Synthesis of diaminophosphonium salts [Ph2(ArNH) 2P]+Br- (Ar = o-MeC6H4, p-MeC6H4, p-PriC6H4, p-EtO2CC6H4</

Article abstract of DOI:10.1080/10426500802116073

The behavior of different anilines H₂NC₆H ₄R (R = o-Me, p-Me, o-, m- and p-ⁱPr, p-OMe, p-CO ₂Et) and 2,6-Me₂C₆H₃NH₂ towards trihalophosphoranes was studied.

Full text of DOI:10.1080/10426500802116073

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Synthesis of
Diaminophosphonium Salts
[Ph2(ArNH)2P]+Br- (Ar = o-
MeC6H4, p-MeC6H4, p-Pr i C6H4,
p-EtO2CC6H4, p-MeOC6H4)
O. V. Gusev a , N. A. Ustynyuk a , T. A. Peganova a ,
A. V. Gonchar a , P. V. Petrovskii a & K. A. Lyssenko a
a A. N. Nesmeyanov Institute of Organoelement
Compounds of the Russian Academy of Sciences ,
Moscow, Russian Federation
Published online: 04 Feb 2009.
To cite this article: O. V. Gusev , N. A. Ustynyuk , T. A. Peganova , A. V. Gonchar ,
P. V. Petrovskii & K. A. Lyssenko (2009) Synthesis of Diaminophosphonium Salts
[Ph2(ArNH)2P]+Br- (Ar = o-MeC6H4, p-MeC6H4, p-Pr i C6H4, p-EtO2CC6H4, p-MeOC6H4),
Phosphorus, Sulfur, and Silicon and the Related Elements, 184:2, 322-331, DOI:
10.1080/10426500802116073
To link to this article: http://dx.doi.org/10.1080/10426500802116073
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Phosphorus, Sulfur, and Silicon, 184:322–331, 2009
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500802116073
Synthesis of Diaminophosphonium Salts
[Ph2(ArNH)2P]+Br− (Ar = o-MeC6H4, p-MeC6H4, p-PriC6H4,
p-EtO2CC6H4, p-MeOC6H4)
O. V. Gusev, T. A. Peganova, A. V. Gonchar, P. V. Petrovskii,
K. A. Lyssenko, and N. A. Ustynyuk
A. N. Nesmeyanov Institute of Organoelement Compounds of the
Russian Academy of Sciences, Moscow, Russian Federation
i
The behavior of different anilines H NC H R (R = o-Me, p-Me, o-, m- and p− Pr, p-
2
6
4
OMe, p-CO Et) and 2,6-Me C H NH towards trihalophosphoranes was studied.
2
2
6
3
2
2,6-Me C H NH failed to form the diaminophosphonium salt [Ph P{NH(2,6-
2
6
3
2
2
Me C H )} ]Br, and the aminophosphine oxide Ph (2,6-Me C H NH)PO was the
2
6
3
2
2
2
6
3
only isolated product. Both o- and p-toluidine gave the corresponding diaminophos-
phonium salts; however in the case of o-toluidine, the yield was low and a mix-
ture with the respective aminophosphine oxide was observed. Anilines containing
methoxy and ethoxycarbonyl groups in para-position form the diaminophospho-
nium salts in reasonable yields.
Keywords Anilines; diaminophosphonium salts; 1H, 31P NMR spectra; X-ray structure
INTRODUCTION
–
Diaminophosphonium salts [R2P(NHRꢀ)2]+X are convenient start-
ing materials for synthesis of chelate complexes [M]{(NRꢀ)2PR2}.1–3
In recent years, the latter have attracted considerable attention as
potential catalysts. Although the first representatives of these com-
pounds were synthesized in 1970s, there is still no systematic study
of this class of substances. Two reviews dedicated to phosphazane and
phosphazene complexes4 and to metallated phosphonium ylides5 have
been published, which consider only partly the problems of synthesis
of aminoiminophosphoranate complexes and their organophosphorus
precursors. A new impetus to the investigation of these compounds
Received 24 March 2008; accepted 8 April 2008.
The authors are thankful to Exxon Mobil Chemical Company for financial support.
Address correspondence to N. A. Ustynyuk, A. N. Nesmeyanov Institute of Organoele-
ment Compounds of the Russian Academy of Sciences, Vavilov St. 28, 119991, Moscow,
Russian Federation. E-mail: ustynyuk@ineos.ac.ru
322

