A novel synthesis of alcl[(NPh)2P(O)H] and SiCl 2[(NPh)2P(O)H]: Two new phosph(V)azane derivatives

Article abstract of DOI:10.1080/10426500500366848

Reactions of phosph(V)azane derivatives of bis(anilino)phosphine oxide (PhNH)₂P(O)H (1) with AlCl₃ and SiCl₄ produce two new phosph(V)azane complexes, AlCl[(NPh)₂P(O)H] (2) and SiCl ₂[(NPh)₂

Full text of DOI:10.1080/10426500500366848

Phosphorus, Sulfur, and Silicon, 181:1675–1680, 2006
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500500366848
A Novel Synthesis of AlCl[(NPh) P(O)H] and
2
SiCl [(NPh) P(O)H]: Two New Phosph(V)azane
2
2
Derivatives
Abbas Tarassoli
Ziba Khodamoradpur
Chemistry Department, Shahid Chamran University, Ahvaz, Iran
Reactions of phosph(V)azane derivatives of bis(anilino)phosphine oxide
(
PhNH) P(O)H (1) with AlCl and SiCl produce two new phosph(V)azane
2 3 4
complexes, AlCl[(NPh) P(O)H] (2) and SiCl [(NPh) P(O)H] (3). In these reactions,
2
2
2
an HCl elimination occurs and M N bonds (M = Si, Al) form directly between
a bis(anilino)phosphine oxide ligand with aluminum and silicon halides. The
reactions do not require any base to deprotonate the phosphazane ligand. The final
products have been fully characterized by means of elemental analysis and IR, MS,
1
13 31 27
29
and multinuclear NMR ( H, C, P, Al, and Si) spectroscopy.
Keywords 27Al NMR; aluminum halides; bis(anilino)phosphine oxide; phosph(V)azane
derivatives; silicon halides
Phosphazanes that contain phosph(III)azanes and phosph(V)azanes
have attracted by far the most attention because they offer different
coordination modes involving the “hard”(N) in phosph(V)azanes and
the “soft”(P) centers in phosph(III)azanes for a generation of chelation
complexes containing different metals with a main group and transition
1
−11
metals.
Our studies, including the investigation of synthesis and the coordi-
nation chemistry of some acyclic phosph(V)azanes, led us to study the
1
2
novel ligand bis(anilino)phosphine oxide, (PhNH)2P(O)H (1). This lig-
and has been synthesized about 20 years ago, but its coordination chem-
istry as an amido phosphazane ligand has not been known and had very
little attention (Scheme 1). It bears active sites as hard and soft centers
Received April 12, 2005; accepted September 1, 2005.
Support of this work by the Shahid Chamran University, Ahvaz, Iran (project No. 217)
is gratefully acknowledged.
Address correspondence to Abbas Tarassoli, Shahid Chamran University, Chemistry
Department, College of Science, Ahvaz, Iran. E-mail: tarassoli a@cua.ac.ir
1675

1
676
A. Tarassoli and Z. Khodamoradpur
N, O, and P, and is very reactive to form various coordination complexes
with main-group and transition metals.1,5
SCHEME 1
We were interested in the investigation of its reaction with active
main group metal halides such as AlCl3 and SiCl4. Because of the
critical role of aluminum compounds in polyolefin catalysis, there has
been a growing interest in the coordination chemistry of this metal.
These systems have long been known to function as useful Lewis acid
catalysts, with applications as mediators in Friedel-Crafts and Diels-
Alder reactions, as alkylation reagents, and as initiators for cationic
polymerizations.1
,13
On the other hand, applications of silicon com-
pounds in organic synthesis, such as hydroxy protection, Peterson ole-
fination, and Wittig reactions,14 also have attracted research interest
in the synthesis and characterization of various silicon derivatives.
In coordination reactions of phosph(III)azanes and phosph(V)azanes,
an anionic form of a ligand can be produced either by using organo-
n
lithium reagents such as n-butyllithium (Bu Li) as a deprotonating
+
base, in which anions bind to Li via nitrogen (chalcogen) atoms, or by
using a base, such as triethylamine, to abstract hydrogen from a N H
1
,2
bond. In our reactions, no base was required to abstract hydrogen
from a phosph(V)azane ligand, and the reactions were performed di-
rectly to produce new phosph(V)azane complexes, AlCl[(NPh)2P(O)H]
(
2) and SiCl2[(NPh)2P(O)H] (3).
SCHEME 2

