Polycations-12. The synthesis of liquid ionic phosphates (lips) from mono- and polycationic ammonium halides

Article abstract of DOI:10.1055/s-2002-33333

Preparations are reported for an extensive series of phosphate salts of polyammonium species from the corresponding halide salts. The phosphate salts, as anhydrous materials, are liquid at or near room temperature. Three approaches for the preparation of these materials are noted, including treatment with aqueous hexafluorophosphoric acid, classical ion exchange methods, and treatment with 85% phosphoric acid. The last of these provides the most desirable results. Several monocationic phosphate salts have also been prepared for comparison with other types of ionic liquids.

Full text of DOI:10.1055/s-2002-33333

1
530
PAPER
Polycations-12. The Synthesis of Liquid Ionic Phosphates (LIPs) from
Mono- and Polycationic Ammonium Halides
a
a
a
a
a
a
a
Synthesis of
L
h
iquid Ionic
P
a
hosphates
r
a
a
a
a
b
Ravinder Raju, Alexander Scumpia, Steve Castro, Robert Engel,* JaimeLee Iolani Cohen*
a
Department of Chemistry and Biochemistry, Queens College, CUNY, 65-30 Kissena Boulevard, Flushing, NY 11367, USA
Fax +1(718)9975198; E-mail: robert_engel@qc.edu
b
Department of Chemistry and Physical Sciences, Pace University, 1 Pace Plaza, New York, NY 10038, USA
Received 19 February 2002; revised 9 May 2002
In the present report, our efforts are particularly con-
cerned with the conversion of a variety of the polyammo-
nium halide species into materials that are liquid at or near
room temperature. Intrigued by the characteristics exhib-
Abstract: Preparations are reported for an extensive series of phos-
phate salts of polyammonium species from the corresponding ha-
lide salts. The phosphate salts, as anhydrous materials, are liquid at
or near room temperature. Three approaches for the preparation of
these materials are noted, including treatment with aqueous ited by room temperature liquid monocationic salts of the
hexafluorophosphoric acid, classical ion exchange methods, and imidazolium and pyridinium types,1
7,19–21
we set out to ex-
treatment with 85% phosphoric acid. The last of these provides the
change the anions of our series of polyammonium halide
salts (as well as several monoammonium halide salts) for
those anions that could possibly result in the formation of
room temperature ionic liquids.
most desirable results. Several monocationic phosphate salts have
also been prepared for comparison with other types of ionic liquids.
Key words: ionic liquid, ammonium, phosphate, molten salt
The preparation of a variety of new room temperature ion-
ic liquids is of significance for a variety of potential appli-
cations for such materials. For liquid ionic phosphates,
these applications include particularly: non-volatile polar
solvents for a wide range of organic reactions (such as
Diels–Alder reactions; media for electrochemical pro-
cesses; non-volatile solvents for extractive purification
procedures; and the construction of electrochemical stor-
age cells.
Ionic liquids are a unique and interesting class of com-
pounds because they are salts that are liquids at or slightly
above room temperature. Their low melting points defy
traditional expectations of the nature of ionic compounds.
The study of ionic liquids has been the focus of consider-
able research activity in recent years because of their po-
tential for a variety of applications. These include new
1
–7
8–13
media for chemical and electrochemical
reactions,
The current
use in separations1
4,15
1,16,17
Our initial efforts toward the preparation of ionic liquids
derived from both mono- and polyammonium salts, were
performed using a standard method for the preparation of
and in catalysis.
focus on achieving cleaner technologies, in both industry
and academia make ionic liquids particularly attractive as
alternatives for the volatile organic solvents currently
22
hexafluorophosphate salts from halide salts. Toward this
end, halide salts of mono- and polyammonium species we
had previously reported, were used.1
1
used as reaction media. Solvents, as Welton states are
8o–t
high on the list of damaging chemicals because they are
used in huge amounts and are usually volatile liquids that
are difficult to contain. On the other hand, ionic liquids are
significantly less volatile and exhibit low flammability,
thereby eliminating vapor-containment problems. They
also exhibit good thermal stability, high ionic conductivi-
ty and are compatible with a wide range of organic and in-
organic materials. This makes them good potential
solvents for thermal and electrochemical reactions. These
liquids are also recyclable (minimizing the accumulation
of waste material). Ionic liquids typically contain large
bulky organic cations and inorganic anions.
This approach for the preparation of hexafluorophosphate
salts, involving treatment of the polyammonium salts with
6
0% aqueous hexafluorophosphoric acid, gave results
seemingly similar to those reported with imidazolium and
22
pyridinium species. That is, a dense white semisolid ma-
terial rapidly separated from the aqueous layer and could
be isolated by filtration. In accord with prior reports for
hexafluorophosphate salts, these materials were relatively
insoluble in water, but were significantly soluble in dime-
thyl sulfoxide, a medium for NMR spectra.