Synthesis of Diaminophosphonium Salts
323
has been given by reports on the activity of aminoiminophospho-
ranate complexes in a series of catalytic processes.3,6–9 A further
development of this field is essentially restricted by the low acces-
–
sibility of diaminophosphonium salts [R2P(NHRꢀ)2]+X as the most
general precursors of aminoiminophosphoranate complexes. The main
synthetic routes to these salts include aminolysis/chloroaminolysis of
dialkylchlorophosphines or tetraalkyldiphosphines,10,11 interaction of
tetraalkyl- or tetraphenyldiphosphines with carbon tetrachloride in
the presence of primary amines,12 quaternization of diaminophos-
phines by alkyl halides,1,13 and in situ generation of trihalophos-
phoranes followed by the reaction with primary alkyl amines.14,15
The latter approach, developed by Cristau and Garcia,14 seems to
be the most efficient and most often used. To expand the set of di-
aminodiphenylphosphonium salts, we applied the Cristau reaction
to some substituted anilines and the results obtained are presented
here.
RESULTS AND DISCUSSION
As mentioned above, diphenyl bis(phenylamino) phosphonium bromide
–
[Ph2P(NHPh)2]+Br (1) was prepared by Cristau and Garcia14 from
aniline according to Scheme 1; substituted anilines were practically
not used in these reactions, however.
We studied the reaction shown in Scheme 1 with some substituted
anilines and found that the nature and position of the substituent
exert considerable influence on the reaction outcome. The reaction of
2,6-dimethylaniline with Ph2PClBr2 did not yield the diaminophospho-
nium salt [Ph2(2,6-Me2C6H3NH)2P]+Br− (2) even after prolonged re-
fluxing in methylene chloride; instead, the new aminophosphine oxide
3 was isolated and characterized by elemental analysis and spectro-
scopic data (31P NMR: a singlet at δ = 20.8; 1H NMR: δ = 2.26 and 6.93
(2,6-Me2C6H3); δ = 7.39, 7.48, and 7.81, Ph, corresponding to two aryl
moieties in the ratio of 1:2). Presumably, the bulkiness of two o-methyl
groups forces the reaction to stop at the step of the monosubstituted
NHPh
Ph2PCl + Br2
Ph2+P
PhNH2
Ph2PClBr2
Br-
CH2Cl2, 0oC
NHPh
1
SCHEME 1

324
O. V. Gusev et al.
NH2
Me
Me
Hal
H2O
O
Ph2PClBr2
P
Me
P
Me
N
NH
Me
Me
3
4
Hal = Cl, Br
SCHEME 2
product [Ph2(2,6-Me2C6H3N=)PHal] (4); its hydrolysis during workup
gives 3 as the only isolable product (Scheme 2).
The less bulky o-toluidine in this reaction afforded a mixture of the
phosphonium salt [Ph2(2-MeC6H4NH)2P]+Br− (5) and the aminophos-
phine oxide Ph2(2-MeC6H4NH)PO (6) (Scheme 3).
Analytically pure 5 was obtained by fractional crystallization from
isopropyl alcohol; however, the yields did not exceed 20–25 %. The
phosphorus resonance in 5 (δ = 30.4) is similar to that reported for 1;14
the singlet at δ = 2.29 in the 1H NMR spectrum of 5 corresponds to the
methyl groups and indicates free rotation of the 2-MeC6H4NH moiety.
The signals of the hydrogen atoms of the phenyl rings have chemical
shifts and coupling constants typical for compounds of this type.
The molecular geometry of the diaminophosphonium salt 5 was
determined by X-ray crystallography (Figures 1 and 2). The phos-
phorus atom in 5 has a distorted tetrahedral configuration with the
N(1)P(1)N(2) angle increased to 119.6(1) degrees. The nitrogen atoms
are essentially flattened, the sums of the bond angles are 359.1 degrees
NH2
Me
Me
NH
NH
O
+
P
Br-
Ph2PClBr2
+
P
Me
NH
Me
5
6
SCHEME 3

