charge
+
6+
balance retained by two K cations. Each Mo cation is
bonded to six oxygen atoms in an octahedral environment
with two “short” Mo-O bonds of 1.710(4) Å × 2, two
“
normal” bonds of 1.955(4) Å × 2, and two “long” bonds
5+
2 2
of 2.238(4) Å × 2. Similar to the V cations in Ba
IO ‚(IO ), four of the six oxygen atoms are further bonded
to an I cation, whereas the remaining two oxygen atoms
VO -
(
)
3 4
3
5
+
6+
are terminal. The Mo undergoes an out-of-center distortion,
in the direction of the terminal oxygen atoms, toward the
edge of its octahedron, that is, a C
2
distortion (see Figure
5
+
8
). The I cations are linked to three oxygen atoms in a
distorted trigonal pyramidal environment with I-O bond
distances ranging from 1.784(4) to 1.912(4) Å. Bond valence
3
2,33
+
calculations
5
resulted in values of 1.18 for K , 5.05 and
5
+
6+
.10 for I , and 5.98 for Mo .
BaMoO
cally very similar to K
exhibits a zero-dimensional structure consisting of a MoO
octahedron linked to four IO groups that are separated by
O molecules and Ba cations (see Figure 9). In con-
2 3 4 2
(IO ) ‚H O. This mixed-metal iodate is topologi-
2
MoO (IO . BaMoO (IO ‚H
2
3
)
4
2
3
)
4
2
O
6
3
2
+
H
2
2
-
2/1
nectivity terms, the structure may be written as {[MoO4/2O ]
0
2-
2+
4
[IO2/1
O
1/ 2] } , with charge balance retained by the Ba
Figure 7. Ball-and-stick representation of K2MoO2(IO3)4 in the ac-plane.
6+
cation. Each Mo cation is bonded to six oxygen atoms in
an octahedral environment with two “short” Mo-O bonds
of 1.699(4) and 1.709(4) Å, two “normal” bonds of 1.962-
(4) and 2.006(4) Å, and two “long” bonds of 2.191(4) and
+
2-
The K cations separate the [MoO2(IO3)4] anionic units.
tions32,33 resulted in values of 2.07 and 2.08 for Ba , 4.89-
2+
5
+
5+
5
.19 for I , and 5.02 for V .
MoO (IO . A zero-dimensional structure is also
exhibited by K MoO (IO , where a MoO octahedron is
linked to four IO polyhedra (see Figure 7), that are separated
K
2
2
3
)
4
2.196(4) Å. The short Mo-O bonds are terminal, whereas
+
2
2
)
3 4
6
the remaining four link to the IO
3
polyhedra. Again, the Mo6
3
cation displaces in the direction of the terminal oxygen atoms,
2268 Inorganic Chemistry, Vol. 44, No. 7, 2005

0
New d Transition Metal Iodates
2
-
Figure 10. Ball-and-stick representation of the [MoO2(IO3)4] anionic
unit in BaMoO2(IO3)4‚H2O. Note that the Mo6 undergoes an out-of-center
displacement toward two equatorial oxide ligands, along the local C2
direction. The arrow indicates the direction of the local dipole moment in
the MoO6 octahedron.
+
Figure 9. Ball-and-stick representation of BaMoO2(IO3)4‚H2O in the ac-
plane. The Ba cations and H2O molecules separate the [MoO2(IO3)4]2-
2+
anionic units.
UV-Vis Diffuse Reflectance Spectroscopy. The UV-
vis diffuse reflectance spectra for all of the reported iodates
have been deposited in the Supporting Information. All of
toward the edge of its octahedron, that is, a C
(
atoms in a distorted trigonal pyramidal environment with
2
distortion
see Figure 10). The I5+ cations are linked to three oxygen
the compounds are white with the exception of Ba
2 2 3 4
VO (IO ) -
I-O bond distances ranging from 1.779(4) to 1.897(4) Å.
(
IO ), which is light yellow. These spectra show that the
3
3
2,33
Bond valence calculations
resulted in values of 1.78 for
iodate compounds are transparent to approximately 3.2-3.8
eV. Absorption (K/S) data were calculated from the following
Kubelka-Munk function:
2+
5+
6+
Ba , 4.85-5.07 for I , and 6.01 for Mo .
