Electrophilic aromatic substitution reactions of a tungsten-coordinated phosphirenyl triflate

Article abstract of DOI:10.1021/om401050w

The phosphirenyl cation complex [W(CO)₅{PC(Ph)C(Ph)}] ⁺ (2) is formed by chloride abstraction from the chlorophosphirene complex [W(CO)₅{P(Cl)C(Ph)C(Ph)}] (1) with excess AlCl₃. The phosphirenyl triflate complex [W(CO)₅{P(OSO₂CF ₃)C(Ph)C(Ph)}] (3) is formed by reaction of the chlorophosphirene complex with AgOSO₂CF₃ and is in equilibrium with and typically reacts in the same fashion as the phosphirenyl cation. Reaction of 3 with diethylaniline or anisole leads to electrophilic aromatic substitution preferentially at the para position. Reaction with N,N-dimethyl-p-toluidine, in which the para position is blocked, leads to exclusive ortho substitution. The resulting 1,2-substituted arene can adopt a P,N bidentate coordination mode if a CO is removed from tungsten via photolysis. Compound 3 reacts with aromatic heterocycles thiophene, furan, and pyrrole, leading exclusively to substitution in the 2 position, with no evidence for P-S, P-O, or P-N bond formation. Reaction with indole led to substitution at the 3 position, also with no evidence for P-N bond formation. However, upon chromatographic purification, the substituted indole product decomposes into a disubstituted product, with W-coordinated phosphirenyl units at the 3 position and at N. Reaction with phenol and diphenyl amine led exclusively to P-O and P-N bond formation, with no evidence for aromatic substitution. Phosphine products can be removed via oxidation of W with I₂, followed by displacement with bipyridine. A computational study shows that coordination to W(CO)₅ greatly enhances electrophilicity at P in phosphenium ions, leading to the observed rapid electrophilic substitution reactions.

Full text of DOI:10.1021/om401050w

Article
pubs.acs.org/Organometallics
Electrophilic Aromatic Substitution Reactions of a Tungsten-
Coordinated Phosphirenyl Triflate
Arumugam Jayaraman and Brian T. Sterenberg*
Department of Chemistry and Biochemistry, University of Regina, 3737 Wascana Parkway, Regina, Saskatchewan, Canada S4S 0A2
S
* Supporting Information
ABSTRACT: The phosphirenyl cation complex [W(CO)5{PC-
(Ph)C(Ph)}]+ (2) is formed by chloride abstraction from the
chlorophosphirene complex [W(CO)5{P(Cl)C(Ph)C(Ph)}] (1)
with excess AlCl3. The phosphirenyl triflate complex [W-
(CO)5{P(OSO2CF3)C(Ph)C(Ph)}] (3) is formed by reaction
of the chlorophosphirene complex with AgOSO2CF3 and is in
equilibrium with and typically reacts in the same fashion as the
phosphirenyl cation. Reaction of 3 with diethylaniline or anisole
leads to electrophilic aromatic substitution preferentially at the
para position. Reaction with N,N-dimethyl-p-toluidine, in which
the para position is blocked, leads to exclusive ortho substitution.
The resulting 1,2-substituted arene can adopt a P,N bidentate
coordination mode if a CO is removed from tungsten via
photolysis. Compound 3 reacts with aromatic heterocycles thiophene, furan, and pyrrole, leading exclusively to substitution in the
2 position, with no evidence for P−S, P−O, or P−N bond formation. Reaction with indole led to substitution at the 3 position,
also with no evidence for P−N bond formation. However, upon chromatographic purification, the substituted indole product
decomposes into a disubstituted product, with W-coordinated phosphirenyl units at the 3 position and at N. Reaction with
phenol and diphenyl amine led exclusively to P−O and P−N bond formation, with no evidence for aromatic substitution.
Phosphine products can be removed via oxidation of W with I2, followed by displacement with bipyridine. A computational study
shows that coordination to W(CO)5 greatly enhances electrophilicity at P in phosphenium ions, leading to the observed rapid
electrophilic substitution reactions.
influence the steric environment and enhance regioselectivity.
Depending on the nature of the metal complex, the bonding in
planar metal coordinated PR2 units can range between two
extremes, four-electron phosphido, favored for electron-rich
metals, or phosphenium, favored for electron-poor metals.6 A
four-electron phosphido complex has a formal PM double
bond and exhibits the reactivity expected for metal−element
multiple bonds.7 The phosphenium ion complex, on the other
hand, is formally electron deficient and electrophilic at P.8
We initially chose to focus on metal complexes of the
phosphirenyl cation because aromatic delocalization provides
additional stability to the phosphenium ion.9 The first metal
complex of a phosphirenyl cation was a nickel complex
containing an η3-phosphirenyl cation, formed by condensation
of vaporized atomic nickel with tert-butylphosphaalkyne.10 An
η1-pentacarbonyltungsten complex, reported by Regitz et al.,
was prepared by abstraction of triflate from a phosphirenyl
triflate complex using B(OTf)3 in liquid SO2 at −78 °C.11
However, the reactivity of metal-coordinated phosphirenyl
cations remained unexplored. In a recent communication,12 we
described the formation and characterization in solution of the
INTRODUCTION
■
Aromatic carbon−phosphorus bond formation is a key step in
the synthesis of many organophosphorus compounds.1 Aryl
carbon−phosphorus bonds are commonly formed using
nucleophilic substitution reactions, often involving organo-
metallic reagents such as aryl lithium or Grignard reagents, and
ClPR2 electrophiles.2 An alternative approach, which avoids the
strongly basic conditions of the previous reactions, is a Friedel−
Crafts-like electrophilic aromatic substitution using ClPR2 and a
Lewis acid such as AlCl3.3,4 Although these reactions were first
recognized many years ago,5 they have not gained as
widespread applicability, possibly because they are relatively
slow and low yielding.1 These reactions involve in situ
+
generation of a phosphenium ion (PR2 ), and we were
interested in the possibility of enhancing the electrophilicity
of the phosphenium ions by generating them in the
coordination sphere of a transition metal. Metal coordination
provides several potential advantages. The metal complex can
act as a protecting group for the phosphorus lone pair.