Phosphazane Derivatives
1677
RESULTS AND DISCUSSION
In the present research, at first we reexamined bis(anilino)phosphine
oxide (PhNH)2P(O)H (1) prepared according to an improved procedure
1
2
with a better yield (84%) than was previously reported (60%), which
is shown in Eq. (1).15
◦
8
0 C
PCl3 + PhNH2 + H2O −−−→ (PhNH)2P(O)H
(1)
The addition of AlCl3 to (PhNH)2P(O)H (1) in the ratio of 1:1 in dry THF
◦
at 25 C resulted in the formation of the complex AlCl[(NPh)2P(O)H] (2)
as a white powder in a 74% yield (Eq. (2)).
AlCl3 + (PhNH)2P(O)H −→ 2HCl + AlCl[(NPh)2 P(O)H]
Under similar conditions, 1 reacted with SiCl4 at 0 C to give
SiCl2[(NPh)2P(O)H] (3) in a good yield of 82% (Eq. (3)).
(2)
◦
SiCl4 + (PhNH)2P(O)H −→ 2HCl + SiCl2[(NPh)2 P(O)H]
(3)
Both reactions proceeded with the loss of 2 equiv. of HCl, and M N
bonds (M = Al and Si) were formed. They did not require a base for the
activation of the N H bonds. The products were air sensitive, and all
of the manipulations were carried out in an inert atmosphere. Multin-
3
1
1
13
27
29
uclear ( P, H, C, Al, and Si) NMR spectra indicated that 2 and 3
contained the ligand 1 bonded to Al and Si through nitrogen atoms.
3
1
P NMR spectra exhibited one doublet directly coupled to bonded-
hydrogen. Also, 31P{ H} NMR spectra showed only one singlet, which
1
confirmed the existence of one type of phosphorus and one type of prod-
1
uct. H NMR spectra of 2 and 3 showed phenyl and P–H resonances
with the appropriate relative intensities at δ 7.27–7.44 as a multiplet
and δ 6.33 as a doublet in 2 and at δ 7.26–7.44 as multiplet and δ 6.71
as a doublet in 3. Also 13C{ H} NMR spectra exhibited four signals in
the aromatic region that were consistent with a Cs symmetry of the
molecules. In the 27Al NMR spectrum of 2, one signal was detected that
1
2
9
proved the existence of just one type of aluminum center. The Si NMR
spectrum of 3 contained only one sharp singlet at 10.52 ppm indicating
the formation of a single product, with the silicon-29 resonance appear-
ing at a low field that supported the coordination number of four around
the silicon atom in 3.1
6,17
There was no indication of the presence of a NH bond in 2 and 3
1
from either H NMR or IR spectra. On the other hand, IR spectra ex-
hibited characteristic bands of Si Cl, Si N, and Al N strechings at
−1
13,18
4
76, 955, and 600 cm , respectively.
Also P O stretchings were
without variation, and we obtained no evidence for the involvement
of this bond during the course of reaction under the conditions of our

1
678
A. Tarassoli and Z. Khodamoradpur
experiments. In addition, the quantitative determination of chloride in
the products showed the existence of one equivalent chlorine in 2 and
two equivalent in 3.
In the mass spectrum of 2, a peak at m/z 257 was observed,
which was attributed to the loss of a chlorine group from the complex
AlCl[(NPh)2P(O)H] (2) as a quasi-molecular ion. The m/z values of 240
(
5
AlClN2Ph2), 205 (AlClN2Ph2), 209 (AlN2Ph2), 132 (AlN2Ph), 58 (PN2),
5 (AlN2), 47 (PO), 45 (PN), and 41 (AlN) could easily be assigned to
major peaks in the envelope in question.
Thus, the reaction of one equivalent of 1 with AlCl3 and SiCl4 pro-
ceeded with the elimination of HCl to generate the novel compounds 2
and 3, respectively. Spectroscopic data indicated that 1 coordinated on
N to Al or to Si directly without the presence of any base. We are cur-
rently exploring this procedure for a generation of similar complexes
using organo-aluminum or organo-silicon halide derivatives.
EXPERIMENTAL
All experiments were performed under nitrogen using standard
Schlenk techniques. The solvents were purified and dried as indicated:
Tetrahydrofurane was treated with KOH and freshly distilled twice
from sodium before use. Aniline was distilled from CaH2 and stored
over molecular sieves. NEt3 was distilled over MgSO4. Toluene was
distilled over sodium. Chloroform was distilled from P4O10. Phosphorus
trichloride, anhydrous aluminum trichloride, silicon tetrachloride, and
absolute ethanol were used as purchased from Merck Co. (Germany).
NMR spectra were recorded on a Bruker Avance DPX 500 MHz at an
ambient temperature. Chemical shifts were referenced to external TMS
1
13
29
for H NMR (500.13 MHz), C NMR (125.77 MHz) and Si NMR (99.35
31
MHz), H3PO4 85% for P NMR (202.45 MHz), and Al(NO3)3, 9H2O (1
2
7
M) in D2O for Al NMR (130.32 MHz) spectra. IR spectra were mea-
sured on a Bomem FTIR spectrophotometer. FAB(+) mass spectra were
recorded using a JEOL SX-102A instrument. Elemental analysis (C, H,
and N) was performed by the microanalytical service of the National
Iranian Oil Company (NIOC) Research Institute of Petroleum Industry,
Tehran, Iran.
The Preparation of (PhNH) P(O)H (1)
2
PCl3 (5 mL, 0.057 mol) in 10 mL of toluene was added slowly under
N2 to a sitirred solution of PhNH2 (26.02 mL, 0.285 mol) in 60 mL of
◦
◦
dry toluene at 0 C. The reaction mixture was warmed slowly to 25 C.
After 2 h, water (0.057 mol) in a H2O-CHCl3 solution was added slowly

