Synthesis of metal complexes of polyalkylene(arylene) phosphorous amides

Article abstract of DOI:10.1134/S1070363208070074

Reactions of phosphorous triamides with symmetrical diols in equimolar ratio were studied. These reactions result in formation of unique poly(oligo)amidophosphorous systems. The products obtained are used as ligands for the synthesis of metal complexes of a new type.

Full text of DOI:10.1134/S1070363208070074

ISSN 1070-3632, Russian Journal of General Chemistry, 2008, Vol. 78, No. 7, pp. 1334–1337. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © A.T. Teleshev, Van Te, V.Yu. Mishina, I.V. Abrashina, E.E. Nifant’ev, 2008, published in Zhurnal Obshchei Khimii, 2008, Vol. 78,
No. 7, pp. 1097–1100.
Synthesis of Metal Complexes
of Polyalkylene(arylene) Phosphorous Amides
A. T. Teleshev, Van Te, V. Yu. Mishina, I. V. Abrashina, and E. E. Nifant’ev
Moscow Pedagogical State University,
Nesvizhskii per. 3, Moscow, 119021 Russia
е-mail: chemdept@mtu-net.ru
Received November 9, 2007
Abstract—Reactions of phosphorous triamides with symmetrical diols in equimolar ratio were studied. These
reactions result in formation of unique poly(oligo)amidophosphorous systems. The products obtained are used
as ligands for the synthesis of metal complexes of a new type.
DOI: 10.1134/S1070363208070074
1
:1
Ρ−ΟRΟ
By now there has been much basic research on the
chemistry of high-molecular compounds containing
various P(V) functions [1–4]. At the same time, the
works on analogous P(III) derivatives are few in
number and often mutually contradictory [5–11]. It is
significant that peculiar features inherent in
compounds with phosphite, amidophosphite, and
phosphonite groups have, as a rule, not been revealed.
nP(NR' ) + nHO−R−OH
+ 2nHNR2'
2
3
NR2'
n
This reaction was carried out in dioxane under
argon. The amine liberated in the reaction was
gradually removed from the reaction medium. The
process was monitored by a combination of TLC and
3
1
Р NMR. After the reaction was complete, the solvent
and residual amine were removed from the reaction
flask. The process was performed by two alternative
procedures. The first involved complete removal of
volatile substances in a vacuum and afforded the target
product partially modified by cross-linked molecules
Taking above into account, we focused on the
synthesis of polyamidophosphite systems by the
reaction of phosphorous triamides with glycols or
diatomic phenols in an equimolar ratio. We considered
this synthesis as the first part of a project devoted to
the design and study of the catalytic properties of
unique high-molecular systems. We expected to obtain
substances combining features inherent in catalysts of
different types. Actually, these compounds, being
organosoluble metal complexes, could behave as
known homogeneous catalysts. On the other hand,
three-dimensional and cross-linked objects could prove
organoinsoluble and corresponding to heterogeneous
catalysts.
(
form А). This form is represented by elastic granules
no longer capable of dissolution. The second procedure
involved mild distillation of the main part of volatile
products in a vacuum and provides a soluble substance
form В). The product thus could be studied by
NMR: Its chemical shift was 147 ppm, which cor-
responds to phosphorous amidodiesters.
3
1
(
Р
The reaction is general in nature and can be carried
out with both hexamethylphosphorous triamide and its
ethyl homolog. Of aliphatic diols, hexamethylene-1,6-
diol and decamethylene-1,10-diol were involved in the
reaction and of aromatic diols, hydroquinone, 1,4-
dihydroxydiphenyl and 2,2-bis(4-hydroxyphenyl)pro-
pane (DIAN).
The first step of this work, which involved
phosphorylation, showed that this process holds
promise.
0oC
dioxane
Ρ−Ο(CH ) Ο
2 6
8
Ρ−Ο(CH ) Ο
2
6
(
NEt ) P + HO(CH ) OH
+
+ HNEt2
2
3
2 6
NEt2
Ο(CH ) Ο
2 6
n
n'
1334

