Properties of onium salts of phosphorus and nitrogen

Article abstract of DOI:10.1007/s11176-005-0370-3

Ammonium and phosphonium halides when heated with excess dimethyl or diethyl phosphite can undergo anion exchange as a result of alkylation of halide ions with dialkyl phosphites. Experimental data were obtained, that cast some doubt in the commonly accepted opinion that reactions of tertiary amines and phosphines with dihalides in apolar media result in exclusive formation of monosalts. 2005 Pleiades Publishing, Inc.

Full text of DOI:10.1007/s11176-005-0370-3

Russian Journal of General Chemistry, Vol. 75, No. 7, 2005, pp. 1074 1076. Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 7, 2005,
pp. 1137 1139.
Original Russian Text Copyright
2005 by Ovakimyan, Barsegyan, Kikoyan, Indzhikyan.
Properties of Onium Salts of Phosphorus and Nitrogen
M. Zh. Ovakimyan, S. K. Barsegyan, N. M. Kikoyan, and M. G. Indzhikyan
Institute of Organic Chemistry, National Academy of Sciences of Armenia, Erevan, Armenia
Received March 11, 2004
Abstract Ammonium and phosphonium halides when heated with excess dimethyl or diethyl phosphite
can undergo anion exchange as a result of alkylation of halide ions with dialkyl phosphites. Experimental
data were obtained, that cast some doubt in the commonly accepted opinion that reactions of tertiary amines
and phosphines with dihalides in apolar media result in exclusive formation of monosalts.
It was previously shown that (1-alkoxy-2-bromo-
ethyl)phosphonium salts, unlike other phosphonium
salts, undergo thermolysis at low temperatures to form
triphenylphosphine oxide as a phosphorus-containing
product [1]. It was proposed that these reactions are
driven by coordination of the alkoxyl oxygen with
onium phosphorus atoms and by the presence of the
triphenylphosphonium salt and dimethyl phosphite.
However, heating of (1-alkoxyvinyl)triphenylphos-
phonium salts with excess dimethyl phosphite un-
expectedly gave a phosphorus-containing nonhalo-
1
genated salt whose H NMR spectrum diplayed, along
with characteristic signals of the phosphonium cation
of the starting salt, a doublet at 3.50 ppm, assignable
to the POCH3 group, and a PH doublet with a coupl-
ing constant of 650 Hz. These results led us to con-
clude that bromine had exchanged for a methyl
readily leaving bromine atom
to phosphorus.
Proceeding with this research, we made an attempt
to prepare a 2-phosphorylated analog of (1-alkoxy-2-
bromoethyl)phosphonium salts from a (1-butoxyvinyl)- hydrogen phosphite anion.
O
Ph3P+ C=CH2 + (CH3O)2P
Ph3P+ C=CH2
O
CH3Br
H
CH3O
H
Br
OR
OR
P
O
R = C2H5, C4H9.
Similar halide exchange we also observed with
methyltriphenylphosphonium bromide that was used
as an example of a compound containing no double
bonds. However, we failed to obtain a diphosphonium
salt with two methyl hydrogen phosphite anions.
When heated with a fourfold excess of dimethyl
phosphite, ethylenebis(triphenylphosphonium) di-
bromide completely decomposed, and dimethyl phos-
phite converted into an acid. After treatment of the
reaction mixture with alkali we isolated triphenyl-
phosphine oxide. Probably, the decomposition of the
salt with a loss of the ethylene bridge had been
preceded by anion exchange by the following
scheme.
H
O
O
H
O
O
O
H
P
P
(CH3O)2P
OCH3
OCH3
Ph3P+ CH2CH2 P+Ph3
Br
Ph3P+ CH2CH2 P+Ph3
Ph3P=O + Ph3P + CH2=CH2
Br
1070-3632/05/7507-1074 2005 Pleiades Publishing, Inc.