Synthesis of Diaminophosphonium Salts
325
FIGURE 1 ORTEP plot of the diaminophosphonium cation in 5. Thermal
ellipsoids are drawn at 50% probability level. Selected bond lengths (Å):
P(1)-N(1) 1.625(2), P(1)-N(2) 1.633(2), P(1)-C(15) 1.793(2), P(1)-C(21) 1.796(2),
N(1)-C(1) 1.434(3), N(2)-C(8) 1.441(3), and bond angles (◦): N(1)-P(1)-N(2)
119.64(11), N(1)-P(1)-C(15) 107.37(11), N(2)-P(1)-C(15) 107.03(11), N(1)-P(1)-
C(21) 106.30(11), N(2)-P(1)-C(21) 106.92(11), C(15)-P(1)-C(21) 109.32(10), C(1)-
N(1)-P(1) 126.96(18), C(8)-N(2)-P(1) 127.76 (17).
and 357.8 degrees for N(1) and N(2), respectively. It should be noted
that the bond P(1)–N(2), 1.633(2)Å, is slightly elongated compared to
the bond P(1)–N(1), 1.625(1) Å. Such differences in the configuration of
the nitrogen atoms can be caused by intermolecular hydrogen bonding.
Indeed, the phosphonium cations in the crystal are assembled to infi-
nite chains along the crystallographic b axis by rather short N-H. . . Br
bonds with similar N. . . Br distances of 3.418(3) Å and 3.356(3) Å for
N(1) and N(2), respectively (Figure 2).
Using the geometry of 5 obtained by X-ray diffraction as the starting
point, we have performed DFT calculations (PBE/TZ2p) of the cation
[Ph2(2,6-Me2C6H3NH)2P]+using the PRIRODA program package.[16]

326
O. V. Gusev et al.
FIGURE 2 The N-H. . . Br bonded chains in the crystal of 5. The parameters
for the hydrogen bonds are N(1). . . Br(1) 3.431(1) Å, H(1N). . . Br(1) 2.51 Å,
N(1)-H(1N)-Br(1) 157◦; N(2). . . Br(1) 3.358(1) Å, H(2N). . . Br(1) 2.54 Å, N(2)-
H(2N)-Br(1) 168◦.
The optimization of the cation geometry revealed that although the
presence of the methyl groups at C(6) and C(13) (Figure 1) results in
some steric repulsion between these methyl groups and the atom N(1),
the intramolecular contacts in the cation are in general within the sum
of the van-der-Waals radii. Thus according to DFT calculations, the
steric overcrowding cannot fully explain the low yields of 5 and the
impossibility of formation of 2.
The reaction of p-toluidine leads smoothly to the phosphonium salt
[Ph2(p-MeC6H4NH)2P]Br (7) in 59% yield. The phosphorus resonance
was observed at δ = 28.0, close to the corresponding resonances in 1
and 5. It is noteworthy that the corresponding chloride salt has been
recently synthesized from Ph2PCl3 and p-tolylamine.3
The presence of a bulky isopropyl group in the para-position of ani-
line also does not prevent the formation of the phosphonium salt 8,
which was obtained in 70% yield and characterized by elemental anal-
ysis and its spectroscopic data (Scheme 4).
The fact that o-substituted anilines are much less prone to form the
corresponding diaminophosphonium salts allowed us to use the more
easily available isomeric mixture of isopropyl aniline (71.5% p-, 25.6%
o-, and 2.9% m-) instead of the pure p-isomer. Although the content of
the o-isomer in this mixture is high, the formation of its phosphonium
salt is sterically unfavorable, and it is mainly consumed to bind the

