Synthesis and characterization of a novel phosph(V)azane-platinum(II) complex

Article abstract of DOI:10.1080/10426500802266365

The substitution reaction of bis(anilino)phosphine oxide (C6H5NH)2P(O)H (1) with trans-PtCl2(SEt2)2 yields the novel unprecedented phosph(V)azane-platinum complex cis-Pt(SEt2)2Cl[HNPhP(O)NPh(HNEt3)] (3). In this reaction, the bis(anilino)phosphine oxide u

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Synthesis and Characterization
of a Novel Phosph(V)azane-
Platinum(II) Complex
a
a
Abbas Tarassoli & Ziba Khodamoradpur
a
Chemistry Department, College of Science , Shahid
Chamran University , Ahvaz, Iran
Published online: 19 Feb 2009.
To cite this article: Abbas Tarassoli & Ziba Khodamoradpur (2009) Synthesis
and Characterization of a Novel Phosph(V)azane-Platinum(II) Complex,
Phosphorus, Sulfur, and Silicon and the Related Elements, 184:3, 712-718, DOI:
10.1080/10426500802266365
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Phosphorus, Sulfur, and Silicon, 184:712–718, 2009
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500802266365
Synthesis and Characterization of a Novel
Phosph(V)azane-Platinum(II) Complex
Abbas Tarassoli and Ziba Khodamoradpur
Chemistry Department, College of Science, Shahid Chamran University,
Ahvaz, Iran
The substitution reaction of bis(anilino)phosphine oxide (C H NH) P(O)H
6
5
2
(
1) with trans-PtCl (SEt ) yields the novel unprecedented phosph(V)azane-
2
2 2
platinum complex cis-Pt(SEt ) Cl[HNPhP(O)NPh(HNEt )] (3). In this reaction,
2
2
3
the bis(anilino)phosphine oxide undergoes P–H activation and a Pt(II)–P(V) bond
3
1
instead of Pt–N bond forms. P NMR spectra readily distinguish between the “N”
and “P” bonding modes. The reaction requires the presence of triethylamine (TEA)
as a base in order to deprotonate the phosphazane ligand and is separated as
+
−
+
Et NH Cl , whereas HTEA exists in the final product 3 and is acting as charge
3
balancing and H-bond structure directing agent. The products have been fully char-
1
13
31
acterized by means of IR; MS; UV-Vis; and H, C, and P NMR spectroscopy.
Keywords Bis(anilino)phosphine oxide; charge balancing; P-H activation; phosphazane
ligand; platinum complex
INTRODUCTION
Over the past decade, there has been a growing interest in the synthe-
sis of anionic phosph(V)azanes as anions of the p-block elements and
as their alkali-metal derivatives in view of their possible applications
in catalysis and their ability to stabilize unusual geometries at metal
1
–3
centers.
In these anionic forms of the phosph(V)azans, there are dif-
ferent coordination modes involving the “hard” (N, O) and the “soft” (S,
Se, Te) centers for generation of chelation complexes containing various
4
–9
metals with main group and transition metals.
The anionic forms
can be produced using organolithium reagents such as n-butyllithium
n
+
(
Bu Li) as a deprotonating base in which anions bind to Li via nitrogen
Received 5 April 2008; accepted 11 June 2008.
Support of this work by the Shahid Chamran University (Grant No.235-1386) is
gratefully acknowledged.
Address correspondence to Abbas Tarassoli, Chemistry Department, College of Sci-
ence, Shahid Chamran University, Ahvaz, Iran. E-mail: tarassoli@sua.ac.ir
712

