Synthesis of zigzag-chain and cyclic-octanuclear calcium complexes and hexanuclear bulky aryl-phosphate sodium complexes with ortho-amide groups: Structural transformation involving a network of inter- and intramolecular hydrogen bonds

Article abstract of DOI:10.1021/ja011457r

Three new polynuclear Ca(II)- and Na(I) phosphate complexes with two strategically oriented bulky amide groups, 2,6-(PhCONH)₂C₆ H₃OPO₃H₂, were synthesized, including one with a zigzag-chain, [Ca^I

Full text of DOI:10.1021/ja011457r

Published on Web 01/17/2002
Synthesis of Zigzag-Chain and Cyclic-Octanuclear Calcium
Complexes and Hexanuclear Bulky Aryl-Phosphate Sodium
Complexes with Ortho-Amide Groups: Structural
Transformation Involving a Network of Inter- and
Intramolecular Hydrogen Bonds
Akira Onoda, Yusuke Yamada, Taka-aki Okamura, Mototsugu Doi,
Hitoshi Yamamoto, and Norikazu Ueyama*
Contribution from the Department of Macromolecular Science, Graduate School of Science,
Osaka UniVersity, Toyonaka, Osaka 560-0043 Japan
Received June 14, 2001
Abstract: Three new polynuclear Ca(II)- and Na(I) phosphate complexes with two strategically oriented
bulky amide groups, 2,6-(PhCONH)2C6H3OPO3H2, were synthesized, including one with a zigzag-chain,
[CaII{O3POC6H3-2,6-(NHCOPh)2}(H2O)4(EtOH)]n, a cyclic-octanuclear form, [CaII8{O3POC6H3-2,6-(NHCOPh)2}8-
(OdCHNMe2)8(H2O)12], and a hexanuclear complex, (NHEt3)[Na3{O3POC6H3-2,6-(NHCOPh)2}2(H2O)-
(MeOH)7]. X-ray crystallography revealed that all have an unsymmetric ligand position due to the bulky
amide groups. A dynamic transformation of the Ca(II) zigzag-chain structure to the cyclic-octanuclear
complex was induced by changing coordination of DMF molecules, which caused a reorganization of the
intermolecular/intramolecular hydrogen bond network.
Introduction
bond networks play an important role for developing a variety
of metal-phosphate complexes.21-30 Similar structures have
The structural polynuclear phosphate complexes with various
metal ions and hydrogen-bond donor ligands provide fascinating
insight for the design of solid-state materials. Ca(II) phosphate
complexes are of special interest for their relevance to biological
issues, and their structure in particular may yield clues for
understanding the biomineralization of Ca(II) phosphate materi-
als, such as bone and teeth.1-6 It has been reported that synthetic
metal-phosphate complexes with small ligands have open-
framework structures,7-20 in which intermolecular hydrogen-
important applications for ion exchange and catalysis.
We have previously synthesized novel mononuclear Ca(II)
phosphate complexes with an extremely bulky amide ligand,31
whose mononuclear structure enabled us to investigate the role
of intramolecular NH‚‚‚O hydrogen bonds to the phosphate
groups, because the bulky ligand interrupts the formation of
intermolecular hydrogen-bond interactions. The bulky triphen-
ylacylamino groups lead to the formation of a mononuclear
Ca(II) core in both the phosphate monoanion and dianion states.
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9
1052 VOL. 124, NO. 6, 2002 J. AM. CHEM. SOC.
10.1021/ja011457r CCC: $22.00 © 2002 American Chemical Society

Synthesis of Ca(II)- and Na(I) Phosphate Complexes
A R T I C L E S
Scheme 1. Novel Aryl Dihydrogen Phosphate Ligand with Bulky
Amide Substituents in Ortho Positions
1 M NaOH aqueous methanol (1:1). The solution was neutralized with
concentrated aqueous HCl and concentrated in vacuo. The residue was
extracted with portions of 100 mL of ether, and the separated organic
layer was washed with saturated aqueous NaCl solution, dried over
Na2SO4, and concentrated in vacuo to give a pale-yellow powder. Yield,
1
80%. H NMR (CDCl3): δ 9.94 (s, 2H, OH), 8.54 (s, 2H, NH), 7.95
(d (J ) 7.14 Hz), 4H, m-PhH), 7.63 (d (J ) 8.06 Hz), 2H, m-ArH),
7.60 (t (J ) 7.14 Hz), 2H, p-PhH), 7.53(d (J ) 7.55 Hz), 4H, m-PhH),
6.98 (t (J ) 8.06 Hz), 1H, p-ArH). Anal. Calcd for C20H16N2O3: C,
72.28; H, 4.85; N, 8.43. Found: C, 72.10; H,4.79; N, 8.42.
2,6-(PhCONH)2C6H3OPO3H2 (1). To a suspension of 2,6-(Ph-
CONH)2C6H3OH (1.7 g, 5.2 mmol) in 60 mL of acetonitrile were added
orthophosphoric acid (1.2 g, 12 mmol), triethylamine (3.3 mL, 22
mmol), and trichloroacetonitrile (3.1 mL, 31 mmol) to give a
homogeneous green solution. This solution was stirred for 5 h at room
temperature and concentrated under reduced pressure. To the residue
was added 50 mL of water, and the aqueous phase was washed with
ether a few times to remove the unreacted phenol. The aqueous phase
was adjusted to pH 8 with 1 M NaOH aqueous solution and
concentrated in vacuo to remove triethylamine. The concentrated
solution was acidified with concentrated HCl. Colorless needles
precipitated in 1 week. Yield, 19%. 1H NMR (DMSO-d6): δ 10.13 (s,
2H, NH), 8.00 (d (J ) 8.25 Hz), 4H, m-PhH), 7.95 (d (J ) 8.06 Hz),
2H, m-ArH), 7.60 (t (J ) 7.14 Hz), 2H, p-PhH), 7.53(d (J ) 7.11 Hz),
4H, m-PhH), 7.21 (t (J ) 8.06 Hz), 1H, p-ArH). MS (ESI) Calcd (found)
m/e: 2,6-(PhCONH)2C6H3OPO3H-, 411.3 (411.6). 31P NMR (DMSO-
d6): δ -1.13 ppm. 31P NMR (in the solid state): δ -6.6 ppm. Anal.