1
13
The H and C NMR spectra (in DMSO-d ) of the collect-
6
Our laboratory has previously reported on the preparation
ed materials corresponded exactly with those observed by
us for the polycationic halide salts (previously reported),
but the 31P NMR spectra indicated that two phosphorus
containing species were present. In addition to the expect-
ed septet at around –144 ppm (relative to 85% phosphoric
acid) for the hexafluorophosphate anion, an additional
singlet was observed near 0 ppm, indicative of simple
phosphate anion. Further, while the amount of simple
1
8
of several series of polycationic organic salts. Included
1
8a–i,18k
herein have been polycationic dendrimeric species,
1
8l–o
polycationic strings,
and several series of polycationic
1
8p,q,t
18s
rings,
including cyclodextrin derivatives.
Synthesis 2002, No. 11, Print: 22 08 2002.
Art Id.1437-210X,E;2002,0,11,1530,1540,ftx,en;M00602SS.pdf.
©
Georg Thieme Verlag Stuttgart · New York
ISSN 0039-7881

PAPER
Synthesis of Liquid Ionic Phosphates (LIPs) from Mono- and Polycationic Ammonium Halides
1531
phosphate anion present in the precipitated material was acid. Both of these approaches for producing pure, virtu-
relatively small (not more than 50% of the amount of the ally anhydrous LIPs involved addition of a charge equiv-
hexafluorophosphate salt), the total formation of recover- alent amount of the phosphoric acid material (85%
able solid was also small. This indicated that a significant aqueous phosphoric acid or crystalline phosphoric acid) to
amount of the initially added cation remained in the aque- a methanolic solution of the polyammonium halide salt.
ous solution.
The reaction mixture was stirred at room temperature un-
der high vacuum until all volatile materials (water, meth-
anol and hydrogen halide) had been removed. This
provided a more reproducible and efficient preparation of
the LIPs than did any of the alternative approaches. Using
High vacuum evaporation of the remaining aqueous solu-
tion and drying of the residue for a week under these con-
ditions resulted in the isolation of a viscous liquid material
which was water soluble and exhibited H and C NMR
spectra (in D O) corresponding exactly with those of the
starting halide salts. However, the P NMR spectra of
these viscous liquids, exhibited only the singlet near 0
ppm corresponding to simple phosphate anion. The H
NMR spectra of freshly dried materials indicated they are
anhydrous within the limits of that technique, although
exposure to room air resulted in the rapid adsorption of
water (This is a characteristic common to the polycationic
1
13
1
the technique of measurement of the H NMR spectrum in
2
3
1
D O with a measured amount of the sodium salt of 3-(tri-
2
methylsilyl)-1-propanesulfonic acid allowed the determi-
nation to be made such that the amount of residual water
present in the freshly prepared materials was less than
1
0
.01% (It should be noted, however, that the LIPs are hy-
groscopic materials and readily accept moisture from ex-
posure to ordinary room air).
salts causing difficulties with their combustion analyses, A large series of LIPs have been produced in this manner,
1
8p–t
Further, testing using halide salts previously reported,18o–t or newly syn-
and has been reported by us before).
of an aqueous solution of the newly isolated materials thesized. Yields and precursors for the newly prepared ha-
1
13
with aqueous silver nitrate solution produced no precipi- lide salts are shown in Table 1, with H and C NMR as
tate, indicating the absence of chloride or bromide ions well as elemental analyses for them shown in Table 2. The
above the limits of detection by that technique (1/ poly- and monocationic LIPs produced, using the 85%
1
00,000).
phosphoric acid approach from newly prepared or previ-
ously reported halide salts are noted in Table 3 with their
P NMR signals.
From these observations we conclude that a new category
of non-aqueous room temperature ionic liquid [specifical-
3
1
ly, liquid ionic phosphates, (LIPs)] have been isolated. A For a selection of these species, thermal stabilities have
survey of the literature concerning room temperature ion- been measured. This involved heating the pure LIP at
ic liquids shows no prior reports of phosphate salts of or- 165 °C for a period of 4 hours followed by remeasurement
1
13
31
ganic cations exhibiting these characteristics.
of the H, C and P NMR spectra. The results of these
experiments are shown in Table 4, where ‘excellent’ indi-
cates that no decomposition could be detected through the
NMR spectra, ‘mediocre’ indicates some small amount of
decomposition (<5%) could be detected, and ‘poor’ indi-
cates that significant amounts of decomposition products
could be noted by NMR techniques.