Infrared and Raman Spectroscopy. The infrared and
Raman spectra of BaTi(IO
IO ), K MoO (IO , and BaMoO
O, V-O, and Mo-O vibrations in the regions ca. 700, 700-
3
)
6
, LaTiO(IO
3
)
5
, Ba
2 2 3 4
VO (IO ) ‚
(
3
2
2
)
3 4
2
(IO
3
)
4
‚H O reveal Ti-
2
2
(
1 - R)
K
S
F(R) )
)
2
R
-
1
9
8
00, and 700-940 cm , respectively. The stretches 620-
-1
30 and 360-560 cm can be attributed to I-O vibrations.
with R representing the reflectance, K the absorption, and S
the scattering. In a K/S versus E (eV) plot, extrapolating the
linear part of the rising curve to zero provides the onset of
absorption at 3.3, 3.4, 3.2, 3.6, and 3.8 eV for BaTi(IO ) ,
The infrared and Raman vibrations and assignments are listed
in Table 3. The assignments are consistent with those
previously reported.3
4-40
3
6
LaTiO(IO , Ba
3
)
5
2
VO
2
(IO
3
)
4
‚(IO
3
), BaMoO
2
(IO
3
)
4
2
‚H O, and
(
(
(
(
(
(
(
34) Sykora, R. E.; Ok, K. M.; Halasyamani, P. S.; Wells, D. M.; Albrecht-
K
2
MoO (IO ) , respectively. The overall band gap for each
2
3 4
Schmitt, T. E. Chem. Mater. 2002, 14, 2741.
35) Sykora, R. E.; Ok, K. M.; Halasyamani, P. S.; Albrecht-Schmitt, T.
E. J. Am. Chem. Soc. 2002, 124, 1951.
36) Shehee, T. C.; Sykora, R. E.; Ok, K. M.; Halasyamani, P. S.; Albrecht-
Schmitt, T. E. Inorg. Chem. 2003, 42, 457.
37) Maggard, P. A.; Kopf, A. L.; Stern, C. L.; Poeppelmeier, K. R.; Ok,
K. M.; Halasyamani, P. S. Inorg. Chem. 2002, 41, 4852.
38) Guarany, C. A.; Pelaio, L. H. Z.; Araujo, E. B.; Yukimitu, K.; Moraes,
J. C. S.; Eiras, J. A. J. Phys.: Condens. Matter 2003, 15, 4851.
39) Rasmussen, S. B.; Rasmussen, R. M.; Fehrmann, R.; Nielsen, K. Inorg.
Chem. 2003, 42, 7123.
material may be attributable to the degree of Ti (3d), V (3d),
and Mo (4d) orbitals as well as the distortions of crystal
structures arising from IO polyhedra. LaTiO(IO ) , however,
3 3 5
reveals a small shoulder near the main absorption band,
suggesting an indirect transition.
Thermogravimetric Analysis. All of the iodate com-
pounds reported in this paper are not stable at higher
temperatures. With each material, decompositions through
thermal disproportionation occurred between 400 and 460
40) Rasmussen, S. B.; Boghosian, S.; Nielsen, K.; Eriksen, K. M.;
Fehrmann, R. Inorg. Chem. 2004, 43, 3697.