Synthesis of Diaminophosphonium Salts
327
NH2
NH
+
P
Br-
Ph2PClBr2
NH
8
SCHEME 4
acid produced in the reaction. Trace amounts of the phosphonium salt
that should form from m-isopropylaniline were probably lost during the
workup procedure.
The anilines p-MeOC6H4NH2 and p-EtO2CC6H4NH2 were reacted
in the presence of triethylamine as HCl quencher. The corresponding
bis(arylamino) diphenylphosphonium salts 9 and 10 were prepared in
35–40% yields and characterized by their spectroscopic data. The 31P
NMR spectra of 9 and 10 showed a singlet at 27.4 and 27.7, respectively.
The diaminophosphonium bromides obtained are white crystalline air
stable substances.
In summary we demonstrated that the Cristau reaction is very
applicable to p-substituted anilines and gives the corresponding di-
aminophosphonium salts in reasonable yields, whereas o-substituted
anilines do not easily afford the respective diaminophosphonium salts
due to steric reasons.
EXPERIMENTAL
All reactions were carried out in dry argon atmosphere in freshly dried
and distilled CH2Cl2; isolation and purification were performed in air.
1H and 31P NMR spectra were obtained with a Bruker AMX-400 spec-
trometer, and chemical shifts are given in δ scale relative to TMS and
85% H3PO4, respectively.
Single crystal X-ray diffraction analysis of 5: (C26H26N2PBr, M =
477.37), monoclinic, space group P21/n, measurement at 120(2) K:
a = 11.731(1), b = 12.4295(10), c = 17.299(3) Å, β = 98.568(1)◦,

328
O. V. Gusev et al.
V = 2494.2(5) Å3, Z = 4 (Zꢀ=1), dcalc = 1.271 g.cm–3, µ(MoKα) = 17.26
ñm−1, F(000) = 984. Intensities of 16,781 reflections were measured
with a Bruker AXS Smart 1000 CCD (ω-scan, θ < 55.8◦), and 5927 in-
dependent reflections [Rint = 0.0416] were used in further refinement.
The refinement converged to wR2 = 0.0786 and GOOF = 0.945 for
all independent reflections (R1 = 0.0393 was calculated against F for
3808 observed reflections with I > 2σ(I)). The hydrogen atoms of the
NH groups were located from the Fourier density synthesis, while the
positions of the other hydrogen atoms were calculated geometrically.
All calculations were performed using SHELXTL PLUS 5.0. The crys-
tallographic data for 5 have been deposited with the Cambridge Crys-
tallographic Data Center, CCDC 623570. Copies of this information
may be obtained free of charge from: The Director, CCDC, 12 Union
Road, Cambridge, CB2 1EZ, UK (Fax: +44-1223-336033; e-mail: de-
posit@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk).
Synthesis of Ph2(2,6-Me2C6H3NH)PO (3)
A solution of Br2 (4.0 g, 1.26 mL, 25 mmol) in CH2Cl2(10 mL) was
added dropwise to a solution of chlorodiphenylphosphine (5.5 g, 4.5
mL, 25 mmol) in CH2Cl2(25 mL) during 30 min. Then a solution of
2,6-dimethylaniline (12.1 g, 12.5 mL, 100 mmol) in CH2Cl2(100 mL)
was added dropwise at 0◦C during 1 h. The mixture was refluxed for
144 h with vigorous stirring. The solvent was evaporated in vacuum
and the residue was recrystallized from ethanol (30 mL) to give white
crystals of 3. Yield: 3.77 g (47 %). M.p. 219◦C. Calcd for C20H20NPO: C,
74.75; H, 6.27; N, 4.36 %. Found: C, 74.57; H, 6.31; N, 4.44 %. 1H NMR
(CDCl3): δ = 2.26 (s, 6H, Me); 4.66 (m, 1H, NH); 6.93 (m, 3H, m-H, p-H,
C6H3Me2); 7.39 (m, 4H, m−H, Ph); 7.48 (t, J = 3.6 Hz, 2H, p-H, Ph); 7.81
(dd, J = 3.8 Hz, JPH = 3.0 Hz, 4H, o-H, Ph). 31P NMR (CDCl3): δ = 20.8.
Synthesis of [Ph2(o-MeC6H4NH)2P]Br (5)
A solution of Br2 (8.0 g, 2.53 mL, 50 mmol) in CH2Cl2(30 mL) was added
dropwise to a solution of chlorodiphenylphosphine (11.0 g, 9.0 mL, 50
mmol) in CH2Cl2(50 mL) during 40 min. Then a solution of o-toluidine
(21.4 g, 21.4 mL, 200 mmol) in CH2Cl2(30 mL) was added dropwise at
0◦C during 2 h. The mixture was warmed up to 20◦C and stirred for
72 h. The solvent was evaporated in vacuum. 31P NMR spectra of the
residue in CD3OD showed two main signals at 30.4 (the bromide 5) and
22.4 (the oxide 6) with an integral ratio of 1:2. The residue was washed
with benzene (3 × 30 mL) to remove the largest part of the oxide 6 and