As the approach to the preparation of LIPs using 60%
aqueous hexafluorophosphoric acid results in the forma-
tion of a significant amount of the hexafluorophosphate
salt species, an alternative method for the preparation of
the LIPs was sought. For a variety of potential applica-
tions, the liquid ionic phosphates are more favorable than
their hexafluorophosphate counterparts. While the release Solubilities of a selection of the newly prepared LIPs have
of phosphate anion into the environment poses a problem also been measured. These are indicated in Table 5. The
(
overfertilization of aquatic plant life), it avoids a very indications in Table 5 are as follows: I <–0.01 g of LIP
significant hazard associated with the release of hexafluo- dissolves in 10 mL of solvent; M – 0.01–0.05 g of LIP dis-
rophosphate anion into the same environment. Specifical- solves in 10 mL of solvent; S >–0.05 g of LIP dissolves in
ly, hexafluorophosphate anion will undergo hydrolysis 10 mL of solvent. Fundamentally, as opposed to non-
yielding phosphate and hydrogen fluoride. In fact, such aqueous ionic liquids wherein the anion is hexafluoro-
release of hexafluorophosphate anion produces more phosphate, the LIPs exhibit significant solubility in water
phosphate per mole of ionic liquid than do the liquid ionic and alcohol media. Solubility in hydrocarbon media is not
phosphates, along with the significantly more hazardous observed, and only partial solubility is noted in halogenat-
hydrogen fluoride.
ed organic solvents and other polar organic media, includ-
ing acetonitirle, which serves as a workable solvent for the
polycationic halide salts. As such, the LIPs constitute an
intriguing category of room temperature ionic liquid with
chemical and physical characteristics significantly differ-
ent from those otherwise available. Other aspects of their
physical and chemical characteristics (conductivity, diffu-
sion characteristics, and catalytic capabilities) will be con-
sidered in further reports.
An initial attempt at an alternative approach involved the
use of DOWEX anion exchange resins, in an attempt at
classical exchange of PO4 for halide ion. While this ap-
proach proved successful in certain instances, it did not in
others, leaving significant amounts of salt remaining in
the halide form.
3
–
Further attempts to modify the preparation of LIPs from
parent halide salts centered on their treatment with either
8
5% aqueous phosphoric acid or crystalline phosphoric
Synthesis 2002, No. 11, 1530–1540 ISSN 0039-7881 © Thieme Stuttgart · New York

1
532
S. Lall et al.
PAPER
Table 1 Yields of Newly Synthesized Halide Salts (RX + Nu:)
Compound No. Halide Reactant
Amine Reactant
Yield (%)
1
2
3
4
5
6
7
benzyl bromide
4-bromo-1-butene
allyl bromide
1,4-diazabicyclo[2.2.2]octane
1,4-diazabicyclo[2.2.2]octane
pyridine
91
63
74
65
77
72
68
benzyl bromide
iodomethane
pyridine
4-(dimethylamino)pyridine
4-(dimethylamino)pyridine
2,3-(dimethylamino)-1-propanol
6-chloro-1-hexanol
1,9-dichlorononane
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
1,10-dichlorodecane
2,3-(dimethylamino)-1-propanol
71
83
70
88
65
85
76
58
61
68
84
59
74
66
43
82
87
79
59
1,3-bis(bromomethyl)benzene
1,4-bis(bromomethyl)benzene
1,2-bis(bromomethyl)benzene
1,2-bis(2-chloroethoxy)ethane
1,2-bis(bromomethyl)benzene
1,3-bis(bromomethyl)benzene
1,4-dichloro-2-butyne
2,3-(dimethylamino)-1-propanol
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
2,3-(dimethylamino)-1-propanol
2,3-(dimethylamino)-1-propanol
(2) 1,4-diazabicyclo[2.2.2]octane
(2) 1,4-diazabicyclo[2.2.2]octane
(2) 1,4-diazabicyclo[2.2.2]octane
(2) 1,4-diazabicyclo[2.2.2]octane
2,2 -bis(bromomethyl)-1,1 -biphenyl
iodomethane
(2) 1,4-diazabicyclo[2.2.2]octane
2
iodomethane
1
4-bromo-1-butene
1
3-chloro-1-propanol
1
allyl bromide
2
1,10-dichlorodecane
pyridine
1,3-bis(bromomethyl)benzene
1,2-bis(chloromethyl)benzene
1,2-bis(chloromethyl)benzene
1,3-bis(bromomethyl)benzene
methylimidazole
1,4-bis(dimethylamino)butane
12
15
Table 2 NMR Spectra and Analyses of Newly Synthesized Halide Salts
1
13
Comound
No.
H NMR Spectrum (D O
)
C NMR Spectrum (D O
)
Elemental Analysis
2
2
1
2.95 (m, 6 H), 3.24–3.28 (m, 6 H), 4.69 46.63, 54.44, 70.86, 127.42, 131.14,
s, 2 H), 7.36–7.48 (m, 5 H) 132.33, 132.38
Anal. Calcd for C H N Br H O: C,
13 19 2 2
55.13; H, 6.76. Found: C, 55.20; H, 6.82
(
2
2.54 (m, 2 H), 3.14 (m, 6 H), 3.32 (m, 24.42, 42.70, 50.76, 61.90, 117.20,
H), 3.39 (m, 6 H), 5.16 (m, 2 H), 5.71 130.89
m, 1 H)
Anal. Calcd for C H N Br 2H O: C,
42.41; H, 8.19. Found: C, 42.34; H 7.00
10
19
2
2
2
(
3
5.14 (d, J = 6), 2 H) 5.44 (m, 2 H),
122.36, 122.50, 129.15, 143.46, 145.17
Anal. Calcd for C H NBr 3H O:
8
10
2
6
8
2.61,6.05 (m, 1 H), 8.01 (m, 2 H),
.48 (m, 1 H), 8.76 (m, 2 H)
C,37.81; H, 6.35. Found: C, 37.95; H,
6.28
Synthesis 2002, No. 11, 1530–1540 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Synthesis of Liquid Ionic Phosphates (LIPs) from Mono- and Polycationic Ammonium Halides
1533
Table 2 NMR Spectra and Analyses of Newly Synthesized Halide Salts (continued)
1
13
Comound
No.