Coordination to an electron poor metal complex may enhance
electrophilicity as P-to-M σ donation reduces electron density
at phosphorus. The metal complex can also enhance the
stability of a phosphenium intermediate by providing steric
protection and π-back-donation, and the metal complex may
Received: October 29, 2013
© XXXX American Chemical Society
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a
W(CO)5-complexed phosphirenyl cation [W(CO)5{PC(Ph)C-
(Ph)}]+. We have shown that the phosphirenyl cation complex
reacts as a metal-coordinated phosphenium ion. It is highly
electrophilic and undergoes electrophilic substitution reactions,
including an electrophilic aromatic substitution with ferrocene
at ambient temperature (Scheme 1). We further showed that
Scheme 2
Scheme 1
a
Reagents and conditions: (i) N,N-diethylaniline, 2 equiv, RT,
CH2Cl2; (ii) N,N-dimethyl-p-toluidine, 2 equiv, RT, CH2Cl2.; (iii)
photolysis, THF, 2.5 h; (iv) anisole, 4 equiv, CH2Cl2, 45 °C, 12 h. [W]
= W(CO)5.
the phosphirenyl triflate [W(CO)5{P(OSO2CF3)C(Ph)C-
(Ph)}] acts as a surrogate for the phosphirenyl cation, showing
the same electrophilic substitution reactions, but also showing
much greater functional group tolerance. In this follow-up
paper, we will further examine the electrophilic aromatic
substitution reactions of the phosphirenyl triflate to detail the
scope and functional group tolerance of this reaction and to
probe its utility in P−C bond forming reactions.
carbonyl region consistent with a W(CO)5 fragment. The
structure of 5 was confirmed by X-ray crystallography, and an
ORTEP diagram is shown in Figure 1. The structure consists of
a W(CO)5 unit coordinated by the 4-aminophenyl phosphir-
ene. All distances and angles are as expected.
RESULTS
■
The precursor to the phosphirenyl cation and phosphirenyl
triflate complexes is the known chlorophosphirene complex
[W(CO)5{P(Cl)C(Ph)C(Ph)}] (1).13 It was formed via a
simplified route.12 Reaction of W(CO)5 with diisopropyla-
2−
mino-dichlorophosphine leads to a transient aminophosphini-
dene, which was trapped with diphenylacetylene, leading to the
aminophosphirene complex. The aminophosphirene was
converted to the chlorophosphirene by reaction with HCl(g).
Compound 1 is converted to the metal-complexed phosphir-
enyl cation 2 via reaction with excess AlCl3. Compound 2 can
be observed in solution, but not isolated. The phosphirenyl
triflate 3 is formed by reaction of 1 with AgOSO2CF3 and also
formed in situ, but not isolated due to its extreme sensitivity.
Reaction of N,N-diethylaniline with the phosphirenyl cation
2 led to decomposition, likely as a result of the excess AlCl3
needed to generate 2. However, reaction with the phosphirenyl
triflate 3 resulted in clean electrophilic aromatic substitution in
the para position, leading to the 4-anilinyl phosphirene complex
5 as the sole product (Scheme 2). There was no evidence in the
reaction solution for ortho-substituted product. The 31P{1H}
NMR spectrum of 5 shows a peak at δ −157.9, with 183W
Figure 1. ORTEP diagram showing the X-ray crystal structure of 5.
Thermal ellipsoids are shown at the 50% level, and hydrogen atoms
have been omitted. Selected distances and angles: W1−P1 =
2.5083(4), P1−C30 = 1.809(2), P1−C6 = 1.790(2), P1−C7 =
1.793(2), C6−C7 = 1.323(2). W1−P1−C6 = 125.63(5), W1−P1−C7
= 125.32(5), C7−P1−C6 = 43.34(8), P1−C6−C7 = 68.5(1), P1−
C7−C6 = 68.2(1).
1
satellites and a JWP of 265 Hz. This peak falls in the typical
low-field region for phosphirenes,14 showing that the three-
membered ring is maintained, while the tungsten coupling
1
confirms that it is still metal coordinated. In the H-coupled
spectrum, this peak is split into a triplet by two equivalent ortho
H atoms (3JPH = 11.9 Hz), consistent with para substitution.
The phenyl region of the 1H NMR spectrum shows an AA′XX′
pattern as expected for a para-substituted phenyl ring, as well as
peaks for N-bound ethyl groups and the phenyl groups on the
phosphirene ring. The IR spectrum shows a pattern in the
The reaction of 3 with N,N-diethylaniline led exclusively to
para substitution. However, electrophilic substitution can also
be easily directed to the ortho position by blocking the para
position. Reaction of 3 with N,N-dimethyl-p-toluidine leads to
the 2-anilinyl phosphirene complex 6 as the sole product
(Scheme 2). The 1H NMR spectrum of 6 shows peaks for three
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inequivalent phenyl hydrogen atoms, with couplings consistent
both isomers have the same Rf value; therefore, only the major
product 8a was isolated in 58% yield by recrystallization from
the mixture.
with a 1, 2, 4 substitution. The coupled 31P NMR spectrum of 6
3
shows a doublet of doublets at δ −155.2, with JPH = 13.4 Hz
4
and JPH = 4.4 Hz, as expected for ortho substitution.
The reactivity of the phosphirenyl cation 2 and the
phosphirenyl triflate 3 toward other aromatic compounds
with nonactivating or deactivating substituents was also
explored. The triflate 3 showed no reactivity toward
naphthalene or chlorobenzene. Higher temperature (50 °C)
led to decomposition, and no phosphorus-containing products
could be isolated. Reaction with the phosphirenyl cation 2 led
to decomposition even at RT. Neither 2 nor 3 reacted with
toluene.
In addition to arenes, we have examined electrophilic
substitution reactions with hereroaromatic substrates. Reaction
of 3 with thiophene resulted in electrophilic substitution at the
2 position, leading to the 2-thienyl phosphirene complex 9
Substitution at the position meta to N can be ruled out by
the subsequent products. Other spectral features are similar to
those of 5.
The 1,2-disubstituted arene in 6 is a potential bidendate P,N
ligand. Photolysis of 6 in THF resulted in a dissociation of a cis
carbonyl and coordination of the amine to form the chelated
complex 7 (Scheme 2). Upon chelation, the 31P NMR
resonance moves downfield to δ −118.2, while the IR spectrum
now shows four peaks at 2015, 1893, 1889, and 1852 cm−1, in a
pattern consistent with cis-L2M(CO)4 substitution. The 13C
NMR spectrum shows three carbonyl environments at δ 203.7
(2JCP = 10.0 Hz), 210.8 (2JCP = 8.8 Hz), and 211.1 (2JCP = 41.7
Hz), which correspond to two carbonyls cis to P and N ligands,
one carbonyl trans to N, and one carbonyl trans to P,
respectively, further confirming the cis bidentate coordination
of the P,N ligand. Compound 7 has been structurally
characterized, and an ORTEP diagram is shown in Figure 2.
a
Scheme 3
a
Reagents and conditions: CH2Cl2, RT, (i) thiophene, 3 equiv, (ii)
furan, 3 equiv, (iii) 2,5-dimethylfuran, 2 equiv, NEt3, 1 equiv, (iv)
pyrrole, 4 equiv, (v) indole, 1 equiv. [W] = W(CO)5.