Novel Phosph(V)azane-Platinum(II) Complex
713
ꢀ
or chalcogen atoms such as in the syntheses of a Pt(II) (S,S ) complex
Pt(PEt3)2[( BuN)(S)P(µ-N Bu)2P(S)(N Bu)] by Chivers et al.
t
t
t
10
Our studies, including the investigation of the synthesis and coordi-
nation chemistry of some acyclic phosph(V)azans, led us to study the
novel ligand bis(anilino)phosphine oxide, (C6H5NH)2P(O)H (1), which
1
1,12
contains both “hard” N and O coordination sites (Scheme 1).
SCHEME 1
In the present work, triethylamine is used as the deprotonating
n
base instead of Bu Li, and the ligand is converted to an unprece-
+
dented feature of type 2 in which the cation HNEt3 exists as counter
ion and in a hydrogen bond in the anion. It is notable that in the
phosph(V)azane complexes with chalcogenido substituents, the ligand
is usually coordinated through nitrogen or chalcogen. To the best of our
knowledge, the coordination through phosphorus has been explored
only in phosph(III)azanes such as the molybdenum phosph(III)azane
1
3–16
complexes.
But interestingly, herein the ligand has been attached
to platinum through a phosphorus atom in the novel compound 3; we
describe these observations in this article (Scheme 2).
SCHEME 2
RESULTS AND DISCUSSION
In the present work, bis(anilino)phosphine oxide (C6H5NH)2P(O)H (1)
is reproduced according to an improved procedure with a better yield
than that previously reported one11 as indicated in Equation (1):
◦
8
0 C
PCl3 + 2PhNH2 + H2O −→ (C6H5NH)2P(O)H + 3HCl
(1)

714
A. Tarassoli and Z. Khodamoradpur
In this reaction, the interaction of PCl3 with PhNH2 in a molar ratio
of 1:5 results in the stepwise replacement of PhNH and finally forma-
tion of (PhNH)3P, which is converted to (PhNH)2P(O)H upon addition of
H2O in a controlled hydrolysis reaction with the elimination of aniline
1
2
(
yield 84%). Then the ligand (C6H5NH)2P(O)H (1) was reacted with
trans-PtCl2(SEt2)2 in the presence of an excess of triethylamine (TEA)
to synthesize a novel complex 3 containing a Pt(II)–P(V) bond. P–H
activation occurs in the presence of TEA as the base and interestingly,
herein the ligand is finally attached to platinum(II) by phosphorus(V).
1
7
Trans-PtCl2(SEt2)2 was prepared according to the literature method.
Stirring a solution of 1 and trans-PtCl2(SEt2)2 without NEt3 resulted in
no net reaction, and the starting materials were quantitatively recov-
ered from the reaction mixture. This observation could be interpreted
based on the hard and soft acid-base principle, which states that a
hard acid prefers to react with a hard base and a soft acid prefers to
react with a soft base.18 In this complex, the phosphorus atom, which
behaves as a soft donor, is coordinated to platinum(II) as a soft Lewis
1
9
acid. Therefore, there are stronger interactions between them rather
than interaction with nitrogen or oxygen as hard atoms.
The addition of trans-PtCl2(SEt2)2 to (C6H5NH)2P(O)H in the ratio
of 1:1 in the presence of an excess of TEA affords the unprecedented
complex cis-Pt(SEt2)2Cl[HNPhP(O)NPh(HNEt3)] (3) as deep red pow-
der in 80% yield (Equation 2).
NEt3
(
C6H5NH)2 P(O)H + trans-PtCl2 (SEt2)2 −− −− −→
◦
THF, 25 C
(2)
+
−
cis−Pt(SEt )2Cl[HNPhP(O)NPH(HNEt )] + EtNH Cl
2
3
3
Multinuclear ( P, 1H, and 13C) NMR spectra indicate that
C6H5NH)2P(O)H (1) is bonded to Pt(II) through the phosphorus atom.
31
(
3
1
2
The P NMR spectrum in CDCl3 exhibits one doublet with JPNH =
95
1
0.50 Hz and with 1 Pt satellites and no coupling with a directly
3
1
1
bonded hydrogen. Also the P{ H} NMR spectrum shows only a sin-
glet that is flanked with 1 Pt satellites. The H NMR spectrum of 3
consists of two equally intense resonances at δ 1.39 and 1.43, corre-
sponding to CH3 protons in one pair of SEt2 and 2.71 and 3.25 ppm for
CH2 protons as broad multiplets in SEt2 according to a cis geometry for
SEt2 groups with the appropriate relative intensities. The methylene
protons are coupled to the CH3 protons as well as to platinum. However,
no coupling constants were measurable. There was no indication of the
95
1
1
presence of a P–H bond in 3 from either the H NMR or IR spectra.