H NMR Spectrum (D O
)
C NMR Spectrum (D O
)
Elemental Analysis
2
2
4
4.71 (s, 2 H) 7.33, br, 5 H), 7.91 (m, 2 67.00, 130.84, 131.55, 132.05, 132.42,
Anal. Calcd for C H NBr H O:
12
12
2
H) 8.39 (m, 1 H), 8.74 (m, 2 H)
135.18, 146.67, 148.44
C,53.75; H, 5.26. Found: C, 53.49; H,
.51
5
5
6
3.08 (s, 6 H), 3.79 (s, 3 H), 7.29
39.81, 44.52, 107.78, 142.50, 156.46
Anal. Calcd for C H N I H O: C, 34.06;
8 13 2 2
H, 5.36. Found: C, 33.85; H, 5.49
(
AA BB , 4 H)
1.24 (m, 4 H), 1.43 (m, 2 H), 1.80 (m, 24.60, 25.10, 29.92, 31.11, 39.42, 57.69, Anal. Calcd for C H N OCl 2H O: C,
13
23
2
2
2
4
H), 3.14 (s, 6 H), 3.52 (t, J = 7, 2 H), 61.68, 107.58, 141.416, 156.453
.07 (t, J = 7, 2 H), 7.94 (AA BB , 4 H)
52.96; H, 9.23. Found: C, 52.71; H, 9.40
7
8
9
1.25 (br, 14 H), 1.68 (m, 4 H), 1.91 (m, 24.10, 27.20, 27.72, 30.41, 30.58, 52.91, Anal. Calcd for C H N O Cl 3H O:
19 44 2 2 2 2
4
H), 2.99 (s, 12 H), 3.23 (t, J = 6), 4
60.50, 63.71
C, 49.88; H, 11.02 Found: C, 50.03; H,
10.94
H), 3.31(t, (J = 6), 4 H), 66.553.61(t,
J = 6), 4 H
1.20 (br, 16 H) 1.64 (m, 4 H), 1.87 (m, 22.13, 25.21, 25.75, 28.45, 28.62, 50.92, Anal. Calcd for C H N O Cl H O: C,
20
46
2
2
2
2
4
H), 2.95 (s, 12 H) 3.18 (t, J = 4), 4
58.50, 61.70
55.16; H, 11.11. Found: C, 55.01; H,
11.36
H), 3.25 (t, J = 4), 4 H), 64.543.56 (t,
J = 6), 4 H
2.04 (m, 4 H), 2.98 (s, 12 H), 3.34 (t,
25.38, 50.04, 58.50, 62.41, 128.50,
Anal. Calcd for C H N O Br 2H O:
18
34
2
2
2
2
J = 4), 4 H), 3.61 (t, J = 4, 4 H), 67.70, 130.46, 135.53, 137.41
.50 (s, 4 H), 7.63 (m, 4 H)
C, 45.58; H, 8.07. Found: C, 45.52; H,
8.11
4
1
1
0
1
2.00 (m, 4 H), 2.95 (s, 12 H), 3.33 (m, 25.72, 50.51, 58.82, 67.72, 67.82,
H), 3.57 (m, 4 H), 4.52 (s, 4 H), 7.61 130.33, 134.27
s, 4 H)
Anal. Calcd for C H N O Br : C,
42.70; H, 7.56. Found: C, 42.73; H, 7.20
18
34
2
2
2
4
(
2.00 (m, 4 H), 2.93 (s, 12 H), 3.40(t,
25.45, 49.62, 58.48, 62.82, 64.79,
128.81, 131.97, 135.67
Anal. Calcd for C H N O Br H O: C,
1
8
34
2
2
2
2
J = 5), 4 H), 3.42 (t, J = 5, 4 H), 4.80
44.28; H, 7.43. Found: C, 44.02; H, 7.68
(s, 4 H), 7.67 (m, 4 H)
1
1
1
1
1
1
2
3
4
5
6
7
3.14 (t, J = 7), 12 H), 3.44 (m, 18 H),