SYNTHESIS OF METAL COMPLEXES
1335
To characterize the resulting products, we studied
their relative thermooxidative stability. The objects for
study were samples A and B with the following
principal structural fragments:
To verify the assignment the exo effects on the
thermal decomposition of linear (B) and cross-linked
(A) oligomers, we prepared their calibration mixture
obtained from hexane-1,6-diol and hexamethylphos-
31
phorous triamiide in a 1.2:1.0 molar ratio. The
P
Ρ−Ο(CH ) Ο
Ρ−Ο(CH ) Ο
2 6
2
6
NMR spectrum of the calibration mixture contained
expected signals at 147 and 139 ppm with an intensity
ratio of 1.2:1. The DTA curve of this sample showed
exo effects in the corresponding ranges: 250–300°С
and 300–340°С.
Ο(CH ) Ο
NEt2
2
6
n
A
B
The DTA curve of oligophosphite B initially shows
a weak endothermic effect in the range 130–155°С
with a slight weight loss due to liberation of residual
volatile substances. Further heating leads to a well-
defined exothermic effect in the range 280–315°С with
a sharp weight loss which implies strong decom-
position of the polymer.
Thus, cross-linked oligomers proved to be ther-
mally more stable than linear.
Analyzing the DTA results as a whole we can note
that the polyamidophosphites and polyphosphites in
hand decompose at relatively high temperatures. This
characteristic makes these compounds useful
candidates for various technologies demanding highly
thermally stable polymers.
The DTA curve of oligophosphite A shows initia-
tion of a strong thermal decomposition in the
temperature range 260–320°С; the observed effect is
associated with the heat release attendant in the
decomposition of a linear oligomer admixture.
However, the observation of a peak in this temperature
range can also attest continuation of chemical reactions
in the solid bulk of the oligomer, such as, first, further
disproportionation to form triester fragments (cross-
linking of the polymer) is possible and, second,
reactions involving the amido groups, specifically P–N
bond cleavage with Р–ОН bond formation.
The second part of this investigation involved
reactivity assessment of the obtained compounds in the
B form. We found that these compounds are can be
easily oxidized with di-tert-butyl peroxide and can
take up sulfur.
We also studied the possibility of application of the
obtained compounds as ligands for immobilized metal
complexes. Rhodium and molybdenum complexes
were synthesized.
The most vigorous exothermic destruction of
oligophosphite A with a sharp weight loss takes place
in the temperature range 320–350°С.
acacRh(CO)
m acacRh(CO)2
Ρ−Ο(CH ) Ο
2 6
Ρ−Ο(CH ) Ο
2 6
−m CO
NEt2
NEt2
m
n−m
Ρ−Ο(CH ) Ο
2
6
Mo(CO)5
NEt2
n
n Mo(CO)6
n CO
Ρ−Ο(CH ) Ο
2 6
−
NEt2
n
–
1
The ligand exchange in acetylacetonatodicarbonyl-
rhodium(I) was performed in dioxane at room
temperature using the B form (P:Ph molar ratio 3:1).
The excess of the organophosphorus oligomer does not
affect the degree of ligand exchange in acacRh(CO)2
and gives rise to a mono-substituted complex like
acacRh(CO)L. The formation of the complex is con-
firmed by the observation of a ν(CO) band at 1989 cm
in the IR spectrum and a doublet at 138.4 ppm ( J
1
PRh
248.5 Hz), characteristic of amidophosphite rhodium
3
1
complexes, in the P NMR.
It should be noted that upon complex formation
oligomer B almost loses its ability to dissolve in
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 7 2008