Phosphazane Derivatives
1679
◦
to the mixture. Then the mixture was stirred at 80 C for another 2 h.
+
−
PhNH Cl was filtered from the hot reaction mixture. The solvent was
3
removed, and the white product was washed with cold toluene and then
◦
recrystallized from ethanol (yield 84%), m.p. 160 C.
IR (KBr): 3191 (s, NH), 3032–3092 (Ph), 2369 (m, sh, P H), 1175
P O), 749–690 (Ph) cm .
−1
(
1
◦
H NMR (25 C, (CD3)2 SO, ppm): 7.50–6.50 (m, 10 H, Ph), 8.09 (d,
2
1
JPNH = 8.92 Hz, 2H, NH), and 7.28 (d , JPH = 596 Hz, 1H, P H).
3
1
◦
1
P NMR (25 C, (CD3)2 SO, ppm): −4.07 (doublet of triplet, JPH =
2
6
12 Hz, JPNH = 9.19 Hz).
1
3
1
◦
C{ H} NMR (25 C, (CD3)2 SO, ppm): 115.9 (Cp), 118.3 (Cm), 129.4
(
Co), 146.0 (Ci).
Anal. calcd. for C12H13N2PO: C, 62.07; H, 5.64; N, 12.06%. Found: C,
2.09; H, 5.58; N, 12.02%.
6
The Synthesis of AlCl[(NPh) P(O)H] (2)
2
AlCl3(0.057 g, 0.431 mmol) was added to (PhNH)2 P(O)H (1) (0.1 g,
◦
0
.431 mmol) in 50 mL of dry THF under N2 at 25 C. Immediately, a
white insoluble solid precipitated, and the evolution of gas was noted.
After 2 h, the mixture was filtered. The white solid was washed with
THF and dried under a vacuum for 24 h to yield essentially pure 2 (yield
◦
7
8
7
7
4%), m.p. 175 C dec.
IR (KBr): 3097–3048 (Ph), 2397 (m, sh, P H), 1170 (br, P O), 849–
−1
05 (s, Ph), 600 (Al N) cm
.
1
◦
1
H NMR (25 C, D2O, ppm): 7.27–7.44 (m, 10H, Ph), 6.33 (d, JPH =
07 Hz, 1H, PH).
3
1
1
◦
31
1
P{ H} NMR (25 C, D2O, ppm): −7.29. P NMR: −7.29 (d, JPH =
02 Hz).
1
3
1
◦
C{ H} NMR (25 C, D2O, ppm): 122.88 (NPh), 129.20 (NPh), 129.96
2
(
NPh), 130.12 (d, JCNP = 7.67 Hz, NPh).
2
7
◦
Al NMR (25 C, D2O, ppm): 0.143 (s).
Anal. calcd. for C12H11N2OPClAl: C, 49.23; H, 3.76; N, 9.57%. Found:
C, 49.1; H, 3.5; N, 9.3%.
The Synthesis of SiCl [(NPh) P(O)H] (3)
2
2
SiCl4 (0.05 mL, 0.431 mmol) in 10 mL of dry toluene was added dropwise
to (PhNH)2 P(O)H (1) (0.1 g, 0.431 mmol) in 50 mL of dry THF under
◦
N2 at 0 C. Immediately, a white insoluble solid precipitated, and the
evolution of gas was noted. After 2 h, the mixture was filtered. The
white solid was washed with THF and dried under a vacuum for 24 h
◦
to yield essentially pure 3 (yield 82%), m.p. 170 C dec.

1
680
A. Tarassoli and Z. Khodamoradpur
IR (KBr): 3095–3025 (Ph), 2388 (m, sh, P H), 1188 (br, P O), 955
−1
(
Si N), 849–805 (s, Ph), 476 (Si Cl) cm .
1
◦
1
H NMR (25 C, D2O, ppm): 7.26–7.44 (m, 10H, Ph), 6.71 (d, JPH =
37 Hz, 1H, PH).
6
6
3
1
1
◦
31
1
P{ H} NMR (25 C, D2O, ppm): 3.18. P NMR: 3.11 (d, JPH =
36 Hz).
1
3
1
◦
C{ H} NMR (25 C, D2O, ppm): 124.95 (NPh), 126.00 (NPh), 129.97
2
(
NPh), 131.18 (d, JCNP = 5.03 Hz, NPh).
2
9
◦
Si NMR (25 C, D2O, ppm): 10.52 (s).
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