Hydrophosphorylation of 1,3-diphenyl-2-propen-1-one and 4-phenyl-3-buten-2-one in the coordinational sphere of carbonyl complexes of Group VIB metals

Article abstract of DOI:10.1023/A:1012382918075

Synthetic procedures for preparing η² and η⁴ complexes of chalcone and henzalacetone with hexacarbonyl mononuclear complexes of Group VIB metals were developed and conditions for selective η² and η⁴-coordination

Full text of DOI:10.1023/A:1012382918075

Russian Journal of General Chemistry, Vol. 71, No. 2, 2001, pp. 191 195. Translated from Zhurnal Obshchei Khimii, Vol. 71, No. 2, 2001,
pp. 215 220.
Original Russian Text Copyright
2001 by Kuramshin, Karpenko, Cherkasov.
Hydrophosphorylation of 1,3-Diphenyl-2-propen-1-one
and 4-Phenyl-3-buten-2-one in the Coordinational Sphere
of Carbonyl Complexes of Group VIB Metals
A. I. Kuramshin, E. A. Karpenko, and R. A. Cherkasov
Kazan State University, Kazan, Tatarstan, Russia
Received November 22, 1999
2
4
Abstract Synthetic procedures for preparing
and
complexes of chalcone and benzalacetone with
2
hexacarbonyl mononuclear complexes of Group VIB metals were developed and conditions for selective
-
and 4-coordination of the heterodiene ligand were established. Hydrophosphorylation of the obtained
complexes proceeds in the coordination sphere of the metal by the Abramov reaction scheme and yields the
corresponding 2-coordinated -hydroxyphosphonates. As follows from quantum-chemical calculations,
-coordination with metals makes the heterodienes no longer planar, which explains their regioselective phos-
phorylation by the more electrophilic carbonyl group.
Inspite of the high stability of -complexes of
Group VIB metals with alkenes and arenes, as well as
the fair availability of mononuclear hexacarbonyl
complexes of these metals, usually applied for prepar-
ing complexes, there is only scarce information in
the literature concerning coordination of molecules
containing heterodiene systems like C=C C=O and
changes in the reactivity of the coordinated molecules
toward organophosphorus compounds. In detail, it has
been shown [1, 2] that enones 2-coordinated with
iron carbonyls are selectively phosphorylated by the
carbonyl group of the -enone, allowing synthesis of
-hydroxyphosphonates under conditions of kinetic
control. Group VIB metals have never been involved
in such processes.
stage photochemical substitution of carbonyl ligands
with -functional groups of heterodienes.
In the first stage, a THF solution of hexacarbonyl-
metal(0) was subjected to short (30 40 min) UV irra-
diation in the absence of unsaturated ketone with the
purpose of generation of coordinately unsaturated
metal intermediates M(CO)5 and labile pentacarbonyl
complexes M(CO)5(THF). In the second stage, they
easily reacted with -enones to form complexes of
, -unsaturated ketones. Note that a more continuous
(1 h) irradiation of the hexacarbonylmetal solution
results in substitution of a greater amount of carbonyl
ligands by THF to give mixed-ligand complexes of
the composition ( -enone)M(CO)x(THF)y. This
procedure allowed to shorten considerably the time of
synthesis of complexes I IV: The total irradiation
time in both stages of the reactions in THF solutions
was no more than 3 h against 40 h in hexane solutions
[2, 4].
Previously we reported the synthesis of adducts of
1,3-diphenyl-2-propen-1-one (chalcone) and 4-phenyl-
3-buten-2-one (benzalacetone) with hexacarbonyl
complexes of chromium subgroup metals and the re-
action of the resulting organometallic compounds with
dialkyl hydrogen phosphites by the Abramov scheme
[3]. Here we describe in more detail the results of
investigations on formation and chemical transforma-
tion of complexes of the above-mentioned unsaturated
systems with chromium, molybdenum, and tungsten
carbonyls.
Two types of complexes were obtained: 2-co-
ordinated (Ia Ic and IIa IIc) and 4-coordinated
(IIIa IIIc and IVa IVc).
Coordination induces upfield shifts of signals of
protons bound with sp2-carbon atoms (5.3 and
6.4 ppm).