Calcd for C20H17N2O6P‚(H2O)0.5: C, 57.01; H, 4.31; N, 6.65. Found:
C, 56.77; H, 4.32; N, 6.53. pKa1 and pKa2 values: 4.3 and 7.1 in 5 mM
Triton X-100/10% aqueous micellar solution.
(NHEt3){2,6-(PhCONH)2C6H3OPO3H} (2a). To a suspension of
2,6-(PhCONH)2C6H3OH (550 mg, 1.7 mmol) in 30 mL of acetonitrile
were added orthophosphoric acid (380 g, 3.9 mmol), triethylamine (1.1
mL, 7.8 mmol), and trichloroacetonitrile (1.0 mL, 10 mmol) to give a
homogeneous green solution. This solution was stirred for 5 h at room
temperature. To the residue was added 10 mL of water, and the aqueous
phase was washed with ether a few times to remove the unreacted
phenol. Acidification of the solution gave a white precipitate, which
was recrystallized from acetonitrile. Yield 46%. Anal. Calcd for
C26H32N3O6P1: C, 60.81; H, 6.28; N, 8.18. Found: C,60.81; H,6.23;
N,8.24.
The intramolecular NH‚‚‚O hydrogen bonds to the phosphate
groups, which are not formed in a phosphoric acid state, are
weak in a monoanion state and strong in a dianion state. The
NH‚‚‚O hydrogen bonds to the coordinating phosphate groups
prevent the Ca-O bond from dissociating. The correlation study
between the distance of a Ca-O bond and the angles of a Ca-
O-P among various Ca(II) phosphate complexes showed the
presence of the covalent bond character in the Ca-O bonds. In
fact the analysis for our mononuclear Ca(II) complex gives the
shortest Ca-O bond. The very bulky amide group seemed to
restrict the coordination of the phosphate groups to the Ca(II)
ion and the formation of intermolecular hydrogen-bond net-
works.
It is known that the various Ca(II) complexes with phosphate,
ROPO3, and phosphonate ligands, RPO3, such as Ca(O3POCH2-
CH2NH3), have a one-dimensional structure32-35 and the others,
such as Ca(O3PMe), have layered structures,36-39 whereas Na
phosphate complexes are reported to be polymeric as well.40-42
In this present work, we show our synthetic novel phosphate
ligands with bulky benzoylamino groups in ortho positions
(Scheme 1), zigzag-chain, cyclic-octanuclear Ca(II) and hexa-
nuclear Na(I) complexes forming intramolecular and intermo-
lecular hydrogen-bond networks. These phosphate complexes
give a unique unsymmetric ligand position to the metal ions.
We present a report of their isolation method and characteriza-
tion by X-ray studies and by NMR and IR spectra.
Experimental Section
Materials. All solvents were distilled over appropriate drying agents
and degassed prior to use. All starting reagents were of commercial
grade. 2,6-Dibenzoylaminophenyl dihydrogen phosphate was synthe-
sized by the reported methods.43
2,6-(PhCONH)2C6H3OH. A suspension of 970 mg (4.9 mmol) of
2,6-(NH2)C6H3OH‚2HCl was prepared in 130 mL of dichloromethane.
To the suspension, 3.6 mL (26 mmol) of triethylamine and 1.8 mL (19
mmol) of benzoyl chloride were added at 0 °C under Ar atmosphere.
After being stirred for a few hours, the solution was brought to room
temperature with additional stirring. After the addition of water, the
solution was concentrated in vacuo to give a white precipitate, which
was a benzoyl ester of the final product. The ester was hydrolyzed in
(NEt4){2,6-(PhCONH)2C6H3OPO3H} (2b). To a solution of 100
mg (0.24 mmol) of 2,6-(PhCONH)2C6H3OPO3H2 in 3 mL of methanol
was added 63 mg (0.24 mmol) of (NEt4)(OAc) in 3 mL of aqueous
methanol, and the solution was concentrated under reduced pressure.
The residue was recrystallized from acetonitrile-ether to give colorless
crystals. Yield, 71%. Anal. Calcd for C28H36N3O6P1: C, 62.10; H, 6.70;
N, 7.76. Found: C, 62.17; H, 6.67; N, 7.83.
[CaII{O3POC6H3-2,6-(NHCOPh)2}(H2O)4(EtOH)]n (3). To a solu-
tion of 1 (68 mg, 0.16 mmol) in 2 mL of MeOH was added an aqueous
solution of Ca(OAc)2‚H2O (28 mg, 0.16 mmol) in 1 mL of water. The
solution was concentrated in vacuo, and the residue was recrystallized
from ethanol to give colorless crystals. Yield, 25%. Anal. Calcd for
C20H15CaN2O6P1‚(H2O)4: C, 45.98; H, 4.44; N, 5.36. Found: C, 45.54;
H, 4.69; N, 5.19. This compound was confirmed by X-ray structure
determination.