Figure 2. ORTEP diagram showing the X-ray crystal structure of 7.
One of two crystallographically inequivalent molecules is shown.
Hydrogen atoms have been omitted for clarity. Thermal ellipsoids are
shown at the 50% probability level. Selected distances and angles:
W1−P1 = 2.4440(6), W1−N1 = 2.390(2), P1−C5 = 1.788(2), P1−
C6 = 1.787(2), C5−C6 = 1.322(3), P1−C9 = 1.821(2), N1−C10 =
1.487(3), W1−P1−C9 = 105.37(8), P1−C9−C10 = 118.8(2), W1−
N1−C10 = 117.0(1), N1−C10−C9 = 120.6(2), P1−C5−C6 =
68.2(1), P1−C6−C5 = 68.4(2), C5−P1−C6 = 43.4(1).
(Scheme 3). The 31P NMR spectrum of 9 gives a singlet with
183W satellites at δ −171.7 (1JPW = 279 Hz). In the 1H-coupled
spectrum, this peak is split into a doublet with a 3JPH of 7.4 Hz,
consistent with substitution in the 2 position (substitution in
the 3 position would lead to a doublet of doublets). The
structure of 9 was also confirmed by X-ray crystallography, and
an ORTEP diagram is shown in Figure 3. The structure consists
of a W(CO)5 unit coordinated by the 2-thienyl phosphirene
ligand. All distances and angles are as expected.
The structure consists of a W(CO)4 unit with a cis bidentate
P,N ligand and also confirms substitution ortho to N in the
formation of 6. All distances and angles are as expected.
Addition of anisole to 3 at room temperature resulted in no
detectable reaction. However, at 45 °C, 3 reacts to form two
products in an 85:15 ratio, which were shown to be products of
para and ortho substitution, respectively (Scheme 2). The 31P
NMR spectrum of the reaction mixture shows peaks at δ
−159.8 (85%) and δ −165.6 (15%). In the 1H-coupled
Compound 3 reacts with furan in the same way as it reacts
with thiophene, leading to the 2-furanyl phosphirene complex
10 (Scheme 3). The 31P{1H} NMR spectrum of 10 gives a
singlet with 183W satellites at δ −178.6 (1JPW = 280 Hz), which,
like that of 9, splits into a doublet in the coupled spectrum,
1
supporting substitution in the 2 position. The H NMR shows
two peaks at δ 6.40 and 6.79, which correspond to the H atoms
in the 3 and 4 positions. The H atom in the 5 position is
obscured by the phenyl resonances. Substitution can also be
directed to the 3 position by blocking the 2 position. Reaction
of 3 with 2,5-dimethylfuran led to the 3-furanyl phosphirene
complex 11. Compound 11 was characterized in solution, but
decomposed upon attempted workup into the known
3
spectrum, the major signal is split into a triplet, with a JPH of
13.1 Hz, allowing us to assign it as the para-substituted product.
3
The minor signal is split into a doublet of doublets, with JPH
and 4JPH values of 11.9 and 4.7 Hz, respectively, and is assigned
as the ortho-substituted product. Attempts to separate the
regioisomers by flash chromatography were not successful, as
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tionates into indole and the disubstituted indole 14, which has
W-coordinated phosphirenyl units in both the 3 position and
on N (Scheme 4). The 31P NMR spectrum of 14 shows two
Scheme 4
peaks at δ −173.8 and −129.8. The first peak is very close to
that of the precursor 13 and corresponds to the phosphirenyl
unit in the 3 position. The second peak, at δ −129.8, falls in the
typical range for N-substituted phosphirenyl tungsten com-
plexes and is assigned as the N-bound phosphirenyl unit.
Additional evidence for N substitution comes from the
disappearance of the N−H peak from the H NMR spectrum.
The same product can also be made rationally by reaction of
indole with two equivalents of 3.
Figure 3. ORTEP diagram showing the crystal structure of 9. One of
two crystallographically inequivalent molecules is shown. Hydrogen
atoms have been omitted for clarity. Thermal ellipsoids are shown at
the 50% probability level. Selected distances and angles: W1−P1 =
2.4783(8), P1−C6 = 1.800(3), P1−C10 = 1.789(3), P1−C11=
1.791(3), C10−C11 = 1.327(4). W1−P1−C6 = 120.88(9), W1−P1−
C10 = 126.3(1), C10−P1−C11 = 43.5(1), P1−C10−C11 = 68.3(2),
P1−C11−C10 = 68.2(2).
1
Reactions with phenol, diphenyl amine, and triphenyl
phosphine demonstrate the functional group limits of the
methodology. Reaction with phenol resulted in P−O bond
formation, leading to the phenoxyphosphirene 15 in 87%
hydroxyphosphirene complex [W(CO)5{P(OH)C(Ph)C-
(Ph)}].15 The 1H NMR spectrum of 11 shows two inequivalent
methyl groups at δ 2.16 and 2.25 and a peak for the H in the 4
position at δ 5.95 (3JPH = 2.3 Hz), showing P substitution in the
3 position. It is not clear why 11 is significantly more sensitive
to hydrolysis than the other products.
isolated yield (Scheme 5). The resonance at δ −67.2 in the 31
P
Scheme 5
The reaction of 3 with nitrogen heterocycles containing N−
H could potentially lead to electrophilic aromatic substitution
or to P−N bond formation. In the reaction of 3 with pyrrole,
however, the reaction mixture showed exclusively aromatic
substitution at the 2 position, leading to the 2-pyrrolyl
phosphirene complex 12 (Scheme 3). There was no evidence
for N substitution. The 31P NMR spectrum of 12 shows a peak
at δ −174.6, consistent with the resonances of other C-
substituted arylphosphirene compounds,3 but distinctly differ-
ent from N-substituted tungsten phosphirene complexes, which
typically occur in the range δ −100 to −130.16 Further, the 1H
NMR spectrum shows an NH resonance at δ 8.41, as well as
three inequivalent pyrrole CH environments, confirming
substitution at C rather than N.
Like pyrrole, indole reacts with 3 to give exclusively
electrophilic aromatic substitution, in this case at the 3 position,
leading to the 3-indolylphosphirene complex 13 (Scheme 3).