In the IR spectra of compounds I IV, the C=C
Previously unknown adducts of 1,3-diphenyl-2-pro-
pen-1-one (chalcone) and 4-phenyl-3-buten-2-one
(benzalacetone) with the homoligand Group VIB
metal carbonyls Cr(CO)6, Mo(CO)6, and W(CO)6
were synthesized by our original procedure of two-
stretching vibration frequencies decrease from 1637
1
to 1530 1520 cm in chalcone and from 1645 to
1
1540 1530 cm in benzalacetone. The C=O group of
coordinated heterodienes gives two bands: a high-
1
2
frequency band at 1660 cm for
products and a
1070-3632/01/7102-0191$25.00 2001 MAIK Nauka/Interperiodica

192
KURAMSHIN et al.
process [6], the fact that the facility of the present
O
haptotropic rearrangement depends on the nature of
the complex-forming metal is explained by the
strength of the metal C=C and metal C=O bonds.
Both these bonds strengthen in the series Mo Cr W
[7], and, therefore, the ability of the corresponding
Ph CH=CH C R + M(CO)6
O
h
Ph CH=CH C R
THF
2
4
complex to the
transformation decreases.
M(CO)5
Ia Ic, IIa IIc
R
2
In terms of the aforesaid, the
complexes can be
considered as kinetically controlled products and the
4-complexes, as thermodynamically controlled pro-
ducts of the -complex formation reaction.
Ph CH=CH C
O
The reaction of excess -enone with hexacarbonyl-
metal(0) under short photochemical activation must
M(CO)4
IIIa IIIc, IVa IVc
give
2-( -enone)pentacarbonylmetal(0)
(excess
-enone inhibits haptotropic rearrangement [6]). The
reaction of -enone with hexacarbonylmetal(0) at a
stoichiometric complex:ligand ratio and under con-
tinuous irradiation of the reaction mixture (or under
thermochemical activation [8]) must result in forma-
tion of 4-( -enone)tetracarbonylmetal(0).
R = Ph (I, III); CH3 (II, IV); M = W (a), Cr (b), Mo (c).
4
low-frequency band at 1620 cm for
complexes,
belonging respectively to the free carbonyl group of
chalkone and to the carbonyl group coordinated with
tungsten. As the reaction time increases, the band at
1
1
1620 cm inreases and the band at 1660 cm de-
creases until it disappears completely. Hence, our
We performed the target synthesis of pentacarbonyl-
[
2-(1,3-diphenyl-2-propen-1-one)]tungsten(0) (Ia)
2
4
procedure allows controlling the
:
ratio by vary-
and tetracarbonyl[ 4-(1,3-diphenyl-2-propen-1-one)]-
tungsten(0) (III) under various experimental condi-
tions and isolated each of the compounds pure.
Pentacarbonyl[ 2-(1,3-diphenyl-2-propen-1-one)]-
tungsten(0) (I) was obtained by a photochemically
initiated reaction between hexacarbonyltungsten(0)
and a considerable excess of 1,3-diphenyl-2-propen-1-
one in THF.
ing the time of irradiation of the reaction mixture.
Analysis of the intensity ratio of the above two
bands led us to conclude that, at the same conditions
(reaction time and reactant concentrations), the frac-
tion of the 4-product with benzalacetone is higher
than with chalcone.
The intensity ratio of the bands at 1620 and
1
O
1660 cm in the spectra of the products of coordina-
tion of chalcone with hexacarbonylmetals decreases
in the order Mo > Cr > W. In the spectrum of the
product of the reaction of chalcone with hexacarbonyl-
molybdenum(0), a 1:1 ratio is observed, while in the
spectrum of the product of the reaction of hexacarbo-
nyltungsten(0) with chalcone, the band at 1620 cm
is practically absent.