46.22, 55.08, 65.30, 65.37, 71.63
Anal. Calcd for C H N O Cl H O: C,
41.20; H, 7.01. Found: C, 41.36; H, 7.12
18
36
4
2
2
2
3.66 (s, 4 H), 3.93, br, 4 H)
3.03 (br, 12 H), 3.58 (br, 12 H), 4.80 (s, 71.52, 78.70, 92.14, 154.42, 159.64,
Anal. Calcd for C H N Br 3H O: C,
20
32
4
2
2
4
H), 7.66 (br, 4 H) 163.31
44.29; H, 7.06. Found: C, 44.12, H, 7.22
3.15 (br, 12 H), 3.44 (br, 12 H), 4.54 (s, 43.31, 51.13, 66.62, 126.28, 129.30,
H), 7.60 (br, 4 H) 134.44, 136.34
Anal. Calcd for C H N Br 2H O: C,
20
32
4
2
2
4
45.81; H, 6.92. Found: C, 45.73; H, 7.07
3.10 (br, 12 H) 3.16 (s, 4 H), 3.31 (br, 42.28, 50.51, 51.88, 78.35
2 H)
Anal. Calcd for C H N Cl H O: C,
16
28
4
2
2
1
52.60; H, 8.28. Found: C, 52.47; H, 8.36
3.17–3.40 (br, 24 H), 4.04 (d, J = 13, 2 45.32, 52.72, 67.08, 124.36, 131.13,
H) 4.71 (d, J = 13, 2 H), 7.70 (m, 8 H) 133.75, 134.19, 136.18, 142.96
Anal. Calcd for C H N Br H O: C,
26
36
4
2
2
53.62; H, 6.58. Found: C, 53.30; H, 6.87
2.65 (m, 2 H), 3.37 (s, 3H), 3.68 (m, 2 27.50, 52.66, 53.89, 54.49, 65.48,
H), 4.04 (br, 12 H), 5.23 (m, 2 H), 5.77 120.82, 132.61
Anal. Calcd for C H N BrI 3H O: C,
11
22
2
2
29.81; H, 6.37. Found: C, 29.65; H, 6.44
(
m, 1 H)
1
1
8
9
3.29 (s, 3 H), 3.95 (s, 12 H), 4.77 (s, 2 78.26, 80.24, 80.91, 96.38, 132.18,
H), 7.52 (br, 5 H) 157.25, 159.16, 160.56
Anal. Calcd for C H N BrI H O: C,
37.94; H, 5.46. Found: C, 37.78; H, 5.61
14
20
2
2
2.53 (m, 2 H), 3.58 (m, 2 H), 3.94 (br, 26.49, 51.08, 51.74, 64.47, 69.24,
Anal. Calcd for C H N Br 4H O: C,
17
26
2
2
2
1
5
2 H), 4.73 (s, 2 H), 5.16 (m, 2 H),
.70 (m, 1 H), 7.52 (m, 5 H)
119.80, 125.18, 130.03, 131.61, 131.98, 41.65; H, 6.99 Found: C, 41.33; H, 7.25
133.28
2
0
2.03 (m, 2 H), 3.67 (br, 4 H), 3.92 (br, 23.32, 49.64, 50.22, 56. 62, 61.87, 67.80, Anal. Calcd for C H N OBrCl 2H O:
16 26 2 2
1
2 H) 4.78 (s, 2 H), 7.55 (br, 5 H)
123.72, 128.56, 130.51, 131.82
C, 46.44; H, 7.31 Found: C, 46.53; H
.99
6
Synthesis 2002, No. 11, 1530–1540 ISSN 0039-7881 © Thieme Stuttgart · New York

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S. Lall et al.
PAPER
Table 2 NMR Spectra and Analyses of Newly Synthesized Halide Salts (continued)
1
13
Comound
No.