[CaII8{O3POC6H3-2,6-(NHCOPh)2}8(OdCHNMe2)8(H2O)12] (4).
3 was recrystallized from DMF/ether to precipitate colorless crystals.
Anal. Calcd for C184H200Ca8N24O68P8‚(DMF)4(H2O)18: C, 47.06; H,
5.28; N, 7.84. Found: C, 47.07; H, 5.08; N, 7.79. This compound was
confirmed by X-ray structure determination.
(NHEt3)[Na3{O3POC6H3-2,6-(NHCOPh)2}2(H2O)(MeOH)7] (5).
(NHEt3){2,6-(PhCONH)2C6H3OPO3H} (752 mg, 1.46 mmol) was
dissolved in 5 mL of MeOH, and 1.5 equiv of aqueous NaOH solution
was added. The solution was concentrated, and the residue was
recrystallized from MeOH/ether. Yield 35%. Anal. Calcd for C46H45N5-
(32) Li, C.-T.; Caughlan, C. N. Acta Crystallogr. 1965, 19, 637-645.
(33) Bissinger, P.; Kumberger, O.; Schier, A. Chem. Ber. 1990, 124, 509-513.
(34) Sato, T. Acta Crystallogr. 1984, C40, 738-740.
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1988, C44, 796-799.
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9
J. AM. CHEM. SOC. VOL. 124, NO. 6, 2002 1053

A R T I C L E S
Onoda et al.
Table 1. Crystallographic Data for 2a, 2b, 3, 4 and 5
parameter
2a
2b
3
4‚(DMF)8(H O)11
5
2
empirical formula
formula weight
color
crystal system
lattice parameter
a, Å
C26H32O6N3P
513.53
colorless
triclinic
C28H36N3O6P
541.57
colorless
C22H29CaN2O11P
568.52
colorless
C208H278Ca8N32O87P8
5187.02
colorless
C53H76N5Na3O20P2
1234.1
colorless
orthorombic
monoclinic
tetragonal
triclinic
11.910(3)
14.612(3)
8.142(1)
100.79(2)
108.64(1)
78.99(2)
1305.6(5)
P1h (no. 2)
2
18.678(6)
31.752(11)
9.380(6)
90
90
90
5563(4)
Pbca (no. 61)
8
1.293
1.45
16.960(5)
8.257(7)
18.754(7)
90
101.95(3)
90
2569(2)
P21/n (no. 14)
4
1.470
3.68
29.8134(5)
29.8134(5)
16.9925(3)
90
90
90
15103.6(4)
P4/n (no. 85)
2
1.141
2.60
15.1649(13)
16.8922(16)
14.3956(10)
114.6090(10)
109.742(5)
71.321(2)
3085.4(4)
P1h (no. 2)
2
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
space group
Z
F
calc, g cm-1
1.306
1.50
296
1.328
1.67
173
µ (Mo KR), cm-1
temp (K)
296
296
296
scan type
2θmax, deg
no. of collected reflns
no. of unique reflens
no. of reflns used
ω-2θ
ω-2θ
ω-2θ
ω
ω
50.0
55.0
50.0
55.0
55.0
4844
4600
2170
5806
5132
5132
(all)
344
0.053
0.248
3662
3231
3231
(all)
338
0.052
0.181
17887
17290
17290
(all)
631
0.105
0.340
21113
13273
13267
(all)
749
0.072
0.211
(I > 2σ(I))
no. of variables
R1a
325
0.062 (Rc)
wR2b
0.067 (Rw
)
d
2
2
2
2
a R1 ) Σ||Fo| - |Fc||/Σ|Fo|. [I > 2σ(I)]. b wR2 ) [Σw(Fo - Fc )2/Σw(Fo )2]1/2
.
c R ) Σ||Fo| - |Fc||/Σ|Fo|. d Rw ) [Σw(|Fo| - |Fc|)2/Σw|Fo| ]1/2; w )
1/σ2(|Fo|).
Na3O15P2‚(H2O)5(MeOH): C, 48.63; H, 5.12; N, 6.03. Found: C, 48.74;
H, 5.20; N, 6.16. MS (ESI) Calcd (found) m/e: [Na3{2,6-(PhCONH)2-
C6H3OPO3}2 + 2 H+]+, 891.2 (891.6). 23Na NMR (DMSO-d6): δ 0.54
ppm. 23Na MAS NMR (in the solid state): δ -11.4 ppm.
The structures were solved by the direct method and expanded using
Fourier techniques using a teXsan crystallographic software45 and
SHELXL-97.46 Non-hydrogen atoms were refined anisotropically, but
the hydrogen atoms were refined isotropically in 2a, 2b, 3, and 5.
Solvent molecules for 4 were refined isotropically, and all H atoms
except water H atoms were located at the calculated positions.
Physical Measurement. 1H NMR spectra in solution were recorded
on a JEOL EX 400 spectrometer. 31P and 23Na NMR and spectra in
solution were recorded on a Varian Unity Plus 600 MHz spectrometer.