Ph CH=CH C Ph + W(CO)6
O
h
Ph CH=CH C Ph
THF
W(CO)5
1
Ia
1
The IR spectrum of Ia displays bands at 1530 cm
2
These results suggest that the initially formed
(enone)pentacarbonylmetal(0) undergo a haptotropic
-
due to the C=C bond of chalcone, coordinated with
tungsten, and at 1660 cm due to the carbonyl group
1
rearrangement to
4-(enone)tetracarbonylmetal(0)
of 1,3-diphenyl-2-propen-1-one, not involved in co-
ordination. In the range of stretching vibrations of
carbon monoxide coordinated with transition metal
during the synthesis. The enhanced ability of coor-
dinated -enone to rearrangement in going from
chalcone to benzalacetone can be explained by in-
crease in the -electron density on the carbonyl group
in going from the methyl to phenyl derivative. Analo-
gous dependence for oxygen-containing heterodiene
systems was observed previously for iron enone com-
plexes [5]. The referees established the following
order of ability of the heterodienes to -coordination:
C(O) Ar < C(O) H < C(O) Alk. Since the first
stage of haptotropic rearrangement is a dissociative
1
(2000 1800 cm ), there are five well-resolved ab-
sorption bands at 1990, 1970, 1940, 1920, and 1900.
The upfield shift of signals of double-bond protons
(5.42 and 6.39 ppm) also confirms the fact of coor-
dination of the C=C bond of 1,3-diphenyl-2-propen-1-
one with tungsten.
Tetracarbonyl[ 4-(1,3-diphenyl-2-propen-1-one)]-
tungsten(0) (IIIa) was obtained by a thermochemi-
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 71 No. 2 2001

HYDROPHOSPHORYLATION OF 1,3-DIPHENYL-2-PROPEN-1-ONE
193
cally initiated reaction of hexacarbonyltungsten(0)
with 1,3-diphenyl-2-propen-1-one in acetonitrile at a
stoichiometric reactant ratio.
(5.37 and 6.41 ppm) is associated with the coordina-
tion of the C=C bond of 1,3-diphenyl-2-propen-1-one
with tungsten. The IR and H NMR spectra show that
no acetonitrile ligand is present in the coordination
sphere of IIIa. The individuality of complexes Ia and
IIIa is confirmed by TLC.
1
O
Ph CH=CH C Ph + W(CO)6
Pentacarbonyl[ 2-(1,3-diphenyl-2-propen-1-one)]-
tungsten(0) and tetracarbonyl[ 4-(1,3-diphenyl-2-pro-
pen-1-one)]tungsten(0) were reacted with dialkyl hyd-
rogen phosphites. The reactions were carried out
either in a dialkyl hydrogen phosphite solution (an
almost 30-fold excess of hydrophosphoryl compound
with respect to -complex) or in benzene at a stoi-
chiometric dialkyl hydrogen phosphite: complex
ratio in the presence of a base catalyst.
Some time after the reaction onset, in the 31P NMR
spectra of the reaction mixtures we observed singlets
downfield from the signals of dialkyl hydrogen phos-
phites ( P 20.93, 16.72, 13.61, 21, and 17 ppm for Va,
Vb, Vc, VIa, and VIc, respectively). The new signals
were assigned to hydroxyphosphonates [1, 2, 8].
Ph
boiling
Ph CH=CH C
CH3CN
O
M(CO)4
IIIa
The IR spectrum of complex IIIa shows bands at
1530 cm due to the C=C bond of chalcone, coor-
dinated with tungsten, and 1620 cm due to the
carbonyl group of 1,3-diphenyl-2-propen-1-one, in-
volved in coordination. In the range of stretching
vibrations of carbon monoxide coordinated with
transition metal, there are four well-resolved
absorption bands at 1970, 1940, 1920, and 1900 cm .
The upfield shift of signals of double-bond protons
1
1
1
OH
O
Ph CH=CH C Ph + (RO)2P(O)H
Ph CH=CH
C Ph
P(OR)2
O
NEt3
W(CO)5
W(CO)5
Va Vc
OH
Ph
Ph CH=CH
C Ph
P(OR)2
O
+ (RO)2P(O)H
Ph CH=CH C
NEt3
O
W(CO)x
M(CO)4
VIa, VIc
R = CH3 (a), C2H5 (b), i-C3H7 (c).
The intensity ratio of the phosphorus signals of
phosphonates V, VI and dialkyl hydrogen phosphites,
established with time in benzene solutions, varies
from 7:1 for (i-C3H7O)2P(O)H to 10:1 for (CH3O)2
These data permit to state that complexes Ia and
IIIa enter with dialkyl hydrogen phosphites an
Abramov reaction; therewith, and the resulting
-
hydroxyphosphonates do not leave the coordination
P(O)H, which implies a 80 90% yield of phosphonate. sphere of the metal in structures Va Vc and VIa, VIc.