H NMR Spectrum (D O
)
C NMR Spectrum (D O
)
Elemental Analysis
2
2
2
1
2.55 (m, 2 H), 3.57 (m, 2 H), 3.92 (br, 24.85, 49.46, 50.05, 62.72, 65.65,
Anal. Calcd for C H N Br 2H O: C,
13 24 2 2 2
1
5
2 H), 4.11 (m, 2 H), 5.16 (m, 2 H),
.67 (m, 3 H),5.92 (m, 1 H)
118.14, 121.01, 129.95, 130.13
38.63; H, 6.98 Found: C, 38.84; H 6.68
2
2
1.16 (br, 12 H), 1.68 (br, 4 H), 4.46 (t, 25.46, 28.29, 28.56, 30.80, 128.51,
J = 7, 4 H), 7.93 (m, 2 H) 62.28, 8.40 144.46, 145.81
m, 1 H), 8.69 (m, 2 H)
Anal. Calcd for C H N Cl 4H O: C,
54.42; H, 8.68 Found: C, 54.47; H, 8.90
20
30
2
2
2
(
2
2
3
4
3.80 (s, 6 H), 5.33 (s, 4 H), 7.38 (m, 8 33.77, 50.56, 120.22, 122.87, 126.30,
Anal. Calcd for C H N Br H O: C,
43.07; H, 4.97. Found: C, 42.95; H 5.13
16
20
4
2
2
H), 8.66 (s, 2 H)
127.22, 128.21, 132.64, 134.14
1.70 (br, 4 H), 2.96–3.03 (m, 12 H)
16.92, 18.56, 48.15, 48.43, 63.28,
Anal. Calcd for C H N Cl 3H O: C,
16
28
2
2
2
3
.68 (m, 4 H), 4.84 (s. 4 H), 7.67 (br, 4 127.56, 130.44, 134.54
49.75; H, 9.89 Found: C, 49.81; H, 10.02
H)
2
2
5
6
3.56–3.61 (br, 4 H), 3.62–3.66 (br, 4
H), 3.97 (br, 32 H), 7.64 (s, 4 H)
44.14, 51.20, 52.43, 63.74, 64.87, 68.16, Anal. Calcd for
128.53, 134.53 C H N O Br Cl 2H O: C, 41.78; H,
2
6
44
4
2
2
2
2
7
.01 Found: C, 41.49; H, 7.35
4.08 (s, 24 H), 4.74 (s, 4 H), 4.86 (s, 4 48.86, 49.68, 52.71, 61.11, 78.10,
H), 7.46–7.76 (m, 4 H) 124.44, 129.11, 134.11, 135.05
Anal. Calcd for C H N Br Cl H O: C,
2
4
36
4
2
2
2
45.81; H, 6.09. Found: C, 45.94; H, 6.01
Table 3 Newly Synthesized Phosphate Salts
Table 3 Newly Synthesized Phosphate Salts (continued)
Com- Structure
pound
No.
Halide 31P
Precur- NMR
Com- Structure
pound
No.
Halide 31P
Precur- NMR
sor
( , D O)
sor
( , D O)
2
2
2
7
Ref.4
1.07
3
3
3
4
5
6
2
1.11
1.22
1.13
17
18
2
2
3
3
8
9
0
1
Ref.4
1.18
1.02
1.10
1.15
3
4
5
3
7
19
1.19
3
3
8
9
20
1.22
1.16
1.06
21
3
3
2
3
6
1
1.16
1.10
40
Ref.10
Synthesis 2002, No. 11, 1530–1540 ISSN 0039-7881 © Thieme Stuttgart · New York

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Synthesis of Liquid Ionic Phosphates (LIPs) from Mono- and Polycationic Ammonium Halides
1535
Table 3 Newly Synthesized Phosphate Salts (continued) Table 3 Newly Synthesized Phosphate Salts (continued)
Com- Structure
pound
No.
Halide 31P
Precur- NMR
Com- Structure
pound
No.
Halide 31P
Precur- NMR
sor
( , D O)
sor
( , D O)
2
2
4
4
4
1
2
3
7
1.20
1.19
1.21
47
10
1.16
8
4
8
Ref.10
1.27
Ref.10
Ref.10
4
5
9
0
1.28
1.05
15
12
4
4
Ref.10
0.97
5
1
1.10
4
5
11
1.16
5
2
13
1.20
4
6
9
1.17
5
3
14
1.18
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S. Lall et al.
PAPER
Table 3 Newly Synthesized Phosphate Salts (continued)
Table 3 Newly Synthesized Phosphate Salts (continued)
Com- Structure
pound
No.
Halide 31P
Precur- NMR
Com- Structure
pound
No.
Halide 31P
Precur- NMR
sor ( , D O)
sor
( , D O)
2
2
5
4
23
1.18
61
Ref.18q 1.18
Ref.18q 1.20
Ref.18q 2.91
6
6
2
3
5
5
5
6
22
1.10
Ref.18p 1.59
6
4
Ref.18p 1.22
5
7
Ref.18p 3.91
6
5
24
1.12
5
8
Ref.18t 1.23
6
6
Ref.18t 1.15
5
6
9
0
Ref.18p 1.18
Ref.18p 1.21
Synthesis 2002, No. 11, 1530–1540 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Synthesis of Liquid Ionic Phosphates (LIPs) from Mono- and Polycationic Ammonium Halides
1537
Table 3 Newly Synthesized Phosphate Salts (continued) Table 3 Newly Synthesized Phosphate Salts (continued)
Com- Structure
pound
No.
Halide 31P
Precur- NMR
Com- Structure
pound
No.
Halide 31P
Precur- NMR
sor ( , D O)
sor
( , D O)
2
2
6
7
Ref.18t 1.24
72
Ref.18t 0.17
7
3
26
1.12
6
8
Ref.18t 1.08
7
4
Ref.18s 3.86
6
7
7
9
0
1
Ref.18p 1.25
7
5
Ref.18s 1.05
Ref.18p 1.20
Table 4 Thermal Stability of LIPs upon Heating to 165 °C for 4
Hours
Compound
25
1.16
Excellent - No decomposition noted
2
2
7
8
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S. Lall et al.