PROPERTIES OF ONIUM SALTS OF PHOSPHORUS AND NITROGEN
1075
To elucidate the mechanism of the observed reac-
tion, we have studied the reaction of an ammonium
salt, acetyltrimethylammonium bromide, with diethyl
phosphite and found that halide ions can be alkylated
with trialkyl phosphite only in the presence of at least
fourfold excess of the alkylating agent.
methyltriphenylphosphonium bromide and 1.3 g of
dimethyl phosphite was heated in 6 ml of toluene at
100 C for 8 h and then treated as described above to
obtain 1 g (96%) of methyltriphenylphosphonium
1
hydrogen phosphite. H NMR spectrum (CDCl3), ,
2
ppm (J, Hz): 2.40 d (3H, PCH3, JPH 14.0), 3.50 d
(3H, OCH3, 3JPH 12.3), 7.70 8.10 m [15H, P(C6H5)3].
Found, %: C 64.37; H 5.15; P 15.22. C20H22O3P2.
Calculated, %: C 64.52; H 5.91; P 16.67.
According to [2, 3], tertiary amines and phosphines
react with equimolar amounts of dihalides in apolar
media (ether, benzene) with exclusive formation of
monoammonium salts on account of the fact that they
are only soluble in polar media. As shown in the
present work, heating of triphenylphosphine in ether
or benzene with equimolar amount of 1,4-dichlorobut-
2-ene results in exclusive formation of a diphospho-
nium salt. The reactions of 1,4-dichlorobut-2-ene with
trimethylamine or N-methylmorpholine under the
same conditions provide the corresponding monosalts
as major products, as well as small amounts (10%) of
disalts.
Reaction of ethylenebis(triphenylphosphonium)
dibromide with dimethyl phosphite. A mixture of
2 g of ethylenebis(triphenylphosphonium) dibromide
and 1.3 g of dimethyl phosphite was heated at 100 C
for 8 h. Excess dimethyl phosphite was distilled off,
and the residue was dried to obtain 1.8 g of a material
whose treatment with aqueous NaOH to isolate 0.3 g
of triphenylphosphine oxide, mp 154 C. Mixed
sample with an authentic sample gave no melting
point depression.
Diphosphonium salts were also formed in the reac-
tions of triphenyl- and tributylphosphines with 1,2-di-
bromoethane under conditions applied for monosalt
formation.
Reaction of acetyltrimethylammonium bromide
with diethyl phosphite. A mixture of 1 g of acetyl-
trimethylammonium bromide and 1.5 g of diethyl
phosphite was refluxed in toluene for 7 h and then
treated to obtain 1 g (93%) of acetyltrimethylammo-
The resulting data suggest that the reactions si-
multaneously involve in part two reaction centers. An
alternative explanation relying on partial solubility of
monosalts in ether or benzene seems unlikely.
1
nium ethyl hydrogen phosphite. H NMR spectrum
(CDCl3), , ppm (J, Hz): 0.90 t [3H, CH3(CH2)15N+,
JHH 6.5], 1.30 m [29H, POCH2CH3, CH3(CH2)13CH2
CH2N+], 1.70 m [2H, CH3(CH2)13CH2CH2N+], 3.30 s
[9H, (CH3)3N+], 4.10 m [4H, POCH2CH3, N+CH2
(CH2)14CH3]. Found, %: C 63.92; H 11.81; P 7.11.
C21H48NO3P. Calculated, %: C 64.12; H 12.21; P
7.89.
EXPERIMENTAL
1
The H and 31P NMR spectra were obtained on a
Varian Mercuri-300 spectrometer (300 MHz) in
CDCl3 and CD3OD.
Reaction of triphenylphosphine with 1,4-dichlo-
robut-2-ene. 1,4-Dichlorobut-2-ene, 3.5 g, was added
dropwise to 7.3 g of triphenylphosphine in dry
benzene, and the reaction mixture was refluxed on a
water bath for 16 h. The precipitate that formed was
filtered off, washed with two portions of dry ether,
and dried to obtain 8.2 g (93%) of but-2-ene-1,4-di-
ylbis(triphenylphosphonium) dichloride. 1H NMR
spectrum (CD3OD), , ppm (J, Hz): 4.20 d.d (4H,
Reaction of (1-butoxyvinyl)triphenylphospho-
nium bromide with dimethyl phosphite. A mixture
of (1-butoxyvinyl)triphenylphosphonium bromide and
2 g of dimethyl phosphite was heated in 7 ml of
toluene at 100 C for 10 h. The solvent was then re-
moved by distillation, and the residue was thoroughly
washed with dry ether and dried in a vacuum to obtain
2 g (98%) of (1-butoxyvinyl)triphenylphosphonium
methyl hydrogen phosphite. 1H NMR spectrum
(CD3OD), , ppm (J, Hz): 0.90 t [3H, O(CH2)3CH3,
JHH 6.2], 1.25 m [2H, O(CH2)2CH2CH3], 1.70 m (2H,
2
PCH2, JPH 14.5, JHH 6.5), 5.90 t (2H, CH=CH, JHH
6.9), 7.80 7.90 m (30H, PC6H5). 31P NMR spectrum
(CD3OD), P, ppm: 24.64. Found Cl , %: 10.90.
C40H36Cl2P2. Calculated Cl , %: 10.94.
3
OCH2CH2CH2CH3), 3.70 d (3H, POCH3, JPH 12.3),
4.05 t (2H, OCH2, JHH 6.2), 5.00 d.d (Hb, PCCHaHb ,
Reaction of N-methylmorpholine with 1,4-di-
chlorobut-2-ene. 1,4-Dichlorobut-2-ene, 20.2 g, was
added dropwise to 16.2 g of N-methylmorpholine in
dry ether, and the reaction mixture was left to stand
at room temperature for 7 days. The precipitate was
then filtered off, washed with dry ether, and dried to
obtain 27.5 g of a mixture of salts, whose recrystalliza-
tion from isopropanol gave 5.5 g (11%) of but-2-ene-
3
3JPH 14.3, JHH 4.5), 5.80 d.d (Ha, PCCHaHb, JPH
39.0, JHH 4.5), 7.60 7.90 m [15H, P(C6H5)3]. Found,
%: C 65.56; H 6.35; P 13.13. C25H30O4P2. Calculated,
%: C 65.79; H 6.58; P 13.59.
Reaction of methyltriphenylphosphonium bro-
mide with dimethyl phosphite. A mixture of 1 g of
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 75 No. 7 2005