Synthesis of Diaminophosphonium Salts
329
recrystallized twice from PriOH (25 mL) to afford 5.49 g of 5 (23 %).
M.p. 243 ◦C. Calcd for C26H26BrN2P: C, 65.41; H, 5.49; N, 5.87 %. Found
C, 65.79; H, 5.78; N, 5.85 %. 1H NMR (CDCl3): δ = 2.29 (s, 6H, Me); 6.9–
7.1 (m, 8H, C6H4Me); 7.49 (m, 4H, m-H, Ph); 7.67 (m, 2H, p-H, Ph); 7.76
(dd, J = 3.6 Hz, JPH = 3.0 Hz, 4H, o-H, Ph); 8.59 (m, 2H, NH). 31P NMR
(CD3OD): δ = 30.4; (CDCl3): δ = 35.2.
Synthesis of [Ph2(p-MeC6H4NH)2P]Br (7)
A solution of Br2 (8.0 g, 2.53 mL, 50 mmol) in CH2Cl2(30 mL) was
added to a solution of chlorodiphenylphosphine (11.0 g, 9.0 mL, 50
mmol) in CH2Cl2(50 mL) during 40 min. Then a solution of p-toluidine
(21.4 g, 21.4 mL, 200 mmol) in CH2Cl2(30 mL) was added dropwise
◦
at 0◦C during 2 h. The mixture was warmed up to 20 C and stirred
effectively for 24 h. The solvent was evaporated in vacuum, and the
residue was washed with benzene (3 × 30 mL), water (3 × 20 mL) and
recrystallized from ethanol (30 mL). Yield: 14.08 g (59%). M.p. 210 ◦C.
Calcd for C26H26BrN2P: C, 65.41; H, 5.49; N, 5.87%. Found C, 65.72;
H, 5.48; N, 5.80 %. 1H NMR (CDCl3): δ = 2.09 (s, 6H, Me); 6.75 (d, J =
10.4 Hz, 4H, C6H4Me); 7.29 (d, J = 10.4 Hz, 4H, C6H4Me,); 7.39 (m, 4H,
m-H, Ph); 7.52 (m, 2H, p-H, Ph); 8.09 (dd, J = 7.4 Hz, JPH = 13.5 Hz,
4H, o-H, Ph); 9.26 (d, J = 18.0 Hz, 2H, NH). 31P NMR (CDCl3): δ = 28.0.
Synthesis of [Ph2P(p-PriC6H4NH)2]Br (8)
Method A
A solution of Br2 (8.0 g, 2.53 mL, 50 mmol) in CH2Cl2(30 mL)
was added to a solution of chlorodiphenylphosphine (11.0 g, 9.0 mL,
50 mmol) in CH2Cl2(50 mL) during 40 min. Then a solution of p-
isopropylaniline (27.0 g, 27 mL, 200 mmol) in CH2Cl2(30 mL) was
added dropwise at 0◦C for 2 h. The mixture was allowed to warm to
room temperature and was stirred for 24 h. The solvent was evap-
orated in vacuum and the residue was washed with benzene (3 × 50
mL), water (3 × 30 mL) and recrystallized from ethanol (20 mL) to yield
◦
18.73 g of 8 (70%). M.p. 230 C. Calcd for C30H34BrN2P: C, 67.54; H,
6.42; N, 5.25 %. Found C, 67.68; H, 6.42; N, 5.31 %. 1H NMR (CD3OD):
δ = 1.38 (d, J = 7.0 Hz, 12H, CHMe2); 3.04 (septet, J = 7.0 Hz, 2H,
CHMe2); 7.34 (m, 8H, C6H4Pri); 7.86 (m, 4H, m-H, Ph); 7.97 (m, 2H,
p-H, Ph); 8.17 (m, 4H, o-H, Ph). 31P NMR (CD3OD): δ = 26.6.
Method B
Analogously 18.19 g (68%) of [Ph2(p-PriC6H4NH)2P]Br (8) was ob-
tained using the isomeric mixture of o-, m−, and p-isopropylaniline