Inorganic Chemistry, Vol. 44, No. 7, 2005 2269

Ok and Halasyamani
Table 3. Infrared and Raman Vibrations (cm-1) for BaTi(IO3)6, LaTiO(IO3)5, Ba2VO2(IO3)4·(IO3), K2MoO2(IO3)4, and BaMoO2(IO3)4‚H2O
BaTi(IO3)6 LaTiO(IO3)5 Ba2VO2(IO3)4‚(IO3) K2MoO2(IO3)4 BaMoO2(IO3)4‚H2O
Ti-O I-O
Ti-O
I-O
V-O
I-O
Mo-O
I-O
Mo-O
I-O
O-H
IR (cm-1)
827
6
5
5
98
88
03
821
813
779
700
568
493
836
819
808
794
771
748
642
451
424
1166
901
881
869
794
709
682
489
925
885
715
638
511
495
819
769
744
431
412
937
914
892
561
499
827
815
777
763
740
713
644
474
420
3563
3502
1604
815
771
761
742
455
433
418
7
6
4
4
4
4
69
49
57
39
24
16
Raman (cm-1)
7
6
5
17
71
13
821
806
779
713
690
813
806
759
740
624
482
462
898
879
790
713
675
486
821
775
744
447
428
416
921
875
705
825
806
763
748
663
505
420
401
389
933
910
883
725
698
821
802
779
763
740
655
505
482
424
7
6
4
3
52
40
08
66
4
3
12
89
412
0
Table 4. Direction and Magnitude of the d Transition Metal
Intra-Octahedral Distortion in BaTi(IO3)6, LaTiO(IO3)5,
Ba VO (IO ) ·(IO ), K MoO (IO ) , and BaMoO (IO ) ‚H O
°
C. For BaTi(IO
3
)
6
2 2
, 2 equiv of I and 5 equiv of O are lost
at approximately 420 °C: calc.(exp.) 54.07%(54.26%). The
remainder of the I and O are lost at approximately 530
C: calc.(exp.) 58.87%(58.53%). For BaTi(IO
remains above 800 °C. With LaTiO(IO , 2 equiv of O
2
2
3 4
3
2
2
3 4
2
3 4
2
2
2
compound
direction - cation
magnitude
°
3
)
6
, BaTiO
3
BaTi(IO3)6
LaTiO(IO3)5
Ba2VO2(IO3)4‚(IO3)
K2MoO2(IO3)4
no distortion - Ti4
+
0.00
0.55
1.16
1.09
1.06
3
)
5
2
is
4+
C4 - Ti
C2 - V5
+
lost at approximately 400 °C, calc.(exp.) 5.94%(5.75%).
Next, 1 equiv of I and another 1.5 equiv of O are lost at
around 570 °C, calc.(exp.) 29.78% (29.68%). Finally, the
remainder of I and O are lost, leaving a mixture of La
and TiO at around 800 °C: calc.(exp.) 65.88%(66.02%).
Ba VO (IO ‚(IO ) loses 1 mol of I and 2.75 mol of O at
around 460 °C: calc.(exp.) 27.74%(28.13%). Next, 0.5 mol
of I and 1.75 mol of O are subsequently lost at ap-
proximately 540 °C: calc.(exp.) 20.54%(20.24%). The
remainder of I and O are lost at around 800 °C, leaving a
mixture of BaO and V : calc.(exp.) 43.79%(43.84%).
With K MoO (IO , single step decomposition occurs at
around 400 °C, indicating the loss of 2 mol of I and 5 mol
of O : calc.(exp.) 73.71%(73.64%). BaMoO (IO ‚H
C2 - Mo6
C2 - Mo6
+
+
2
2
BaMoO2(IO3)4‚H2O
2
2
2 3
O
3
the oxide octahedra and the IO polyhedra. In oxide materials
2
0
that contain d transition metals and lone pair cations, the
direction and magnitude of the out-of-center displacement
2
2
3
)
4
3
2
2
0
of the d transition metal depend on the coordination of the
2
2
0
19
oxide ligands as well as the particular d transition metal.
In materials where all six oxide ligands are further bonded
2
2
0
to a lone pair cation, we noted that the d transition metal is
2 5
O
undistorted, effectively “trapped” in the center of its coor-
dination polyhedra. In other words, the secondary distortion
2
2
3 4
)
2
0
overrides the primary distortion of the d transition metal.
2
2
)
3 4
2
O
This is precisely the situation that occurs in BaTi(IO
3
)
6
(see
shows a weight loss at 330 °C that is attributed to the loss
of the occluded water molecules from the materials: calc.-
Figure 2). In BaTi(IO ) , all six oxide ligands surrounding
3 6
4+
5+
4+
Ti are further bonded to an I cation. If the Ti cation
were to distort toward one or more of the oxide ligands, a
(
exp.) 1.83%(1.93%). Next, 2 equiv of I
are lost at approximately 410 °C, leaving a mixture of BaO
and MoO at 800 °C: calc.(exp.) 69.19%(69.89%). The TGA
2 2
and 5 equiv of O
compensating distortion within an IO
3
group would be
3
required. Because the IO polyhedra are already “predis-
3
curves for all five materials have been deposited in the
Supporting Information.
torted”, attributable to the lone pair, any additional distortion
4+
3 5
would be unfavorable. Thus, the Ti in BaTi(IO ) remains
in the center of its oxide octahedron with six equal Ti-O
bonds of 1.939(5) Å (see Figure 2).