Novel Phosph(V)azane-Platinum(II) Complex
715
The one NH group that remained intact was observed at δ 7.52 as a
2
+
doublet with JNHP = 8.58 Hz, and the presence of HTEA protons at
1
.30, 3.04, and 11.07 ppm suggests that the second NH group appeared
as the protonated HTEA cation in the product. Triethylamine was
+
1
applied to deprotonate the ligand, but based on the IR and H NMR ev-
+
idence, HTEA exists in the final product 3. It may be assumed that the
+
HTEA cation has a charge-balancing role and is acting as an H-bond
structure-directing agent. A similar situation is reported in the synthe-
sis of conventional zeolites such as phosphates and triethylammonium
2
0–22
benzene-1, 3,5-tricarboxylato (pyridine) zinc (II).
1
3
1
The C{ H} NMR spectrum of 3 contains aliphatic and aromatic
carbons with six and eight signals, respectively, which agree well
with the proposed structure 3 and are consistent with a C1 sym-
metry. On the other hand, IR results exhibit characteristic bands.
The NH stretching bonds are observed at 3407 and 3212 cm in 3,
which are assigned to HTEA and HNP, respectively. The amido NH
vibration shifted by 20 cm to a higher frequency, while the P=O
stretching showed no variation, indicating that this bond has remained
intact.
−1
+
−
1
The mass spectrum of 3 was recorded with a FAB positive source.
The mass data are easily related to the proposed structure, with the
+
normal loss of HNEt , and fragments arising from the entity and
3
the ligand. The molecular ion peak is observed at m/z 742 with a
quasi-ion peak at m/z 727, which could be attributed to loss of a
CH3 group from the complex. Other peaks are also observed at m/z
values of 526 [Pt(NHPh)P(O)NPh(HTEA)], 427 [Pt(NHPh)P(O)NPh],
4
2
10 [(SEt2)2PtCl], 375 [(SEt2)2Pt], 323 [P(O)NPh(HTEA)], 295, 275,
55, 230, 213, 195, 196, 122 (PNPh), 102 (HTEA), 93 (PhNH2), 86
(
H2CNEt2), 78, 77, 75, 66, 65, 61, 47, which could easily be assigned in
terms of the envelopes.
The electronic absorption bands for the complex 3 measured in THF
solution in the range of 200–800 nm are at 239, 510, and 546 nm.
The broad band at 239 nm is assigned to the π–π* transitions of the
phosphazane ligand. The color of this complex (deep red) is attributed
to an MLCT band.2
3–29
The electronic spectra are characterized by
two absorbances, which we suggest to be an MLCT (dπ–π*) transition,
and the π* belongs to the P=O bond. The energies of these bands
were sensitive to the nature of the solvent. In the presence of light,
a hypsochromic shift (blue shift) is observed in THF, and an increase in
the intensity of absorption in the band with higher energy (shoulder,
5
10 nm) and a decrease in the intensity of absorption in the band with
lower energy (546 nm) was observed, but in CHCl3 there were no shifts

716
A. Tarassoli and Z. Khodamoradpur
in the bands. More research is currently in progress to develop these
types of photochemistry.
It is notable that the quantitative determination of chloride in the
product and in the by-products showed the existence of one equivalent
chloride in 3. In addition, the compound had just one spot on TLC, which
indicates the existence of only one type of product. All attempts to grow
single crystals of this new complex suitable for X-ray crystallography
were unsuccessful.
CONCLUSION
The reaction of one equivalent of 1 with Pt(II) complex in the presence
+
–
of TEA results in the elimination of HCl and formation of Et3NH Cl to
generate the novel compound cis-Pt(SEt2)2Cl[HNPhP(O)NPh(HNEt3)]
(
3). The spectroscopic data indicate 2 coordinates in a “P” fashion to
the Pt(II) moiety, which is supported by hard and soft acid-base prin-
ciples and HTEA , which resides in the interlayer space and plays an
+
important role as a structural directing agent.
EXPERIMENTAL
Materials and Instrumentation
All manipulations were carried out under nitrogen using standard
Schlenk techniques. Tetrahydrofuran was treated with KOH and was
freshly distilled twice from sodium before use. Diethyl ether, hexane,
benzene, and toluene were treated with calcium chloride and distilled
over sodium after refluxing for 5 h. Chloroform was distilled from P4O10.
Aniline was distilled from CaH2 and stored over molecular sieves. NEt3
was dried over MgSO4. Phosphorus trichloride and absolute ethanol
were used as received from Merck Co.
The NMR spectra were recorded on a Bruker Avance 500 MHz at
1
13
ambient temperature. H (500.13 MHz) and C NMR (125.77 MHz)
were recorded using CDCl3 as a solvent with TMS as an external stan-
1
13
31
dard for H NMR and CDCl3 for C NMR. The P spectra (202.45
MHz) were referenced to external 85% H3PO4.
The IR spectra were measured on a Bomem FT-IR spectrophotome-
ter, and the electronic absorption spectra were obtained on a JASCO
7
850 UV-visible spectrophotometer.
The FAB(+) mass spectra were recorded using a JEOL SX-102A
instrument.