330
O. V. Gusev et al.
(27.0 g, 27 mL, 200 mmol) instead of the same amount of pure p-
isopropylaniline.
Synthesis of [Ph2(p-MeOC6H4NH)2P]Br (9)
A solution of Br2 (4.0 g, 1.3 mL, 25 mmol) in CH2Cl2(10 mL) was added
to a solution of chlorodiphenylphosphine (5.5 g, 4.5 mL, 25 mmol) in
dry CH2Cl2(25 mL) during 40 min. Then a solution of p-anizidine (6.15
g, 50 mmol) and NEt3 (5.1 g, 7 mL, 50 mmol) in CH2Cl2(20 mL) was
added dropwise at 0◦C during 1 h. The mixture was warmed up to 20◦C
and stirred for 24 h. The solvent was evaporated in vacuum, and the
residue was washed with benzene (3 × 20 mL), acetone (2 × 10 mL)
and recrystallized from ethanol (30 mL). Yield: 3.39 g (39 %). M.p. 187
◦C. Calcd for C26H26BrN2O2P: C, 61.31; H, 5.14; N, 5.50 %. Found C,
61.17; H, 5.17; N, 5.44 %. 1H NMR (CD3OD): δ = 3.92 (s, 6H, Me); 4.82
(broad s, 2H, NH); 7.05 (d, J = 8.8 Hz, 4H, C6H4OMe); 7.34 (d, J = 8.8
Hz, 4H, C6H4OMe); 7.8–7.9 (m, 4H, m-H, Ph); 7.98 (t, J = 7.5 Hz, 2H,
p-H, Ph), 8.15 (dd, J = 8.1 Hz, JPH = 13.6 Hz, 4H, o-H, Ph).31P NMR
(CD3OD): δ = 27.4.
Synthesis of [Ph2(p-EtO2CC6H4NH)2P]Br (10)
The synthesis was carried out in analogy to that of 9 using p-
NH2C6H4CO2Et (8.25 g, 50 mmol) instead of p-anizidine. The reaction
mixture was stirred for 20 h. The solvent was evaporated in vacuum,
the residue was washed with benzene (3 × 10 mL), water (2 × 10 mL)
and recrystallized from ethanol (50 mL). Yield: 5.13 g (35 %). Calcd for
C30H30BrN2O4P: C, 60.72; H, 5.10; N, 4.72 %. Found C, 60.78; H, 5.04;
1
N, 4.77 %. H NMR (CD3OD): δ = 1.52 (t, J = 7.2 Hz, 6H, CH2Me);
4.50 (q, J = 7.2 Hz, 4H, CH2Me); 7.50 (d, J = 8.7 Hz, 4H, C6H4CO2Et);
7.88 (m, 4H, m-H, Ph); 8.04 (m, 2H, p-H, Ph); 8.11 (d, J = 8.7 Hz, 4H,
C6H4CO2Et), 8.25 (dd, J = 7.5, JPH = 13.8 Hz, 4H, o-H, Ph). 31P NMR
(CD3OD): δ = 27.7.
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Synthesis of Diaminophosphonium Salts
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