31P, 23Na NMR, and CRAMPS (combined rotation and multipulse
Results and Discussion
1
spectroscopy) H NMR spectra in the solid state were recorded on a
Crystal Structures. Figure 1 represents the molecular
structures of (NHEt3){2,6-(PhCONH)2C6H3OPO3H} (2a), and
(NEt4){2,6-(PhCONH)2C6H3OPO3H} (2b). The P-O distances
for 2a, 1.502 (P1-O11), 1.491 (P1-O12), 1.549 Å (P1-O13),
indicate that O13 is protonated to give a P-O(H) single bond,
and the anionic charge due to the other oxygen atom is
delocalized over the other two P-O bonds. The distance of N1-
O11 (3.002(6) Å), N2-O12 (2.744(6) Å) for 2a and that of
N1-O12 (2.739(7) Å), N2-O13 (3.227(7) Å) are in a range
of forming NH‚‚‚O hydrogen bonds. The short O-O distance
(2.531(5) Å for 2a 2.528(6) Å for 2b) between O13 and O11
of the neighboring ligand indicates the formation of the P-OH‚
‚‚O-P hydrogen bonds between the two ligands in the
phosphate monoanion state to construct the dimer unit structures.
The molecular structure of a phosphate dianion complex, [Ca-
{O3POC6H3-2,6-(NHCOPh)2(H2O)4(EtOH)]n (3), is shown in
Figure 2a, and the selected bond distances and bond angles for
3 are listed in Table 2. The Ca(II) center is a seven-coordinate
structure in a capped-octahedral geometry. Four oxygen atoms
of water molecules, O21, O22, O23, and O24, coordinate to
Ca(II), and O31 of the ethanol is in the capping position. The
bond lengths, Ca1-O11 and Ca1-O13, are 2.427(4) Å and
2.326(5) Å, respectively which are within the normal range.37
1
Chemmagnetics CMX-300. CRAMPS H NMR spectra in the solid
state were taken with a 4 mm φ pencil rotor cell using an MREV-8
pulse sequence.44 IR spectra in the solid state of KBr pellets were taken
on a Jasco FT/IR-8300 spectrometer. The pKa measurement was
performed on a Metrohm 716 DMS Titrino. The pKa value for 1 was
measured in a 10% DMF-90% aqueous micellar (Triton X-100
micelles) solution. Mass spectroscopic analysis was performed on a
PE-Sciex API-III plus and Finniganmat LCQ-MS instrument.
X-ray Crsytal Structure Determination. The following crystals
of (NHEt3){2,6-(PhCONH)2C6H3OPO3H} (2a), (NEt4){2,6-(PhCO-
NH)2C6H3OPO3H}} (2b), [CaII{O3POC6H3-2,6-(NHCOPh)2{H2O)4-
(EtOH)]n (3), [CaII8{O3POC6H3-2,6-(NHCOPh)2}8(OdCHNMe2)8-
(H2O)12] (4), and (NHEt3)[Na3{O3POC6H3-2,6-(NHCOPh)2}2(H2O)-
(MeOH)7] (5) were sealed in glass capillaries. The X-ray data for 2a,
2b, and 3 were collected at 23 °C on a Rigaku AFC5R and an AFC7R
diffractometer equipped with a rotating anode X-ray generator. The
radiation used was Mo KR monochromatized with graphite (0.71069
Å). No empirical absorption correction was applied. Unit cell dimen-
sions were refined by 20 reflections. These standard reflections were
monitored with every 150 reflections and did not show any significant
change. The X-ray data for 4 and 5 were collected in 4.0 and 5.0°
oscillations at 296 and 173 K on a Raxis RAPID, respectively. Sweeps
of data for 4 and 5 was done using ω oscillations from 130.0 to 190.0°
at φ ) 0.0° and ø ) 45.0°, and from 0.0 to 160.0° at φ ) 180.0° and
ø ) 45.0°. The basic crystallographic parameters for 2a, 2b, 3, 4, and
5 are listed in Table 1.
(45) teXsan: Crystal Structure Analysis Package; Molecular Structure Corpora-
tion, 1985 and 1999.
(46) Sheldrick, G. M.; SHELXL-97, Program for the Refinement of Crystal
ed.: University of Gottingen, Germany, 1997.
(44) Rhim, W.-K.; Elleman, D. D.; Vaughan, R. W. J. Chem. Phys. 1973, 59,
3740-3749.
9
1054 J. AM. CHEM. SOC. VOL. 124, NO. 6, 2002

Synthesis of Ca(II)- and Na(I) Phosphate Complexes
A R T I C L E S
Figure 1. Molecular structure of (a) (NHEt3){2,6-(PhCONH)2C6H3OPO3H}
(2a) and (b) (NEt4){2,6-(PhCONH)2C6H3OPO3H} (2b). A dashed line
indicates a hydrogen bonds.
Table 2. Selected Bond Distances (Å), Bond Angles (deg) and
Torsion Angles (deg) for 3
Bond Distances
Ca(1)-O(11)
Ca(1)-O(13)
P(1)-O(10)
P(1)-O(12)
N(1)‚‚‚O(11)
2.427(4)
2.326(5)
1.654(4)
1.529(5)
3.149(6)
Ca(1)‚‚‚Ca(1)*
5.538(2)
P(1)-O(11)
P(1)-O(13)
N(2)‚‚‚O(12)
1.515(5)
1.510(5)
2.866(7)
Bond Angles
124.8(2)
107.1(2)
101.5(2)
113.5(3)
147.34
Ca(1)-O(11)-P(1)
O(10)-P(1)-O(11)
O(10)-P(1)-O(13)
O(11)-P(1)-O(13)
N(1)-H(1)‚‚‚O(11)
Ca(1)-O(13)-P(1)
O(10)-P(1)-O(12)
O(11)-P(1)-O(12)
O(12)-P(1)-O(13)
N(2)-H(2)‚‚‚O(12)
137.1(3)
104.9(2)
114.2(3)
114.2(3)
151.01
Torsion Angles
C(17)-N(1)-C(12)- 145.3(7) C(18)-N(2)-C(16)-C(11) -143.9(7)
C(11)
The phosphate dianion ligands bridge between two Ca(II) ions
with bond angles of Ca1-O11-P1 and Ca1-O13-P1 as
124.8(2)° and 137.1(3)°, respectively.