PAPER
Table 4 Thermal Stability of LIPs upon Heating to 165 °C for 4
Table 4 Thermal Stability of LIPs upon Heating to 165 °C for 4
Hours (continued)
Hours (continued)
Compound
Compound
4
4
0
1
43
Poor
3
4
5
5
4
5
2
6
4
6
6
1
5
6
9
4
Mediocre
2
3
9
0
3
3
2
3
Synthesis 2002, No. 11, 1530–1540 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Synthesis of Liquid Ionic Phosphates (LIPs) from Mono- and Polycationic Ammonium Halides
1539
Table 4 Thermal Stability of LIPs upon Heating to 165 °C for 4
masses of the reagents) in a flask fitted with a magnetic stirrer. The
Hours (continued)
reaction mixture was stirred at ambient temperature for 48 h, the re-
sultant precipitate was collected by suction filtration through sin-
Compound
tered glass, washed with MeCN and anhyd Et O, and dried under
2
high vacuum.
Dihaloalkanes with an Equivalent Amount of Di(tertiary)amine
7
5
(
24–26)
The dihaloalkane (1 equiv) with the appropriate di(tertiary)amine (1
equiv) were combined with MeCN (10 the combined masses of
the reagents) in a flask fitted with a magnetic stirrer and oil bath and
were stirred while heating at reflux for 48 h. The resultant precipi-
tate was collected by suction filtration, washed with MeCN, anhyd
Et O, and dried under high vacuum. For 25 and 26, additional wash-
2
ing with hot MeCN was necessary to remove the remaining unreact-
ed di(tertiary)amine reagent.
Dihaloalkanes with an Excess of Di(tertiary)amine (12–16)
The dihaloalkane (1 equiv) with the di(tertiary)amine, 1,4-diazabi-
cyclo[2.2.2]octane (4 equiv), were combined with MeCN (10 the
combined masses of the reagents) in a flask fitted with a magnetic
stirrer. The reaction mixture was stirred at ambient temperature for
48 h, the resultant precipitate was collected by suction filtration,
All chemicals used in syntheses, purification, and comparison anal-
yses were of commercial reagent quality and were used without pu-
rification. The parent solid halide salts were prepared as previously
reported.1 All NMR spectra were measured using a Brüker 400
8j–t
MHz DPX400 instrument in D O soln at r.t. Elemental analyses of
washed with MeCN, anhyd Et O, and dried under high vacuum.
2
2
the parent salts previously reported were performed by Schwarzko-
pf Microanalytical Laboratory, Woodside, NY.
LIPs Using 60% aq HPF ; General Procedure
6
The cationic (or polycationic) halide salt (1 equiv) was dissolved in
Halide Salts; General Procedure
H O (6 the mass of the salt) and cooled in an ice bath. To the mix-
2
Monohaloalkanes with Di(tertiary)amines (1,2) and Monoha-
loalkanes with Mono(tertiary)amines (3–6,17–21)
ture, was added, dropwise with stirring, a 60% aq soln of hexafluo-
rophosphoric acid (1 equiv of HPF ) and stirring continued with
6
The monohaloalkane (1 equiv) with the appropriate di(tertia-
ry)amine (1 equiv) or mono(tertiary)amine (1 equiv) were com-
bined with EtOAc (4 the combined masses of the reagents) in a
flask fitted with a magnetic stirrer. The reaction mixture was stirred
at ambient temperature for 48 h. the resultant precipitate was col-
lected by suction filtration through sintered glass, washed with
cooling for 16 h. The resultant solid was collected by suction filtra-
tion through sintered glass, washed with H O (500 mL), and dried
2
1
13
under high vacuum. Measurement of H and C NMR in DMSO-d6
soln indicated the organic cation portion of this product to be iden-
3
1
tical to that of the halide salt initially used; P NMR of the same
3
material indicated the presence of both PF6 anion and the PO4 an-
EtOAc, anhyd Et O, and dried under high vacuum.
ion. Evaporation of the filtrate, first with a rotary evaporator and
2
then with high vacuum, produced a viscous liquid (soluble in D O,
2
1
13
Dihaloalkanes with Mono(tertiary)amines (7–11,22,23)
The dihaloalkane (1 equiv) with the appropriate mono(tertia-
ry)amine (2 equiv) were combined with MeCN (4 the combined
that exhibited identical H and C NMR spectra to those measured
for the PF6 and halide salts, but exhibited only the PO4 signal in
3
Table 5 Solubility Characteristics of Newly Synthesized LIPs
Solvent
LIP
2
I
7
30
I
32
I
45
I
56
I
67
I
68
I
73
I
Hexane
Toluene
CHCl3
I
I
I
I
I
I
I
I
S
I
I
I
M
I
I
M
I
M
I
CH Cl2
S
M
I
M
I
I
I
2
Ethyl acetate
Acetone
M
M
S
I
I
I
I
I
I
I
I
M
I
I
M
I
I
CH CN
I
I
I
I
I
3
Ethanol
Water
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
I
S
S
S
S
S
S
S
Methanol
S
S = soluble, M = sparingly soluble, I = insoluble
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1
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S. Lall et al.