The 31P{1H} NMR spectrum shows a singlet with W satellites
at δ −172.5, very close to the shift observed for the pyrrole
addition product, consistent with P−C bond formation.
Substitution at the 3 position was confirmed by assignment
of the 1H and 13C NMR spectra and the presence of H−P and
C−P coupling in the expected resonances. Again, there was no
evidence for a N-substituted product in the reaction solution.
Unlike the other heterocycles, in indole the 3 position is
activated, and this is the expected site for electrophilic
substitution.
NMR spectrum of 15 is highly deshielded when compared with
the other phosphirenes obtained in this study and is similar to
the resonance (δ −72.9) of a known ethoxy phosphirene
complex,16 confirming P−O bond formation. Similarly, reaction
with diphenylamine led to P−N bond formation and the
aminophosphirene complex 16 (Scheme 5). As reported
previously,12 triphenylphosphine simply coordinates to the
phosphirenyl phosphorus, leading to cationic adduct 17.
The successful substitution of the phosphirenyl electrophile
at an ortho position to the amino group of N,N-dimethyl-p-
toluidine to form 6 and the subsequent chelation reaction by
ligand displacement to form 7 prompted us to investigate the
decomplexation of the chelating P,N ligand from 6. Previous
studies have shown that several monodentate phosphine
Compound 13 was purified using flash chromatography on
alumina. However, earlier attempts to purify it using silica gel
revealed an interesting transformation in which 13 dispropor-
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ligands, including phosphirenes, can be decomplexed by
oxidation of the transition metal with iodine followed by the
addition of a hard ligand.17 This method was adopted to
decomplex the chelating P,N ligand from 6. Treatment of 6
with 1 equiv of iodine in CH2Cl2 resulted in oxidative addition
of the I2 to W. However, in this case oxidative addition was
accompanied by loss of two carbonyls, and the observed
product was the P,N-chelated 2-anilinyl phosphirene W(II)
complex 18 (Scheme 6). The identity of 18 as a chelated
DISCUSSION
■
The reactions described here demonstrate that the phosphir-
enyl triflate complex 3 is a powerful reagent for P−C bond
formation and undergoes electrophilic aromatic substitution
reaction under very mild conditions without added Lewis acid.
This facile reactivity strongly supports an equilibrium between
3 and 2, as previously suggested for these compounds12 and for
other phosphine triflates.11,18 Comparison to typical conditions
for electrophilic addition by non-metal-coordinated phosphines
suggests that metal coordination greatly enhances the electro-
philicity, resulting in reactions that can be carried out under
much milder conditions. For example, typical conditions for
addition of ClPPh2 to ferrocene using AlCl3 are 107 °C for 24 h
with 59% yield.4 In contrast, the tungsten phosphirenyl
complex 2 and the triflate complex 3 add to ferrocene
instantaneously at RT. The enhanced electrophilicity upon
metal coordination is supported by computational chemistry,
which shows a substantial increase in the positive charge at P
upon metal coordination.
Scheme 6
Electrophilic addition reactions of the phosphirenyl triflate
complex 3 require an activated aromatic system and thus far
have a lower reactivity limit at anisole. Less activated substrates
do not react. The phosphirenyl cation complex 2 is reactive
toward a wider range of substrates, but the harsher conditions
needed to form 2 typically lead to decomposition, except in the
case of ferrocene. Raising the temperature to increase the
reactivity of 3 also led to decomposition. The facile
decomposition may be a function of the strained ring in the
phosphirene product, and expansion of this methodology to
other PR2 phosphenium ion complexes, currently under way in
our laboratory, will allow reactivity with a wider range of less
activated substrates.
The methodology described here has good functional group
tolerance. It is compatible with tertiary amines and ethers that
lack N−H or O−H bonds, but not with secondary amine or
alcohols. In contrast, aromatic heterocycles that contain N−H
bonds are compatible, and additions to pyrrole and indole are
selective for the C−H bonds. Here, the lower basicity that
results from aromaticity prevents the N to P coordination that
is the likely first step in P−N bond formation. In the case of
indole, P−N bond formation does occur, but as the second
reaction after electrophilic substitution in the 3 position. The
regioselectivity of these reactions is also excellent. For all room-
temperature reactions, single regioisomers are observed.
However, at the higher temperature required in the anisole
reaction, regioselectivity drops, and 15% of the minor ortho
isomer is observed.
complex was confirmed by reaction of the chelated W(0)
complex 7 with iodine, which leads to the same product 18.
Addition of 1 equiv of 2,2′-bipyridine to 18 in CH2Cl2 then
leads to the targeted free ligand 19 (Scheme 6).
Coordination of the phosphenium cation to the W(CO)5
appears to significantly enhance its electrophilicity and to
facilitate electrophilic aromatic substitution. In order to test this
hypothesis and to understand the nature of the W−P bond,
DFT computations were carried out at the B3LYP level of
theory on the phosphirenyl complex 2 and on the free
phosphirenyl cation. The optimized structure of 2 was already
published and suggested that the phosphirenyl cation is
stabilized by aromatic delocalization in the phosphirene ring,
as well as by some tungsten to phosphorus π-back-donation.
The interactions are apparent from the P−C and P−W bond
shortening upon formation of the cation.12 A comparison of the
NBO charges for the phosphirenyl cation complex and the
metal-free phosphirenyl cation shows that in both cases the
positive charge is primarily localized on P (complexed: +1.234;
free: +0.901). However, the P atom in the metal complex has a
significantly larger positive charge (difference = +0.333). The
charge increase on P is balanced by an overall negative charge
of −0.223 on the W(CO)5 fragment, which indicates that the
increased charge on P in the complex can be primarily
attributed to P-to-W σ-donation. The charge transfer that
results from σ-donation to the metal will be counteracted by π-
back-donation from the metal to phosphorus; however, back-
donation from the W(CO)5 unit is apparently not sufficient to
alleviate the resulting positive charge buildup on P.
In conclusion, we have shown that the phosphirenyl cation
complex and its surrogate, the phosphirenyl triflate complex,
are versatile reagents for phosphorus−carbon bond formation
via electrophilic aromatic substitution. We have also demon-
strated the potential applicability of this chemistry by using it to
synthesize a novel bidentate P,N ligand.
EXPERIMENTAL SECTION
■
General Comments. All procedures except flash chromatography
were carried out using standard Schlenk techniques or in a glovebox
under a nitrogen atmosphere. Diethyl ether, pentane, and THF were
distilled from Na/benzophenone. Dichloromethane was purified using
solvent purification columns containing alumina, followed by vacuum
distillation from P2O5. CDCl3 was vacuum distilled from P2O5.