1076
OVAKIMYAN et al.
1,4-diylbis(N-methylmorpholinium) dichloride. 1H
NMR spectrum (CD3OD), , ppm (J, Hz): 3.20 s [6H,
(CH3)2N], 3.50 m [8H, N(CH2CH2)2], 4.00 m [8H,
O(CH2CH2)2] , 4.25 d (4H, NCH2, JHH 6.9), 6.50 t
(2H, CH=CH, JHH 6.9). Found Cl , %: 21.25.
C14H28Cl2N2O2. Calculated Cl , %: 21.71.
to obtain 6.2 g of a mixture of salts, whose recrystal-
lization from ethyl acetate ethanol gave 3.1 g (37%)
of ethylenebis(triphenylphosphonium) dibromide, mp
1
196 C. H NMR spectrum (DMSO), , ppm (J, Hz):
2
4.20 d (4H, P+CH2CH2P+, JPH 5.5), 7.80 7.90 m
{30H, [(C6H5)3P]2}. Found Br , %: 22.10. C38H34
Br2P2. Calculated Br , %: 22.47.
The filtrate was evaporated to obtain 22 g of a mix-
ture of but-2-ene-1,4-diylbis(N-methylmorpholinium)
dichloride and 1-(N-methylmorpholinio)-4-chlorobut-
Reaction of tributylphosphine with 1,2-dibro-
moethane. A mixture of 5.3 g of tributylphosphine
and 4.9 g of 1,2-dibromoethane in toluene was heated
under argon on a water bath for 2 days. The solvent
was then removed, and the residue was thoroughly
washed with dry ether to obtain 8.8 g of a mixture of
(2-bromoethyl)tributylphosphonium bromide and
ethylenebis(tributylphosphonium) dibromide (4:1, 1H
NMR data). The mixture was recrystallized from
ether ethyl acetate to isolate 1 g of ethylenebis(tri-
butylphosphonium) dibromide. 1H NMR spectrum
(CDCl3), , ppm (J, Hz): 0.90 1.00 m {18H,
[P+(CH2(CH2)2CH3)3]2}, 1.40 1.60 m {24H,
[P+(CH2(CH2)2CH3)3]2}, 2.50 2.60 m {12H,
[P+(CH2(CH2)2CH3)3]2}, 3.30 d (4H, P+CH2CH2P+,
2JPH 6.3). Found Br , %: 26.60. C26H58Br2P2. Cal-
culated Br , %: 27.03.
1
2-enyl chloride (1:14). H NMR spectrum of 1-(N-
methylmorpholinio)-4-chlorobut-2-enyl chloride,
,
ppm: 3.10 and 3.15 s (3H, CH3N+), 3.50 m (4H,
N+CH2CH2), 4.00 m (6H, N+CH2CH2, CH2Cl),
4.15 m (2H, N+CH2), 5.80 6.40 m (2H, cis- and
trans-CH=CH).
Reaction of trimethylamine with 1,4-dichloro-
but-2-ene. 1,4-Dichlorobut-2-ene, 11.5 g, was added
with cooling to a solution of 5.4 g of trimethylamine
in dry ether, and the reaction mixture was left to stand
for 3 days. The precipitate was filtered off, thoroughly
dried with ether, and dried to obtain 11.1 g of a mix-
ture of (4-chlorobut-2-enyl)trimethylammonium chlo-
ride and but-2-ene-1,4-diylbis(trimethylammonium)
1
1
dichloride (5:1, H NMR data). H NMR spectrum
(CD3OD), , ppm (J, Hz): monosalt: 3.10 s and 3.20 s
[9H, (CH3)3N+], 3.95 m (2H, CH2Cl), 4.10 m (2H,
NCH2), 5.95 6.40 m (2H, cis- and trans-CH=CH);
disalt: 3.05 s and 3.15 s {18H, cis- and trans-
[(CH3)3N+]2}, 4.15 and 4.30 m [4H, cis- and trans-
(N+CH2)2], 6.40 m (2H, cis- and trans-CH=CH).
REFERENCES
1. Torgomyan, A.M., Ovakimyan, M.Zh., and Indzhi-
kyan, M.G., Arm. Khim. Zh., 1977, vol. 30, no. 5,
p. 439.
2. Babayan, A.T., Indzhikyan, M.G., and Gegelyan, Zh.G.,
Reaction of triphenylphosphine with 1,2-dibro-
moethane. A mixture of 6 g of triphenylphosphine
and 4.4 g of 1,2-dibromoethane was refluxed in to-
luene for 7 days. The solvent was then distilled off,
and the residue was thoroughly washed with dry ether
Zh. Org. Khim., 1966, vol. 2, no. 12, p. 2117.
3. Babayan, A.T., Martirosyan, G.T., Gyul’nazaryan, A.H.,
and Arakelyan, N.M., Arm. Khim. Zh., 1972, vol. 25,
no. 2, p. 123.
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