PAPER
the 31P NMR spectrum. The H NMR spectrum also exhibited vari-
1
(10) Slocum, D. W.; Edgecombe, A. L.; Fowler, J. S.; Gibbard,
able amounts of H O to be present in the samples.
H. F.; Phillips, J. Organometallics 1990, 9, 307.
2
(
11) Hussey, C. L.; King, L. A.; Wilkes, J. S. J. Electroanal.
Chem. 1979, 102, 321.
LIPs using 85% H PO ; General Procedure
3
4
The cationic (or polycationic) halide salt (1 equiv) was dissolved in
MeOH (6 the mass of the salt used) and to it was added either 85%
aq phosphoric acid or crystalline phosphoric acid (1 charge equiv
based on PO43 and the charge of the cationic portion of the salt).
The reaction mixture was heated at reflux for 24 h, all volatile ma-
terials were evaporated, first using a rotary evaporator, and then
with high vacuum for a week. The resultant viscous liquid was sol-
(12) Pickup, P. G.; Osteryoung, R. A. J. Am. Chem. Soc. 1984,
106, 2294.
(13) Laher, T. M.; Hussey, C. L. Inorg. Chem. 1983, 22, 1279.
(14) Visser, A. E.; Swatloski, R. P.; Rogers, R. D. Green Chem.
2000, 1.
(15) Huddleston, J. G.; Willauer, H. D.; Swaltloski, R. P.; Visser,
A. E.; Rogers, R. D. Chem. Commun. 1998, 1765.
(16) Sheldon, R. Chem. Commun 2001, 2399.
1
13
31
uble in D O and exhibited H, C and P NMR spectra in accord
2
with the structure of the initially used cationic portion associated
with phosphate anion. Measurement of the H NMR spectrum using
(17) Carmichael, H. Chem. Br. 2000, January, 36.
(18) (a) Rengan, K.; Engel, R. J. Chem Soc., Chem. Commun.
1990, 1084. (b) Rengan, K.; Engel, R. J. Chem. Soc., Perkin
Trans. 1 1991, 987. (c) Engel, R.; Rengan, K.; Milne, C.
Polym. Prepr. 1991, 32, 601. (d) Engel, R. Polym. News
1992, 17, 301. (e) Rengan, K.; Engel, R. J. Chem. Soc.,
Chem. Commun. 1992, 757. (f) Engel, R.; Rengan, K.;
Chan, C.-S. Phosphorus Sulfur Relat. Elem. 1993, 77, 221.
1
D O and a measured amount of the sodium salt of 3-(trimethylsilyl)-
2
1
-propanesulfonic acid present allowed the determination to be
made that the contamination by H O of freshly prepared samples
2
was less than 0.01%.
Acknowledgement
(
g) Engel, R.; Rengan, K.; Chan, C.-S. Heteroat. Chem.
1
2
3
993, 4, 181. (h) Engel, R. Adv. Dendritic Macromol. 1995,
, 73. (i) Cherestes, A.; Engel, R. Polym. Commun. 1994,
5, 3343. (j) Fabian, J.; October, T.; Cherestes, A.; Engel, R.
For financial support of this effort we wish to thank: the NYC-AMP
Program, the PSC-BHE Research Award Program, and the ICET
Corporation. We also wish to thank the NYC-AMP Program for fel-
lowship support for one of us (JIC). We would also like to thank Dr.
Gopal Subramanian for his assistance with the NMR techniques
used.
Synlett 1997, 1007. (k) Cherestes, A.; October, T.; Engel, R.
Heteroat. Chem. 1998, 9, 485. (l) Shevchenko, V.; Engel, R.
Heteroat. Chem. 1998, 9, 495. (m) Strekas, T. C.; Engel, R.;
Locknauth, K.; Cohen, J.; Fabian, J. Arch. Biochem.
Biophys. 1999, 364, 129. (n) Engel, R.; Shevchenko, V.;
Lall, S.; Tropp, B.; Lau, N.; Strekas, T. Phosphorus, Sulfur
Silicon Relat. Elem. 1999, 147, 83. (o) Cohen, J. I.;
Traficante, L.; Schwartz, P. W.; Engel, R. Tetrahedron Lett.
1998, 39, 8617. (p) Cohen, J. I.; Rusinowski, A.; Strekas, T.
C.; Engel, R. Heteroat. Chem. 1999, 10, 559. (q) Cohen, J.
I.; Engel, R. Synth. Commun. 2000, 30, 2161. (r) Cohen, J.
I.; Engel, R. Res. Trends 2000, 7, 151. (s) Cohen, J. I.;
Castro, S.; Han, J.-A.; Shteto, V.; Engel, R. Heteroat. Chem.
2000, 11, 546. (t) Cohen, J. I.; Shteto, V.; Engel, R.
Synthesis 2000, 1263.
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Synthesis 2002, No. 11, 1530–1540 ISSN 0039-7881 © Thieme Stuttgart · New York