Solvents for flash chromatography were not purified. Photolysis
reactions were carried out in Pyrex vessels using a Rayonet
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photochemical reactor equipped with nine lamps having a maximum
output at 260 nm. The NMR spectra were recorded on a Varian
Mercury 300 spectrometer at 300.177 MHz (1H), 121.514 MHz (31P),
or 75.479 MHz (13C{1H}) in CDCl3. IR spectra were recorded in
CH2Cl2. Elemental analyses were not obtained for compounds 11, 18,
and 19 due to low stability in the solid state. Their spectra are given in
the Supporting Information. The compound [W(CO)5{P(Cl)C(Ph)-
C(Ph)}] (1) was prepared according to the published procedure.12
a. Generation of [W(CO)5{P(OSO2CF3)C(Ph)C(Ph)}] (3) in Solution.
The compound [W(CO)5{P(Cl)C(Ph)C(Ph)}] (1, 30.0 mg, 0.053
mmol) and AgOSO2CF3 (13.6 mg, 0.053 mmol) were dissolved in
CH2Cl2 (4 mL). The solution was stirred for 15 min, resulting in a
colorless solution and a white precipitate. The solution was filtered
through Celite. Yield is quantitative by NMR spectroscopy. The
dichloromethane solution was stable for days at −20 °C or hours at
room temperature, but decomposed rapidly upon crystallization. This
reaction was also carried out in CDCl3 for NMR spectroscopy. IR
(νCO, CH2Cl2, cm−1): 2078(w), 1946(vs). 31P{1H} NMR (CDCl3): δ
trans-CO). Anal. Calcd for C28H22NO5PW: C, 50.40; H, 3.32; N, 2.10.
Found: C, 50.49, H, 3.34; N, 2.18.
d. Synthesis of [W(CO)4{P{C6H3(2-N(CH3)2)(5-CH3)}C(Ph)C(Ph)-
κ2P,N}] (7). Compound 6 (40.0 mg, 0.060 mmol) was dissolved in 3
mL of THF and irradiated with UV for 2.5 h. The solvent was then
removed under reduced pressure, and the residue was extracted into
CH2Cl2 (0.5 mL) and crystallized as yellow crystals by slow diffusion
of pentane into a saturated CH2Cl2 solution. Yield: 37 mg, 96%. IR
(νCO, CH2Cl2, cm−1): 2015(w), 1893(s), 1889(s), 1852(s). 31P NMR
(CDCl3): δ −118.2 (dd, 1JPW = 296 Hz, 3JPH = 9.6 Hz, 4JPH = 3.6 Hz).
1H NMR (CDCl3): δ 2.19 (s, 3H, C6H3CH3), 3.62 (s, 6H, N(CH3)2),
6.75 (m, 1H, arene CH), 7.21 (m, 1H, arene CH), 7.47−7.96 (m,
11H, 10H of Ph and 1H of arene). 13C NMR (CDCl3): δ 20.78 (s,
2
C6H3CH3), 62.37 (s, N(CH3)2), 119.28 (d, JCP = 8.2 Hz, arene C),
1
3
124.87 (d, JCP = 11.7 Hz, arene C), 127.49 (d, JCP = 5.9 Hz, arene
C), 129.05 (s, ipso-Ph), 129.52 (s, Ph), 130.80 (s, Ph), 130.86 (s, Ph),
4
132.57 (d, arene C), 137.45 (d, JCP1 = 1.1 Hz, arene C), 137.54 (d,
2JCP = 5.2 Hz, arene C), 159.79 (d, JCP = 23.5 Hz, phosphirene ring
1
−52.7 (s, JPW = 350.1 Hz). 19F NMR (CDCl3): δ −76.7 (s,
2
2
C), 203.74 (d, JCP = 10.0 Hz, cis CO), 210.79 (d, JCP = 8.8 Hz, CO
trans to N), 211.05 (d, 2JCP = 41.7 Hz, CO trans to P). Anal. Calcd for
C27H22NO4PW: C, 50.73; H, 3.47; N, 2.19. Found: C, 50.41; H, 3.48;
N, 2.27.
OSO2CF3). 1H NMR (CDCl3): δ 7.62−8.03 (m, Ph). 13C NMR
(CDCl3): δ 118.5 (q, 1JCF = 319.0 Hz, OSO2CF3), 125.8 (d, 2JCP = 3.5
Hz, ipso-Ph), 129.9 (s, Ph), 130.6 (s, Ph), 130.7 (s, Ph), 130.7 (s, Ph),
132.8 (s, Ph), 147.0 (d, 1JCP = 20.2 Hz, phosphirene ring C), 193.4 (d,
e. Synthesis of [W(CO)5{P(p-C6H4OCH3)C(Ph)C(Ph)}] (8a). A
solution of [W(CO)5{P(OSO2CF3)C(Ph)C(Ph)}] (3) prepared
from [W(CO)5{P(Cl)C(Ph)C(Ph)}] (1, 50.0 mg, 0.088 mmol) and
AgOSO2CF3 (22.6 mg, 0.088 mmol) in CH2Cl2 (2 mL) as described
above was transferred to a Teflon-capped NMR tube. Anisole (38 μL,
0.352 mmol) was added, and the tube was sealed. The solution was
then heated at 45 °C for 12 h, resulting in a color change to yellow.
The solvent was removed under reduced pressure. The residue was
purified by flash chromatography (alumina, 10/90 v/v diethyl ether/
pet. ether), and the yellow fraction collected was shown to contain a
mixture of para (85%, 8a) and ortho (15%, 8b) substituted product.