Figure 2. (a) Unit structure of [CaII{O3POC6H3-2,6-(NHCOPh)2}(H2O)4-
(EtOH)]n (3). View of the chain structure of [CaII{O3POC6H3-2,6-
(NHCOPh)2}(H2O)4(EtOH)]n (3) from (b) above the yz plane and (c) above
the xz plane (a top view). Ca(II) coordination spheres and the phosphate
groups are presented as blue and pink polyhedrons, respectively. Hydrogen
atoms except for amide NH protons are omitted for clarity.
The phosphate dianion ligands coordinate to Ca(II) ions in a
bridging-bidentate mode, and the unit forms an infinite zigzag-
chain structure. Figure 2 (parts b and c) represents a view from
above the yz and xz plane, respectively, of the one-dimensional
zigzag structure of 3. The ligand is aligned alternatively along
the Ca axis (y axis). The short Ca‚‚‚Ca distance is 5.538(2) Å,
and the longer Ca‚‚‚Ca distance in the same stem is 8.257(7)
Å. Each zigzag chain is covered by the bulky benzoylamino
groups and gives a tubular ligand alley. The distances between
the oxygen atoms of amide carbonyl and the water molecule
coordinated to a Ca(II) ion, O1-O23 and O2-O24, are
2.858(6) and 2.765(9) Å, respectively. These distances imply
that these oxygen atoms are in van der Waals contact with each
other. Each zigzag Ca(II) chain is stacked by intermolecular
9
J. AM. CHEM. SOC. VOL. 124, NO. 6, 2002 1055

A R T I C L E S
Onoda et al.
Table 3. Selected Bond Distances (Å), Bond Angles (deg), and
Torsion Angles (deg) for 4
Bond Distances
Ca(1)‚‚‚Ca(2)
Ca(1)‚‚‚Ca(2)*
Ca(1)-O(12)
Ca(1)-O(22)
Ca(2)-O(12)
Ca(2)-O(22)
Ca(1)-O(31)
P(1)-O(10)
P(1)-O(12)
P(2)-O(20)
P(2)-O(22)
N(1)‚‚‚O(12)
N(3)‚‚‚O(21)
3.705(2)
3.721(2)
2.499(5)
2.356(4)
2.369(4)
2.519(4)
2.325(5)
1.647(4)
1.510(4)
1.646(4)
1.510(4)
3.178(8)
2.883(9)
Ca(1)‚‚‚Ca(1)*
Ca(1)‚‚‚Ca(1)**
Ca(1)-O(13)
Ca(1)-O(23)
Ca(2)-O(13)
Ca(2)-O(23)
Ca(2)-O(41)
P(1)-O(11)
6.020(2)
8.513(2)
2.506(4)
2.367(4)
2.364(4)
2.499(5)
2.296(5)
1.501(5)
1.521(4)
1.507(5)
1.512(4)
2.869)8)
3.195(6)
P(1)-O(13)
P(2)-O(21)
P(2)-O(23)
N(2)‚‚‚O(11)
N(4)‚‚‚O(22)
Bond Angles
Ca(1)-O(12)-P(1)
Ca(1)-O(22)-P(2)
Ca(2)-O(12)-P(1)
Ca(2)-O(22)-P(2)
O(10)-P(1)-O(11)
O(10)-P(1)-O(13)
O(11)-P(1)-O(13)
O(20)-P(2)-O(21)
O(20)-P(2)-O(23)
O(21)-P(2)-O(23)
N(1)-H(1)‚‚‚O(12)
N(3)-H(3)‚‚‚O(21)
95.9(2)
Ca(1)-O(13)-P(1)
Ca(1)-O(23)-P(2)
Ca(2)-O(13)-P(1)
Ca(2)-O(23)-P(2)
O(10)-P(1)-O(12)
O(11)-P(1)-O(12)
O(12)-P(1)-O(13)
O(20)-P(2)-O(22)
O(21)-P(2)-O(22)
O(22)-P(2)-O(23)
N(2)-H(2)‚‚‚O(11)
N(4)-H(4)‚‚‚O(22)
95.3(2)
138.5(2)
140.7(3)
95.51(19)
107.4(3)
102.5(2)
115.8(3)
107.4(3)
102.2(2)
116.2(2)
142.13
141.4(3)
140.0(2)
96.3(2)
104.3(2)
115.8(3)
109.4(3)
105.0(2)
115.2(3)
109.3(3)
137.56
143.53
146.11
Torsion Angles
C(17)-N(1)-C(12)- 144.8(7) C(18)-N(2)-C(16)-C(11) -121.9(8)
C(11)
OH‚‚‚OdC hydrogen bonds with the amide groups to give an
anti parallel alignment.
A recrystallization of 3 in the presence of DMF gives an
octanuclear Ca(II) complex with DMF coordination, [CaII {O3-
8
POC6H3-2,6-(NHCOPh)2}8(OdCHNMe2)8(H2O)12] (4). Figure
3a shows a unit structure for 4, and its selected bond distances
and bond angles are listed in Table 3. All of the Ca(II) ions
have a seven-coordinate structure in pentagonal-bipyramidal
geometry. Four oxygen atoms of the neighboring phosphate
ligand and one water molecule coordinate in equatorial positions.