Discussion
0
In all of the reported materials, the d transition metal is
in an octahedral coordination environment bonded to six
oxygen atoms. The oxide ligands are either terminal or
bonded to an I cation. As previously discussed, primary
and secondary distortion concepts can be used to better
understand these materials. For the reported materials, the
primary distortion is the electronic (SOJT) distortion that
occurs for both the d transition metal and the I cation,
whereas the secondary distortion is the interaction between
With the other materials, LaTiO(IO
3
)
5
, BaVO
O, the d transition
2
(IO
3
)
4
‚(IO
3
),
0
K
2
MoO (IO , and BaMoO (IO )‚H
2
3
)
4
2
3
2
4
+
5+
6+
metal, Ti , V , or Mo , respectively, is displaced from
the center of its oxide octahedron. The direction and
magnitude of these distortions are consistent with those
5
+
19
observed earlier for this class of compounds (see Table 4).
4
+
With Ti , in LaTiO(IO
3
)
5
, the cation is displaced toward
direction
-Ti type displacement is the most
0
5+
an apical, terminal, oxygen atom, along the local C
(see Figure 4). This C
4
4
+
4
2270 Inorganic Chemistry, Vol. 44, No. 7, 2005

0
New d Transition Metal Iodates
4
+
-Ti4+ distortion
common for Ti . The magnitude of this C
is 0.55 (using the methodology outlined earlier), which is
4
Note Added after ASAP: After this paper had been
published on the Web (March 8, 2005), it was brought to
19
4
+
larger than the average distortion observed for Ti . Very
3 4
similar types of distortions are observed in BaVO (IO ) ‚
our attention that the synthesis and structure of K
was previously published by Sykora et al. (J. Solid State
Chem. 2002, 166, 442). In addition, BaTi(IO is structurally
2 2 3 4
MoO (IO )
2
5
+
(IO
3
6
), K
2
MoO
2
(IO
3
)
4
, and BaMoO
2
(IO
3
)‚H
2
O for V and
3 6
)
+
Mo , respectively. In all three materials, the distortions are
toward the two terminal oxide ligands, along the local C
direction (see Figures 6, 8, and 10). These C
Mo distortions are commonly observed for both cations.
The magnitudes of the distortions are very large, >1.0,
consistent with our previous observations.19
similar to compounds reported by Schellhaas et al. (Acta
Crystallogr. 1972, B28, 2834) and Shehee et al. (J. Alloys
Compd. 2005, 388, 225). We regret the omissions. The Web
version published on March 23, 2005, and the print version
of the article are correct.
2
-V5 and C
+
2
2
-
6
+
Supporting Information Available: X-ray crystallographic files
for BaTi(IO
and BaMoO
3
)
6
, LaTiO(IO
3
)
5
, Ba
2
VO
2
(IO
3
)
4
‚(IO
3 2 2 3 4
), K MoO (IO ) ,
Acknowledgment. We thank the Robert A. Welch
Foundation for support. This work was also supported by
the NSF-Career Program through DMR-0092054. P.S.H. is
a Beckman Young Investigator. We also acknowledge Jason
Locklin and Prof. Rigoberto Advincula for assistance in
obtaining the Raman spectra.
2
(IO ‚H O in CIF format, ORTEP diagrams, calcu-
3
)
4
2
lated and observed X-ray diffraction patterns, thermogravimetric
analysis diagrams, UV-vis spectra, a bond valence table, and IR
spectra for all of the compounds. This material is available free of
charge via the Internet at http://pubs.acs.org.
IC048428C
Inorganic Chemistry, Vol. 44, No. 7, 2005 2271