Cooling a saturated pentane solution of the mixture to −20 °C led to
yellow crystals of the major product 8a. Yield: 33 mg, 58%. IR (νCO,
CH2Cl2, cm−1): 2074(w), 1941(vs). 31P NMR (CDCl3): δ −159.8 (t,
2
2JCP = 9.2 Hz, cis-CO), 196.3 (d, JCP = 51.2 Hz, trans-CO).
b. Synthesis of [W(CO)5{P(p-C6H4N(CH2CH3)2)C(Ph)C(Ph)}] (5). A
solution of [W(CO)5{P(OSO2CF3)C(Ph)C(Ph)}] (3) was prepared
from [W(CO)5{P(Cl)C(Ph)C(Ph)}] (1, 70.0 mg, 0.123 mmol) and
AgOSO2CF3 (31.6 mg, 0.123 mmol) in CH2Cl2 (6 mL) as described
above. N,N-Diethylaniline (39 μL, 0.246 mmol) was then added,
resulting in a color change to yellow. The solvent was removed under
reduced pressure, and the residue was purified by flash chromatog-
raphy (alumina, 25/75 v/v diethyl ether/petroleum ether). The yellow
product was crystallized by cooling a saturated diethyl ether/pentane
solution to −20 °C. Yield: 65 mg, 78%. IR (νCO, CH2Cl2, cm−1):
1
2070(w), 1937(vs). 31P NMR (CDCl3): δ −157.9 (t, JPW = 265 Hz,
1
3
3JPH = 11.9 Hz). H NMR (CDCl3): δ 1.02 (t, 6H, JHH = 6.9 Hz,
3
1
1JPW = 268 Hz, JPH = 13.0 Hz). H NMR (CDCl3): δ 3.78 (s, 3H,
OCH3), 6.88 (m, 2H, arene CH), 7.41−7.91 (m, 12H, 10H of Ph and
2H of arene). 13C NMR (CDCl3): δ 55.57 (s, −OCH3), 114.39 (d, JCP
= 11.4 Hz, arene C), 127.56 (d, JCP = 6.7 Hz, arene C), 128.40 (d, 1JCP
= 9.9 Hz, arene C), 128.81 (d, 2JCP = 8.8 Hz, ipso-Ph), 129.55 (s, Ph),
3
NCH2CH3), 3.22 (q, 4H, JHH = 6.9 Hz, NCH2CH3), 6.49 and 7.22
3
3
(AA′XX′, JAX = 9.0 Hz, JXP = 12.6 Hz, arene CH), 7.33−7.80 (m,
10H, Ph). 13C NMR (CDCl3): δ 12.67 (s, NCH2CH3), 44.56 (s,
2
1
NCH2CH3), 111.20 (d, JCP = 11.5 Hz, arene C), 120.26 (d, JCP
=
14.4 Hz, arene C), 128.01 (d, 3JCP = 6.9 Hz, arene C), 129.21 (d, 2JCP
= 8.6 Hz, ipso-Ph), 129.41 (s, Ph), 130.48 (s, Ph), 130.49 (s, Ph),
130.57 (s, Ph), 133.29 (d, 1JCP = 17.3 Hz, phosphirene ring C), 149.56
1
130.53 (s, Ph), 130.61 (s, Ph), 130.79 (s, Ph), 133.21 (d, JCP = 17.1
4
Hz, phosphirene ring C), 161.93 (d, JCP = 2.1 Hz, arene C), 196.28
4
2
(d, 2JCP = 8.8 Hz, 1JCW = 125.6 Hz, cis-CO), 198.14 (d, 2JCP = 30.6 Hz,
trans-CO). Anal. Calcd for C26H17O6PW: C, 48.78; H, 2.68. Found: C,
49.03; H, 2.74.
(d, JCP = 1.7 Hz, ipso-C6H4N(CH2CH3)2), 196.57 (d, JCP = 8.6 Hz,
1JCW = 125.5 Hz, cis-CO), 198.59 (d, 2JCP = 29.4 Hz, trans-CO). Anal.
Calcd for C29H24NO5PW: C, 51.12; H, 3.55; N, 2.06. Found: C, 51.27;
H, 3.68; N, 2.13.
f. Synthesis of [W(CO)5{P(2-C4H3S)C(Ph)C(Ph)}] (9). A solution of
[W(CO)5{P(OSO2CF3)C(Ph)C(Ph)}] (3) was prepared from [W-
(CO)5{P(Cl)C(Ph)C(Ph)}] (1, 50.0 mg, 0.088 mmol) and
AgOSO2CF3 (22.6 mg, 0.088 mmol) in CH2Cl2 (5 mL) as described
above. Thiophene (21 μL, 0.264 mmol) was added, resulting in a color
change to yellow. The solvent was removed under reduced pressure,
and the residue was purified by flash chromatography (silica, 20/80 v/
v diethyl ether/petroleum ether). The yellow product was crystallized
by cooling a saturated CH2Cl2/pentane solution to −20 °C. Yield: 38
mg, 70%. IR (νCO, CH2Cl2, cm−1): 2075(w), 1945(vs). 31P NMR
c. Synthesis of [W(CO)5{P{C6H3(2-N(CH3)2)(5-CH3)}C(Ph)C(Ph)}]
(6). A solution of [W(CO)5{P(OSO2CF3)C(Ph)C(Ph)}] (3) was
prepared from [W(CO)5{P(Cl)C(Ph)C(Ph)}] (1, 90.0 mg, 0.158
mmol) and AgOSO2CF3 (40.7 mg, 0.158 mmol) in CH2Cl2 (6 mL) as
described above. N,N-Dimethyl p-toluidene (46 μL, 0.318 mmol) was
added, resulting in a color change to yellow. The solvent was removed
under reduced pressure, and the residue was purified by flash
chromatography (alumina, 30/70 v/v diethyl ether/petroleum ether)
and crystallized as yellow crystals by cooling a saturated pentane
solution to −20 °C. Yield: 86 mg, 82%. IR (νCO, CH2Cl2, cm−1):
2070(w), 1937(vs). 31P NMR (CDCl3): δ −155.2 (dd, 1JPW = 270 Hz,
3
1
1
(CDCl3): δ −171.7 (d, JPH = 7.4 Hz, JPW = 279 Hz). H NMR
(CDCl3): δ 7.03 (m, 1H, C4H3S), 7.32 (m, 1H, C4H3S), 7.40−7.84
(m, 11H, 10H of Ph and 1H of C4H3S). 13C NMR (CDCl3): δ 126.98
(d, JCP = 6.0 Hz, C4H3S), 128.77 (d, JCP = 10.5 Hz, C4H3S), 129.45 (d,
ipso-Ph), 129.56 (s, Ph), 130.52 (s, Ph), 130.60 (s, Ph), 130.96 (s, Ph),
132.24 (d, JCP = 1.7 Hz, C4H3S), 135.86 (d, JCP = 15.5 Hz,
phosphirene ring C), 142.52 (d, JCP = 4.4 Hz, C4H3S), 195.90 (d, 2JCP
4
1
3JPH = 13.4 Hz, JPH = 4.4 Hz). H NMR (CDCl3): δ 2.25 (s, 3H,
3
4
C6H3CH3), 2.64 (s, 6H, N(CH3)2), 7.06 (dd, 1H, JHH = 8.3 Hz, JHP
= 5.0 Hz, arene CH), 7.13 (dd, 1H, JHH = 8.3 Hz, JHH = 1.8 Hz,
3
4
3
4
arene CH), 7.35 (dd, 1H, JHP = 13.4 Hz, JHH = 1.8 Hz, arene CH),
7.46−8.00 (m, 10H, phosphirene Ph). 13C NMR (CDCl3): δ 21.24 (s,
3
2
C6H3CH3), 46.82 (s, N(CH3)2), 120.90 (d, JCP = 5.0 Hz, arene C),
= 8.8 Hz, cis-CO), 197.71 (d, JCP = 32.6 Hz, trans-CO). Anal. Calcd
2
128.80 (d, JCP = 7.2 Hz, ipso-Ph), 129.34 (s, Ph), 129.75 (s, Ph),
for C23H13O5PSW: C, 44.83; H, 2.13. Found: C, 45.42; H, 2.84.