O31, an amide oxygen of DMF, and O32, an oxygen atom of
a water molecule, exist at each one of the axial positions. The
Ca1-O31 distance (2.325(5) Å) is in the range of the normal
reported distances (2.25-2.34 Å).47-54 The two oxygen atoms
(O12 and O13) of the coordinating ligand are in a monodentate-
bridging mode to two Ca(II) ions: O12 coordinates to Ca1 and
Ca2*, and O13 to Ca1 and Ca2. Each of the phosphate ligands
binds to three Ca(II) ions. Ca1 is coordinated with both O12
and O13 (ca 2.50 Å) in a syn position (Ca-O-P ≈ 95°). The
other two Ca(II) ions, Ca2 and Ca2*, which have shorter Ca-O
distances (2.369(4) and 2.364(4) Å, respectively), lie in the anti
positions (Ca-O-P is av 144.4°).
Figure 3. (a) Unit structure containing Ca1 of [CaII8{O3POC6H3-2,6-
(NHCOPh)2}8(OdCHNMe2)8(H2O)12] (4) and (b) an inner view of the
repeated units of the cyclic-octanuclear Ca(II) structure of 4 with only one
of the ligands together with a DMF molecule. (c) Whole molecular structure.
Ca(II) coordination spheres and the phosphate groups in (c) are presented
as purple and pink polyhedrons, respectively.
Figure 3b shows the octanuclear Ca(II) cluster alternately
coordinated by one of the phosphate oxygen atoms and a DMF.
The octanuclear Ca(II) core has a C4 symmetry and has two
crystallographically nonequivalent Ca(II) ions (Ca1 and Ca2).
This repeated Ca(II) coordination gives a cyclic-octanuclear
structure consisting of a Ca-O-Ca-O diamond core. It has
been reported that a similar diamond chain structure repeats
infinitely due to the planarity of the Ca-O-Ca-O plane,34,35,39
although the plane for 4 is folded by 53° on the O-O axis.
Here, our phosphate ligands and DMF molecules cover the
cyclic Ca ion alley. The units consisting of the Ca(II) ion and
the phosphate ligand are alternatively aligned to form an eight-
membered crown structure including four Ca(II) ions both at
(47) Yu, H.; Zhang, W.; Wu, X.; Sheng, T.; Wang, Q.; Lin, P. Angew. Chem.,
Int. Ed. 1998, 37, 2520-2521.
(48) Rao, C. P.; Rao, A. M.; Rao, C. N. R. Inorg. Chem. 1984, 23, 2080-
2085.
(49) Taeb, A.; Krischner, H.; Kratky, C. Z. Anorg. Allg. Chem. 1987, 545, 191-
196.
(50) Fenske, D.; Baum, G.; Wolkers, H.; Schreiner, B.; Weller, F.; Dehnicke,
K. Z. Anorg. Allg. Chem. 1993, 619, 489-499.
(51) Wunderlich, C. H.; Bergerhoff, G. Z. Kristallogr. 1993, 207, 185-188.
(52) Bergerhoff, G.; Wunderlich, C. H. Z. Kristallogr. 1993, 207, 189-192.
(53) Harrowfield, J. M.; Ogden, M. I.; Richmond, W. R.; White, A. H. J. Chem.
Soc., Dalton Trans. 1991, 2153-2160.
(54) Waters, A. F.; White, A. H. Aust. J. Chem. 1996, 49, 147-154.
9
1056 J. AM. CHEM. SOC. VOL. 124, NO. 6, 2002

Synthesis of Ca(II)- and Na(I) Phosphate Complexes
A R T I C L E S
Table 4. Selected Bond Distances (Å), Bond Angles (deg), and
Torsion Angles (deg) for 5
Bond Distances
Na(1)‚‚‚Na(2)
Na(2)‚‚‚Na(3)
P(1)-O(10)
P(1)-O(12)
P(2)-O(20)
P(2)-O(22)
Na(1)-O(11)
Na(3)-O(4)
Na(3)-O(20)
Na(3)-O(38)
N(1)‚‚‚O(12)
N(3)‚‚‚O(22)
3.326(2)
4.458(2)
1.649(2)
1.522(2)
1.661(2)
1.515(2)
2.407(3)
2.325(3)
2.617(3)
2.516(3)
2.888(3)
3.461(4)
Na(1)‚‚‚Na(3)
3.337(2)
P(1)-O(11)
P(1)-O(13)
P(2)-O(21)
P(2)-O(23)
Na(1)-O(21)
Na(3)-O(11)
Na(3)-O(34)
1.503(2)
1.501(2)
1.501(2)
1.524(3)
2.384(3)
2.457(3)
2.463(3)
N(2)‚‚‚O(13)
N(4)‚‚‚O(23)
2.915(3)
2.876(3)
Bond Angles
O(11)-Na(1)-O(21) 87.02(9) O(11)-Na(1)-O(31) 84.44(10)
O(11)-Na(1)-O(32) 159.85(10) O(11)-Na(1)-O(33) 100.01(9)
O(11)-Na(1)-O(34) 82.63(9)
O(11)-Na(3)-O(38) 90.05(9)
O(21)-Na(2)-O(35) 88.71(10)
O(21)-Na(2)-O(37) 87.09(9)
O(11)-Na(3)-O(34) 82.93(9)
O(21)-Na(2)-O(33) 92.26(10)
O(21)-Na(2)-O(36) 170.99(12)
N(1)-H(1)‚‚‚O(12)
N(3)-H(3)‚‚‚O(22)
149.89
100.72
N(2)-H(2)‚‚‚O(13)
N(4)-H(4)‚‚‚O(23)
147.98
160.23
Torsion Angles
C(17)-N(1)-C(12)- 142.3(3) C(18)-N(2)-C(16)-C(11) -145.1(3)
C(11)
Table 5. Selected IR Bands and CRAMPS NH Chemical Shifts for
Various Phosphate Ligands and Ca(II) Complexesa
-1 a
IR bands (cm
)
CRAMPS (ppm)
ν(OH)
ν(NH)
ν(CdO)
δ NH
1
2b
3
4
5
3430 (br)
3430 (br)
3417 (br)
3418 (br)
3411 (br)
3431
3419
3226 (br)
3221 (br)
3335 (br), 3253 (br)
1690, 1673
1678, 1667
1646
1671
1678, 1650
9.5 (br)
14.1
-
Figure 4. (a) Whole molecular structure and (b) core structure of
(NHEt3)[Na3{O3POC6H3-2,6-(NHCOPh)2}2(H2O)(MeOH)7] (5).