1
336
TELESHEV et al.
Catalytic activity of complexes асасRh(СО)L in the hydrogenation and isomerization of hept-1-ene (toluene, 70°С, РН2 1 atm,
-
3
–1
–1
[
Rh]=5×10 g-at l , [1-heptene] = 1 mol l , reaction time 100 min)
Catalytic properties
L in асасRh(СО)L
yield, %
–1
–1
α, mol Н
2
(g-at Rh ) min
heptane
20
trans-hept-2-ene cis-hept-2-ene
Oligo(hexamethylene diethylphosphoamidite)
Triethyl phosphite
0.41
0.42
0.57
35
19
21
14
10
11
21
Triphenylphosphine
29
organic solvents. Due to this property, the metal
polymer containing excess free P(III) atoms holds pro-
mise for application in catalytic reactions of carbon(II)
oxide. Such reactions, e.g., hydroformylation, require
the acacRh(CO)L–nL reaction system to contain a
buffer organic P(III) ligand nL for maintaining exis-
tence of active centers in the catalytic system [12].
Synthesis of preparing oligo(phosphoramidites)
(form B) (general procedure). To 0.01 mol of diol in
10 ml of dioxane, 0.01 mol of phosphorous triamide
was added, and the mixture was stirred at 20–45°С
(200–250 mm Hg) for 12–15 h. The solvent was then
removed by vacuum distillation (1 mm Hg) at 45°С.
31
Yield 85%. Р NMR spectrum (dioxane), δ
39.
, ppm: 147;
P
1
The immobilized metal complex of the асасRh(СО)L
type, where L is oligo(hexamethylene diethylphosphor-
amidite) was studies as a catalyst for hydrogenation of
hept-1-ene. The hydrogenation was carried out at 70°С in
toluene.
Oligo[acetylacetonatocarbonyl(hexamethylene
diethylphosphoramidite)rhodium(I)]. To 2.19 g
(0.01 mol) of oligo(hexamethylene diethylphos-
phoramidite) (form B) in 10 ml of dioxane, 0.86 g
(
0.0033 mol) of acetylacetonatodicarbonylrhodium(I)
According to the resulting data, oligo[acetyl-
acetonatocarbonyl(hexamethylene diethylphosphor-
amidite)] as a catalyst precursor offers no advantages over
rhodium complexes with trethyl phosphite or triphe-
nylphosphine ligands (see table). Note that the reaction
with the catalyst based on oligo(hexamethylene diethyl-
phosphoramidite) occurs in preference for isomerization to
trans-hept-2-ene, probably due to stereo-chemical features
of the carrier ligand (see table).
was added. The mixture was stirred at 20°С for 30 min
under argon. Precipitate formation was observed. The
solvent was removed by vacuum distillation, and the
residue was dried at 70–80°С (1 mm Hg). The product
is a solid friable light-yellow substance insoluble in
organic solvents. Decom. point 135–150°С. IR
–1 31
spectrum (КBr): ν(CO) 1989 cm . Р NMR spectrum
(
dioxane): δ 138.4 ppm. Found, %: С 45.81, 45.93; H
P
6
.37, 6.61; P 7.67, 7.94. С H NO PRh. Calculated,
1
6
28
3
Attempted additional activation of the rhodium
oligo(hexamethylene diethylphosphoramidite) complex
by treatment with molecular oxygen led to a sharp fall
of the hydrogenating activity of the system, which is
probably connected with oxidation of the oligomeric
phosphorus-containing ligand.
%: С 46.16; Н 6.78; Р 7.44.
Oligo[pentacarbonyl(hexamethylene diethylphos-
phoramidite)molybdenum(0)]. To 2.19 g (0.01 mol)
of oligo(hexamethylene diethylphosphoramidite) (form
B) in 10 ml of dioxane, 2.64 g (0.0033 mol) of hexa-
carbonylmolybdenum(0) was added. The mixture was
stirred under argon at 95°С for 2 h. The solvent was
then removed by distillation, and the residue was dried
in a vacuum at 70–80°С. The product is a solid friable
EXPERIMENTAL
31
The Р NMR spectra were registered on a Bruker
31
substance. Р NMR spectrum (dioxane): δ 164.3 ppm.
WP-80 instrument at 32.4 MHz, external reference
P
Found, %: С 47.19, 46.88; Н 6.98, 6.79; Р 8.57, 8.39.
8
5% Н РО . Thermal analysis was carried out on a
3 4
С H MoNO P. Calculated, %: С 47.37; Н 7.16; Р
Shimadzu DTG-50 instrument, accuracy 1%, sen-
15 27
2
–
1
8.14.
sitivity 0.005 mg, heating rate 20.0°C min , reference
an empty aluminum cell. The IR spectra were
registered on a Specord 75IR instrument from KBr
pellets.
Hydrogenation. The complex асасRh(СО)L,
×10 mol, was placed under argon to a reactor
–
5
5
maintained at 70°С and containing 10 ml of toluene.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 7 2008

SYNTHESIS OF METAL COMPLEXES
1337
–
2
Hept-1-ene, 10 mol, was injected to the reactor through
a membrane, and the system was purged with a dry
oxygen-free hydrogen. The reaction time was counted
from the moment when the stirrer was turned on. The
specific activity α was calculated from the volume of
consumed hydrogen. The yields of heptanes and
isomerization products was calculated from GLC data
5. Petrov, K.A., Nifant’ev, E.E., Lysenko, T.N., and
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. Nifant’ev, E.E., Markov, S.M., and Tuseev, A.P.,
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(
column 15% β,β-oxydipropionitrile on Chromosorb Р).
8
. Bross, J. and Deronet, D., Makromol. Chem., 1989,
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