g. Synthesis of [W(CO)5{P(2-C4H3O)C(Ph)C(Ph)}] (10). A solution
of [W(CO)5{P(OSO2CF3)C(Ph)C(Ph)}] (3) was prepared from
[W(CO)5{P(Cl)C(Ph)C(Ph)}] (1, 50.0 mg, 0.088 mmol) and
AgOSO2CF3 (22.6 mg, 0.088 mmol) in CH2Cl2 (5 mL) as described
above. Furan (20 μL, 0.275 mmol) was then added, resulting in an
3
129.81 (s, Ph), 130.43 (s, Ph), 131.98 (d, JCP = 9.4 Hz, arene C),
132.51 (d, 4JCP = 1.7 Hz, arene C), 133.29 (d, 2JCP = 9.4 Hz, arene C),
3
1
134.16 (d, JCP = 8.8 Hz, arene C), 137.06 (d, JCP = 10.0 Hz,
2
phosphirene ring C), 154.14 (d, JCP = 8.8 Hz, arene C), 196.98 (d,
2JCP = 8.8 Hz, JCW = 126.1 Hz, cis-CO), 199.13 (d, JCP = 30.9 Hz,
1
2
F
dx.doi.org/10.1021/om401050w | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
immediate color change to yellow. The solvent was removed under
reduced pressure, and the residue was purified by flash chromatog-
raphy (silica, 20/80 v/v diethyl ether/petroleum ether). Yield: 33 mg,
63%. IR (νCO, CH2Cl2, cm−1): 2076(w), 1944(vs). 31P NMR
(CDCl3): δ −178.6 (s, 1JPW = 280 Hz). 1H NMR (CDCl3): δ 6.40 (m,
1H, PC4H3O), 6.79 (m, 1H, C4H3O), 7.50−7.91 (m, 11H, 10H of Ph
and 1H of C4H3O). 13C NMR (CDCl3): δ 111.56 (d, JCP = 6.5 Hz,
C4H3O), 120.23 (d, JCP = 17.8 Hz, C4H3O), 126.80 (d, J = 7.4 Hz,
NMR (CDCl3): δ −172.5 (d, 1JPW = 271 Hz, 3JPH = 4.4 Hz). 1H NMR
(CDCl3): δ 6.90 (m, 1H, C8H5NH), 7.13 (m, 1H, C8H5NH), 7.35 (m,
2H, C8H5NH), 7.45−7.58 (m, 6H, Ph), 7.72 (m, 1H, C8H5NH), 7.91
− 7.96 (m, 4H, Ph), 8.46 (br s, 1H, C8H5NH). 13C NMR (CDCl3): δ
111.52 (d, 1JCP = 17.0 Hz, C3), 111.86 (s, C7), 120.66 (d, JCP = 1.7 Hz,
2
C4), 121.48 (s, C6), 123.24 (s, C5), 127.89 (s, C3a), 128.81 (d, JCP
=
6.2 Hz, ipso-Ph), 129.51 (s, Ph), 130.33 (s, Ph), 130.41 (s, Ph), 130.53
(s, C2), 130.64 (s, Ph), 135.65 (d, 1JCP = 39.0 Hz, phosphirene ring C),
2
1
137.29 (d, JCP = 6.2 Hz, C7a), 196.70 (d, JCP = 9.1 Hz, JCW = 125.4
2
phosphirene ring C), 127.26 (d, JCP = 6.4 Hz, ipso-Ph), 129.52 (s,
2
1
Hz, cis-CO), 198.45 (d, JCP = 30.0 Hz, trans-CO). Anal. Calcd for
Ph), 130.53 (s, Ph), 130.61 (s, Ph), 130.90 (s, Ph),147.50 (d, JCP
=
=
3.5 Hz, C4H3O), 152.83 (d, JCP = 10.8 Hz, C4H3O), 195.73 (d, 2JCP
C27H16NO5PW: C, 49.95; H, 2.48; N, 2.16. Found: C, 49.45; H, 2.55;
N, 2.21.
8.9 Hz, cis-CO), 197.70 (d, 2JCP = 33.2 Hz, trans-CO). Anal. Calcd for
C23H13O6PW: C, 46.03; H, 2.18. Found: C, 46.27; H, 2.63.
h. Synthesis of [W(CO)5{P{3-C4H(2,5-CH3)2O}C(Ph)C(Ph)}] (11). A
solution of [W(CO)5{P(OSO2CF3)C(Ph)C(Ph)}] (3) was prepared
from [W(CO)5{P(Cl)C(Ph)C(Ph)}] (1, 60.0 mg, 0.106 mmol) and
AgOSO2CF3 (27.1 mg, 0.106 mmol) in CH2Cl2 (4 mL) as described
above. 2,5-Dimethylfuran (23 μL, 0.213 mmol) was then added, and
the solution was stirred for 15 min, resulting in a color change to red.