-
13.2
the top and at the bottom (Figure 3c). The diameter of its ring
is 8.513(2) Å, which forms the longest Ca‚‚‚Ca (opposite)
separation. Eight water molecules coordinating to each of the
Ca(II) ions exist inside the Ca(II) cluster ring.
a In the solid state (KBr).
This type of NH‚‚‚O hydrogen bond formation was found in a
Ca(II) phosphate complex with a triphenylacylamino ligand.31
Figure 4 shows the hexanuclear structure with a trinuclear
core of (NHEt3)[Na3{O3POC6H3-2,6-(NHCOPh)2}2(H2O)(Me-
OH)7] (5). A trinuclear core consists of two phosphate dianion
Formation of NH‚‚‚O Hydrogen Bonds in the Solid State.
The selected IR bands of the ν(OH), ν(NH), and ν(CdO) region
for 1, 2b, 3, 4, and 5 in the solid state are listed in Table 5. The
downshifted broad OH bands for 1 and 2b are due to the
formation of hydrogen bonds with CdO or P-O oxygen in the
solid state. The OH bands for 3, 4, and 5 originate from the
water and methanol molecules coordinating to Ca(II) or Na(I)
ions. The amide NH bands of 1 and 2b appear around 3400
cm-1 as free NHs,55 although the NH bands for 3 and 4 shift to
3226 and 3221 cm-1, respectively. The large shifts of ap-
proximate 200 cm-1 from the free NH bands suggest the
presence of strong NH‚‚‚O hydrogen bonds formed in the
phosphate dianion state. Actually, the distance between the two
amide N and phosphate O atoms for 3 and 4 are within the
possible range for hydrogen bonding. The amide ν(CdO)
stretching band of 3 observed at 1646 cm-1 shifts about 24 cm-1
from that of 4. Intermolecular OH‚‚‚OdC hydrogen bonds
between the amide CdO and water molecules exist in the crystal
structure for 3; however, the amide CdO for 4 is free from
hydrogen bonding. The ν(NH) stretching bands for 5 are
observed at 3253 and 3335 cm-1, which are assignable to the
+
ligands, three Na ions and one NHEt3 cation. The distances
of Na1‚‚‚Na2 and Na1‚‚‚Na3 are 3.326(2) and 3.337(2) Å,
respectively (see Table 4). Oxygen atoms from a phosphate
dianion ligand and from methanol coordinate to the Na ions in
µ2 fashion to form a diamond core. The Na1 ion has an
octahedral geometry, but the Na2 ion forms a distorted trigonal
bipyramidal structure simply because the steric repulsion of the
phenyl ring occurs near the Na2 ion. A Na3 ion is ligated with
O11, O34, O38, and O4 in the neighboring trinuclear core with
a distorted tetrahedral geometry and is also weakly coordinated
with O20 and O10. The coordination of the amide carbonyl
oxygen, O4*, results in the dimerization of the trinuclear
structure.
The two uncoordinated oxygen atoms, O12 and O13, are
hydrogen-bonded with amide NH groups. In the other ligands,
the uncoordinated phosphate O22 and O23 atoms are hydrogen-
bonded from ammonium N5H5 and amide N4H4, respectively.
A remarkable point for the coordination geometry for the
phosphate dianion complex 5 is that the negative charge (-1)
of the dianion ligands are compensated for with the double
NH‚‚‚O hydrogen bonds from the amide or the ammonium NHs.
(55) Silverstein, R. M.; Bassler, G. C.; Morrill, T. C. Spectrometric Identification
of Organic Compounds; Wiley: New York, 1981.
9
J. AM. CHEM. SOC. VOL. 124, NO. 6, 2002 1057

A R T I C L E S
Onoda et al.
amide NHs and ammonium NH, respectively.31 The low-
wavenumber shifted bands for 5 are also indicative of the
formation of strong NH‚‚‚O hydrogen bonds in the dianion state.
The amide CdO stretching bands are observed at 1678 cm-1
,
and the shifted bands at ˜1650 cm-1 are thought to originate
from CdO4, which is coordinated to the Na ion.
CRAMPS is often used to detect each proton under different
circumstances in the solid state.56,57 The CRAMPS amide NH
chemical shifts for 1, 2b, and 5 are 9.5, 14.1, and 13.2,
respectively. The downfield shift of the amide NH chemical
shifts also indicates the presence of hydrogen bonds with the
amide groups.
Formation of NH‚‚‚O Hydrogen Bonds in the Solution
State. The formation of NH‚‚‚O hydrogen bonds from the amide
1
NHs to the phosphate in solution was determined by H NMR
spectroscopy. The amide NH chemical shifts for 5, 2b and 1
are observed at 11.56, 10.87, and 10.32 ppm, respectively. The
NH signal in the phosphate monoanion, 2b, appears downshifted
by 0.55 ppm from that in the phosphoric acid state, and the
NH signal in the phosphate dianion complex, 5, was further
shifted (+1.24 ppm). Thus, the NH‚‚‚O hydrogen bonds to the
phosphate oxygen atoms are not likely formed in the phosphoric
acid state and are formed in the phosphate monoanion state.
