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M.P. Sternlieb et al. / Polyhedron 28 (2009) 729–732
The product was filtered by aspiration and was washed thrice,
alternating methanol and acetone. Water was also used as a wash
only if preliminary XRD analysis indicated a water-soluble phase.
The product was dried for at least 20 min by aspiration and placed
in a 120 °C oven overnight. Cadmium containing compounds were
dried in a Drierite-filled desiccator.
as NaBaPO4. The insolubility of BaF2 in all solvents probably con-
tributed to the difficulty in obtaining the apatite.
Barium chloroapatite was obtained in anisole using routes B
and C, and in anisole with 18-crown-6 by routes B and C.
The attempted preparation of BaApCl in DMSO, routes A, B, C,
and D yielded Na3PO4, NaBaPO4, an amorphous product, and BaH-
PO4, respectively. In phenol, route C produced BaHPO4. The for-
mation of barium hydrogen phosphate may be due to the protic
nature of phenol and ammonium hydrogen phosphate. Barium
bromoapatite was not prepared successfully in anisole with
18-crown-6 using routes B and C which yielded barium phos-
phate. The preparation of barium hydroxyapatite was unsuccess-
ful in anisole with 18-crown-6 by route B and in pyridine by
route D.
2.2. Analysis
Constituent ions were analyzed qualitatively by first dissolving
the compound in 3 M nitric acid. Phosphate was identified qualita-
tively using 0.5 M ammonium molybdate reagent. Chloride, bro-
mide, and iodide were identified qualitatively with 0.1 M silver
nitrate. The cations were identified qualitatively by standard
methods.
The identities of the products were determined by XRD using a
Philips 3520 XRD system with a monochrometer and a copper X-
ray tube. Phase identity was established using figure of merit
(FOM) values as well as careful visual matching of peaks with those
in the International Center for Diffraction Data (ICDD) PDF-2 Sets
1–44 Inorganics (includes zeolites and minerals) (1994) database.
The presence of fluoride was confirmed by dissolving the sample
in 3 M HNO3, followed by a search for an 19F resonance on a Varian
INOVA 500 MHz NMR spectrometer at 470.12 MHz.
3.3. Cadmium apatites
Cadmium fluoroapatite was obtained using route F in anisole
with 2 mL of glacial acetic acid presumably because cadmium ni-
trate tetrahydrate and sodium phosphate were soluble in anisole
and ammonium fluoride was moderately soluble in glacial acetic
acid. It was identified by 19F NMR and XRD. Cadmium chloroapa-
tite was successfully prepared by route A in a 1:1 anisole and eth-
anol mixture. The purity of the product improved with repeated
washings with distilled water due primarily to the removal of
the NaCl byproduct. The reactions were done in mixed solvents
because sodium phosphate showed the highest solubility in
anisole while cadmium chloride was most soluble in DMSO or
ethanol.
3. Results and discussion
3.1. Nonaqueous syntheses
The synthesis of cadmium fluoroapatite was attempted in
DMSO using route A, but resulted in CdF2. Attempts to prepare
CdApCl using route B in anisole with 18-crown-6 ether produced
a mixture of NaCl and Na3PO4. An attempt using route A in DMSO
produced sodium phosphate. Although CdBr2 is soluble in DMSO,
CdApBr could not be obtained by route A in a 1:1 DMSO and ani-
sole mixture (sodium phosphate was obtained). An attempt at cad-
mium hydroxyapatite by route E in anisole produced sodium
nitrate and Cd(OH)NO3.
Apatites of barium, calcium, cadmium, lead, and strontium were
successfully prepared by the reaction routes shown below, where
M and X are the cation and anion incorporated into M5(PO4)3X
(MApX):
(A) 5MX2 þ 3Na3PO4 ! M5ðPO4Þ3X þ 9NaX
(B) 5MX2 þ 3Na3PO4 ꢀ 12H2O ! M5ðPO4Þ3X þ 9NaX þ 12H2O
(C) 5MX2 þ 3K3PO4 ! M5ðPO4Þ3X þ 9KX
(D) 5MX2 þ 3ðNH4Þ2HPO4 ! M5ðPO4Þ3X þ 6NH4X
(E) 5MðNO3Þ þ 3Na3PO4 þ NaX ! M5ðPO4Þ3X þ 10NaNO3
(F) 5MðNO3Þ2 þ 3Na3PO4 þ NH4X ! M5ðPO4Þ X þ 9NaNO3
3.4. Calcium apatites
2
3
þNH4NO3
(G) 5MX2 þ 3ðCH3OÞ3PO ! M5ðPO4Þ3X þ 9CH3X:
Calcium fluoroapatite was obtained using route F with anisole
and 2 mL glacial acetic acid). Although the XRD of the product indi-
cated a mixture of CaF2 and either the fluoro or hydroxy apatite
(the patterns for the hydroxy- and fluoroapatites are very similar),
the acidic reaction mixture confirms the presence of the fluoroap-
atite. Calcium hydroxyapatite was produced with route E in ani-
sole. Route E, using NaOH, was preferred to the use of calcium
hydroxide for solubility reasons.
Attempts to prepare CaApF using route B in ethanol and route
A in a 1:1 DMSO and anisole mixture resulted in calcium fluoride.
Calcium chloroapatite could not be obtained using route A or B in
ethanol, route A in 1:1 ethanol and anisole mixture, route A in
1:1 ethanol–anisole containing 15-crown-5 ether, and when a
solution of calcium chloride in ethanol was titrated into anisole
with sodium phosphate. In DMSO, route A resulted in sodium
phosphate, route B produced sodium phosphate and sodium chlo-
The solvents differed depending on M and X and no single route
was found to be superior for the preparation of all apatite products.
In addition, product formation could not be predicted solely from
the solubility of the starting materials. Most reactions were run
at 80–120 °C for at least 1 day to increase the dissolution of the
starting materials and the yield of product. Yields ranged from
50% to 70% with no apparent relationship to route or solvent. As
evidenced in a PbApCl synthesis in DMSO, increased temperature
seemed to improve the purity as indicated by a decrease in the
XRD figure of merit values. In many cases, the powder diffraction
pattern contained sharper lines than are routinely obtained using
aqueous methods. The routes and conditions for successful prepa-
rations are summarized in Table 1. The xrd line patterns for PbApF,
prepared using TMP in DMSO, and for BaApCl, prepared in anisole,
are shown in Figs. 1 and 2.
ride, route
D produced NH4HPO4, route A with 2:1 anisole
and DMSO mixture and 18-crown-6 ether resulted in sodium
phosphate. Route A with methanol and 15-crown-5 ether was
attempted because of the solubility of starting materials in
3.2. Barium apatites
The syntheses of barium apatites in DMSO generally require the
absence of sodium ion because of preferential formation of
NaBaPO4. For example, attempted preparation of BaApF in anisole
and 18-crown-6 using route B produced a precipitate identified
this mixture, but resulted in Na2HPO4. Attempts to prepare
CaApOH using route B in anisole with 18-crown-6 ether and in
ethanol produced calcium hydroxide, as did route A in TMP and
DMSO.