The IR spectrum of the mixture of the reaction pro-
duct (phosphonate) and dialkyl hydrogen phosphite
no longer shows signals of the carbonyl group of
The IR spectrum of compound Va still contain
the five well-resolved absorption bands at 2000
1
1
1
chalcone (1660 cm for Ia and 1620 cm for IIIa).
1850 cm , implying that the tungsten in Va have
1
At the same time, a broad band at 3550 cm appears,
preserved its carbonyl ligands and thus the complex
in question is mononuclear. For compound VIa, a
poorly resolved band consisting of at least of three
bands is observed in the range of stretching vibrations
of carbon monoxide coordinated with metal. This
assignable to OH stretching vibrations. The IR spec-
trum preserves bands due to stretching vibrations of
1
the C=C bonds coordinated with tungsten (1525 cm
for Ia and 1510 cm for IIIa).
1
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 71 No. 2 2001

194
KURAMSHIN et al.
picture is characteristic of some bi- and polynuclear
carbonyl complexes [9]. It is evident that in com-
pound VIa one or several molecules of carbon
monoxide begin to play the role of bridges. Due to
that the complex can increase its nuclearity, but up to
now we failed to obtain a more straightforward evi-
dence for rigorous structural assignment of compound
VIa.
were recorded on Varian UNITY 300 (298.4 MHz,
1
1H), Brucker 100 (100 MHz, H), and Brucker Gemini
1
200 (199.827 MHz, H) spectrometers at 25 C. The
chemical shifts were measured against residual proton
signals of deuterated solvents (benzene-d6, chloro-
form-d1, methanol-d4). The solution concentrations
were 0.7 1.5%. The 31P NMR spectra were recorded
on Varian UNITY 300 (121.4 MHz, 31P) and RYa
2303 (8 MHz, 31P) spectrometers against external
85% H3PO4.
It is known that the free -enones, benzalacetone
and chalcone, react with hydrophosphoryl compounds
under conditions of the Pudovik reaction with ther-
modynamic control strictly by the carbon carbon
bond to form -ketophosphonates.
Thin-layer chromatography was carried out on
Silufol plates, eluent isopropanol benzene (3:1),
development in iodine vapor.
The reason for change in the regiochemistry of
addition of dialkyl hydrogen phosphites to -enones
coordinated with metal in different ways may be
associated with change in the geometry of the coor-
dinated unsaturated ketone, capable of breaking con-
jugation between neighboring fragments of the co-
ordinated molecule [10].
Pentacarbonyl[ 2-(1,3-diphenyl-2-propen-1-
one)]tungsten(0). Hexacarbonyltungsten, 0.400 g, in
20 ml of absolute degassed THF was irradiated in a
quartz or glass flask with the UV light of a high-
pressure mercury lamp for 40 min (for 2 h in a glass
vessel) under argon and with continuous stirring. Then
a solution of 0.516 g of 1,3-diphenyl-2-propen-1-one
in 2.0 ml of THF was added, and the irradiation and
stirring were continued for an additional 2.5 h. The
reaction mixture was treated with hexane, and the
precipitate that formed was filtered off on a Schott
filter to obtain a grayish-green finely crystalline
powder, yield 22%, decomp. point 148 152 C. IR
We performed ZINDO/1 quantum-chemical cal-
2
culations of the steric structure of pentacarbonyl[
-
(1,3-diphenyl-2-propen-1-one)]tungsten(0) and tetra-
carbonyl[ 4-(1,3-diphenyl-2-propen-1-one)]tungs-
ten(0) to show that the C=C C=O fragment of
2
chalcone in the coordination sphere both of the
and
1
spectrum, , cm : 1530 (coordinated C=C); 1660
4
complex is no longer planar. The angle be-
(noncoordinated C=O from 1,3-diphenyl-2-propen-1-
one); 1990, 1970, 1940, 1920, 1900 (carbonyl ligands
tween the C=C and C=O bond planes is 27 for penta-
carbonyl[ 2-(1,3-diphenyl-2-propen-1-one)]tung-
1
bound with tungsten). H NMR spectrum: 5.3 and 6.4
4
sten(0) and 22 for tetracarbonyl[ -(1,3-diphenyl-2-
ppm (CH=CH coordinated with tungsten).