The stronger hydrogen bonds exist in the phosphate dianion
1
state. The H NMR results are consistent with the IR.
Construction of Novel Metal-Phosphate Structures with
Bulky Amide Ligands. We first constructed the zigzag, cyclic-
octanuclear Ca(II)- and hexanuclear Na(I) phosphate structure
with an unusual metal coordination geometry using bulky amide
ligands. All of the reported Ca(O3POR) or Ca(O3PR) complexes
have polymeric structures, a one-dimensional chain, or a layer
architecture.32,33,36-39 Reported Na phosphate complexes are also
polymeric.40-42 These structures are schematically represented
in Figure 5. The uncoordinated oxygen atom of the PdO bond
tends to form a metal-oxygen bond which produces polymeric
structures. In the complexes shown here, the oxygen atoms of
the phosphate ligands chelate to the metal ions, which exist
between the ligand alleys shown as white boxes (see Figure
5a). We call this kind of metal alley symmetric. The zigzag
Ca(II) complex, 3, has an alternative alley of the phosphate
ligands and a hydrated site shown as black boxes (see Figure
5b). The cyclic-octanuclear Ca(II) complexes, 4, provide a
hydrated site inside the Ca(II) ions, and phosphate ligands are
found outside (Figure 5c). The hexanuclear Na(I) complex, 5,
has the ligands between the trinuclear core, and its outside
coordination site is occupied with methanol molecules (Figure
5d). The bulky benzoylamino ligands occupy the unsymmetric
positions of phosphate ligands. Such an unsymmetric metal-
phosphate ligand unit has been known to be present in the
mononuclear Ca(II) with very bulky triphenylacetylamino
groups, 4 (Figure 5e).31 Our bulky amide ligands enable the
production of an unsymmetric coordination environment because
of steric congestion.
Figure 5. Schematic representation of (a) the one-dimensional structure
of the reported Ca(II) complexes, (b) the zigzag-chain structure found in 3,
(c) the cyclic-octanuclear structure for 4, (d) the hexanuclear structure for
5, and (e) the mononuclear Ca(II) core31 with unsymmetric ligand coordina-
tion. White and black boxes are the organic phosphate and other ligands,
i.e., water molecules and/or methanol.
The infinite zigzag-chain structure of 3 transforms into the
cyclic-octanuclear complex as shown in Figure 6. The reported
transformation of the zinc phosphate structure occurs from a
linear chain into a layer architecture via a ladder structure
Figure 6. Schematic diagram of a structural difference between [CaII{O3-
POC6H3(NHCOPh)2(H2O)4(EtOH)}n (3) and [CaII8{O3POC6H3-2,6-(NH-
COPh)2}8(OdCHNMe2)8(H2O)12] (4).
cooperated with decreasing numbers of the phosphate anion.12,21
The transformation in our Ca(II) complex from a zigzag to a
cyclic structure occurs by the coordination of the amide CdO
(56) Shoji, A.; Kimura, H.; Ozaki, T.; Sugisawa, H.; Deguchi, K. J. Am. Chem.
Soc. 1996, 118, 7604-7607.
(57) Onoda, A.; Yamada, Y.; Doi, M.; Okamura, T.; Ueyama, N. Inorg. Chem.
2001, 40, 516-521.
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1058 J. AM. CHEM. SOC. VOL. 124, NO. 6, 2002

Synthesis of Ca(II)- and Na(I) Phosphate Complexes
A R T I C L E S
of DMF without changing the metal/phosphate ratio. The zigzag-
chains are stacked with each other due to the intermolecular
OH‚‚‚OdC hydrogen bonds involving the amide groups. The
DMF molecule seems to be effective in removing the interac-
tions to the amide CdO. Our bulky amide ligands are able to
convert the formation of the intermolecular and intramolecular
hydrogen bonds. The transformation from the zigzag structure
to the cyclic-octanuclear structure is correlated with the forma-
tion of the intermolecular hydrogen-bond networks.
design with amide groups is an intriguing approach for the
regulation of intramolecular and intermolecular hydrogen bonds.
In conclusion, synthesis of Ca(II) complexes using strategically
designed bulky amide ligands will become very important for
understanding biomineral Ca(II) structures found in biological
systems and also for expanding new Ca(II) cluster chemistry.
Acknowledgment. Support of this work by a JSPS Fellow-
ships [for A.O., Grant 2306 (1999-2002)] and a Grant-in-Aid
for Scientific Research on Priority Area (A) (No. 10146231)
from the Ministry of Education, Science, Sports and Culture,
Japan, is gratefully acknowledged.
Conclusions
Novel zigzag-chain, cyclic-octanuclear Ca(II)- and hexa-
nuclear Na(I) phosphate complexes were synthesized using
bulky amide aryl dihydrogen phosphate ligands. The metal
complexes with bulky amides have a unique unsymmetric ligand
position. The zigzag structure transformed into a cyclic-
octanuclear structure due to the change of coordination of DMF
and the intermolecular hydrogen-bond network. The ligand
Supporting Information Available: X-ray crystallographic
files, in CIF format. This material is available free of charge
via the Internet at http://pubs.acs.org.
JA011457R
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J. AM. CHEM. SOC. VOL. 124, NO. 6, 2002 1059