Novel Phosph(V)azane-Platinum(II) Complex
717
Synthesis of cis-Pt(SEt ) Cl [HNPhP(O)NPh(HNEt )] (3)
2
2
3
trans-PtCl2(SEt2)2 (0.192 g, 0.431 mmol) was dissolved in dry THF (10
mL) and added dropwise to a mixture of (C6H5NH)2 P(O)H (3) (0.1g,
0
.431 mmol) and NEt3 (1 mL, excess) in dry THF (50 mL) under N2 at
◦
25 C in the absence of light. Then the mixture was stirred for 3 days.
+
–
NEt3H Cl was filtered off. The solvent was removed, and a deep red
oily residue was obtained that was washed with diethyl ether. Then the
red residue was redissolved in CHCl3 and filtered. Diethyl ether was
added dropwise at 0 C to the red filtrate to precipitate a red powder
solid (yield 80%), mp 115 C dec.
◦
◦
IR (KBr): 3407 (br, HNEt3), 3212 (m, HNP), 3048 (Ph), 2975–2873
(
(
s, Et), 1451 (s, SEt2), 1257 (s, SEt2), 1193 (br, P=O), 1049, 760–692
−
1
s, Ph) cm
.
1
◦
3
H NMR (25 C, CDCl3, ppm): 1.30 (t, JHH = 7.17 Hz, 9H, HNEt3),
3
3
1
2
.39 (t, JHH = 7.45 Hz, 6H, SEt2), 1.43 (t, JHH = 6.87 Hz, 6H, SEt2),
3 3
.71 (m, JHH = 7.03 Hz, 4H, SEt2), 3.04 (quartet, JHH = 6.78 Hz, 6H,
3
HNEt3), 3.25 (m, JHH = 7.53 Hz, 4H, SEt2), 6.73–7.42 (m, 10H, Ph),
2
7
.52 (d, JPNH = 8.58 Hz, 1H, NH), 11.07 (s, br, 1H, HNEt3).
3
1
P{ H} NMR (25 C, CDCl3, ppm): −1.88 (s, JPPt = 2194 Hz). 31P
1
◦
1
2
1
NMR: −1.82 (d, JPNH = 10.50 Hz, JPPt = 2180 Hz).
1
3
1
◦
C{ H} NMR (25 C, CDCl3, ppm): 7.46 (CH3, SEt2), 8.62 (CH3,
SEt2), 12.46 (CH2, SEt2), 12.72 (CH2, SEt2), 31.83 (CH3, HNEt3), 45.93
CH2, HNEt3), 117.23 (Cp, NPh), 119.96 (Cm, NPh), 121.62 (Co, NPh),
22.62 (Ci, NPh), 128.88 (Cp, HNPh), 129.14 (Cm, HNPh), 129.31 (Co,
(
1
HNPh), 141.96 (Ci, HNPh).
UV-vis (THF, r.t.), λmax[nm]: 546, 510, 239.
MS: m/z 727, 560, 526, 426, 410, 375, 323, 295, 275, 255, 230, 213,
95, 196, 122, 102, 93, 86, 78, 77, 75, 66, 65, 61, 47.
1
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