propen-1-one)]tungsten(0). It shows that strong de-
crease in conjugation between This result points to a
strongly weakened conjugation between the C=C and
C=O bonds in the coordinated chalcone. i.e. one deals
here with isolated multiple bonds. As a result, the
C=C bond in chalcone no longer exerts the electron-
acceptor effect of the C=O group; as a result, it be-
comes less electrophilic and thus inert to nucleophilic
Pentacarbonyl[ 2-(1,3-diphenyl-2-propen-1-one)]-
chromium(0), pentacarbonyl[ 2-(1,3-diphenyl-2-
propen-1-one)molybdenum(0), pentacarbonyl[ 2-(4-
2
phenyl-3-buten-2-one)]tungsten(0), pentacarbonyl[
-
(4-phenyl-3-buten-2-one)]chromium(0), and penta-
carbonyl[ 2-(4-phenyl-3-buten-2-one)]molybdenum(0)
were obtained analogously. The products all contained
attack of hydrophosphoryl compound, characteristic admixture of the 4-coordination products of -enone
of noncoordinated chalcone. This factor may be the
reason for the selective hydrophosphorylation of
heterodienes by the carbonyl group which is more
electrophilic than the coordinated C=C bond.
to metal.
Tetracarbonyl[ 4-(1,3-diphenyl-2-propen-1-
one)tungsten(0). A solution of 0.5 g of hexacar-
bonyltungsten(0) in 20 ml of acetonitrile was refluxed
in a flask, equipped with a reflux condenser, a glyce-
role seal and a gas-inlet tube, for 40 min under argon.
1,3-Diphenyl-2-propen-1-one, 0.26 g, was then added
to the reaction mixture, and the resulting solution was
refluxed for an additional 14 h, and concentrated 4
5 times in a water-jet pump vacuum without heating.
Pale green crystals precipitated and were filtered off
in an argon box to isolate a light green finely crystal-
line powder, yield 45%, decomp. point 171 175 C.
Together with the above-presented methods for
preparing -hydroxyphosphonates [1, 2, 8], their syn-
thesis in the coordination sphere of Croup VIB metals,
developed by us, extends the synthetic potential of the
Pudovik and Abramov reactions.
EXPERIMENTAL
The IR spectra were recorded on a Specord-M80
1
1
spectrometer in Vaseline oil. The H NMR spectra
IR spectrum, , cm : 1520 (coordinated C=C); 1620
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 71 No. 2 2001

HYDROPHOSPHORYLATION OF 1,3-DIPHENYL-2-PROPEN-1-ONE
195
1
(C=O of 1,3-diphenyl-2-propen-1-one coordinated
with metal); 1970, 1940, 1920, 1900 (carbonyl ligands
bound with tungsten). Tetracarbonyl[ 4-(4-phenyl-3-
buten-2-one)]tungsten(0) was obtained analogously.
IR spectrum, , cm : 1510 (coordinated C=C);
3450 br (OH); 1900 2000 (complex system of bands
from carbonyl ligands bound with tungsten). 31P
NMR spectrum of the reaction mixture:
17 ppm.
P
Reaction of pentacarbonyl[ 2-(1,3-diphenyl-2-
propen-1-one)]tungsten(0) with diethyl hydrogen
phosphite. Diethyl hydrogen phosphite, 0.2 ml, and
1 2 drops of triethylamine were added to a solution
of 0.20 g of pentacarbonyl[ 2-(1,3-diphenyl-2-propen-
1-one)]tungsten(0) in 5 ml of absolute benzene. The
resulting mixture was kept for 48 h at room tempera-
ture under argon. The benzene was removed in a
water-jet-pump vacuum until a viscous amorphous
material formed. The yield of -hydroxyphosphonate
was 75% (from the 31P NMR spectrum of the reaction
The reactions of tetracarbonyl[ 4-(1,3-diphenyl-2-
propen-1-one)]tungsten(0) with dimethyl and diiso-
propyl hydrogen phosphites were carried out analo-
gously.
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