Triethylamine (15 μL, 0.108 mmol) was then added, resulting in a
color change to yellow. The solvent was removed under reduced
pressure, and the residue was extracted into pentane (5 mL × 2). The
extracts were combined and filtered, and the solvent was removed
under reduced pressure. Yield: 25 mg, 74%. Attempts to purify 11 by
chromatography or recrystallization led to its transformation into the
known hydroxyphosphirene complex [W(CO)5{P(OH)C(Ph)C-
(Ph)}].15 As a result, satisfactory elemental analysis could not be
obtained. IR (νCO, CH2Cl2, cm−1): 2073(w), 1940(vs). 31P NMR
k. Synthesis of [{W(CO)5}2-μ-{C8H5N-1,3-{PC(Ph)C(Ph)}2}] (14). A
solution of [W(CO)5{P(OSO2CF3)C(Ph)C(Ph)}] (3) was prepared
from [W(CO)5{P(Cl)C(Ph)C(Ph)}] (1, 60.0 mg, 0.106 mmol) and
AgOSO2CF3 (27.2 mg, 0.106 mmol) in CH2Cl2 (4 mL) as described
above. This solution was added rapidly to a solution of indole (6.2 mg,
0.053 mmol, 0.5 equivalent vs 1) in CH2Cl2, resulting in a color
change to yellow. To this solution was added triethylamine (15 μL,
0.108 mmol). 31P NMR of the reaction mixture showed 14 to be the
major product, while 13 is still present as a minor product. The solvent
was removed in vacuo, and the residue was purified by flash
chromatography with silica gel (20/80 v/v diethyl ether/petroleum
ether). The yellow product was crystallized by cooling a saturated
CH2Cl2/pentane solution to −20 °C. Yield: 31 mg, 25%. IR (νCO,
CH2Cl2, cm−1): 2076(w), 1944(vs). 31P NMR (CDCl3): δ −129.8 (s,
1
3
1
(CDCl3): δ −181.6 (d, JPW = 273 Hz, JPH = 2.3 Hz). H NMR
(CDCl3): δ 2.16 (s, 3H, CH3), 2.25 (s, 3H, CH3), 5.95 (d, 1H, 3JHP
=
1.8 Hz, PC4HO(CH3)2), 7.48−7.93 (m, 10H, Ph). 13C NMR
2
(CDCl3): δ 13.41 (s, CH3), 13.97 (s, CH3), 109.31 (d, JCP = 15.9
1
Hz, C4HO(CH3)2), 117.31 (d, JCP = 14.3 Hz, C4HO(CH3)2), 128.11
(d,2 JCP = 6.9 Hz, ipso-Ph), 129.58 (s, Ph), 130.19 (d, JCP = 8.9 Hz,
1
phosphirene ring C), 130.32 (s, Ph), 130.40 (s, Ph), 130.78 (s, Ph),
3
2
150.11 (d, JCP = 11.9 Hz, C4HO(CH3)2), 153.94 (d, JCP = 13.4 Hz,
1
3
1JPW = 314 Hz, N-bound P nuclei), −173.8 (d, JPW = 274 Hz, JPH
=
2
2
C4HO(CH3)2), 196.42 (d, JCP = 8.5 Hz, cis-CO), 198.34 (d, JCP
30.7 Hz, trans-CO).
=
2.8 Hz, C bound P nuclei). 1H NMR (CDCl3): δ 6.88 (m, 1H,
C8H5N), 7.12 (m, 1H, C8H5N), 7.25 (d, 1H, JHH = 7.8 Hz, C8H5N),
7.42−7.54 (m, 6H, Ph), 7.58−7.68 (m, 6H, Ph), 7.73 (d, 1H, JHH = 8.4
Hz, C8H5N), 7.78 (t, 1H, JHH = 5.1 Hz, C8H5N), 7.84−7.87 (m, 4H,
i. Synthesis of [W(CO)5{P(2-C4H3NH)C(Ph)C(Ph)}] (12). A solution
of [W(CO)5{P(OSO2CF3)C(Ph)C(Ph)}] (3) was prepared from
[W(CO)5{P(Cl)C(Ph)C(Ph)}] (1, 70.0 mg, 0.123 mmol) and
AgOSO2CF3 (31.6 mg, 0.123 mmol) in CH2Cl2 (5 mL) as described
above. Pyrrole (34 μL, 0.492 mmol) was then added, resulting in a
color change to brown. The solvent was removed under reduced
pressure, and the residue was purified by flash chromatography (silica,
50/50 v/v diethyl ether/petroleum ether). The yellow product was
crystallized by cooling a saturated pentane solution to −20 °C. Yield:
52 mg, 81%. IR (νCO, CH2Cl2, cm−1): 2072(w), 1939(vs). 31P NMR
(CDCl3): δ −174.6 (s, 1JPW = 270 Hz). 1H NMR (CDCl3): δ 6.07 (m,
1H, C4H3NH), 6.75 (m, 1H, C4H3NH), 7.08 (m, 1H, C4H3NH),
7.44−7.91 (m, 10H, Ph), 8.41 (br s, 1H, NH). 13C NMR (CDCl3): δ
Ph), 8.03−8.06 (m, 4H, Ph). 13C NMR (CDCl3): δ 113.00 (d, JCP
=
3.8 Hz, C8H5N), 121.18 (s, C8H5N), 122.48 (s, C8H5N), 123.93 (s,
2
2
C8H5N), 126.70 (d, JCP = 6.2 Hz, ipso-Ph), 128.45 (d, JCP = 6.3 Hz,
ipso-Ph), 129.50 (s, Ph), 129.99 (s, Ph), 130.33 (s, Ph), 130.38 (s, Ph),
130.41 (s, Ph), 130.46 (s, Ph), 130.74 (s, Ph), 131.96 (s, Ph), 138.49
(s, C8H5N), 138.59 (d, JCP = 1.5 Hz, C8H5N), 138.72 (d, JCP = 5.6
2
Hz), 138.81 (s, C8H5N), 139.28 (d, JCP = 5.5 Hz), 194.88 (d, JCP
=
=
2
2
8.5 Hz, cis-CO), 196.29 (d, JCP = 9.1 Hz, cis-CO), 197.24 (d, JCP
40.2 Hz, trans-CO), 198.16 (d, 2JCP = 31.1 Hz, trans-CO). Anal. Calcd
for C46H25NO10P2W2: C, 46.77; H, 2.13; N, 1.19. Found: C, 47.51; H,
2.26; N, 1.52.
3
2
111.43 (d, JCP = 7.8 Hz, C4H3NH), 119.70 (d, JCP = 12.8 Hz,
1
1
l. Synthesis of [W(CO)5{P(OPh)C(Ph)C(Ph)}] (15). A solution of
[W(CO)5{P(OSO2CF3)C(Ph)C(Ph)}] (3) was prepared from [W-
(CO)5{P(Cl)C(Ph)C(Ph)}] (1, 50.0 mg, 0.088 mmol) and
AgOSO2CF3 (22.6 mg, 0.088 mmol) in CH2Cl2 (4 mL) as described
above and added to a solution of phenol (8.3 mg, 0.088 mmol) in
CH2Cl2 (2 mL), resulting in a color change to yellow. The solvent was
removed under reduced pressure, and the residue was purified by flash
chromatography (alumina, 10/90 v/v diethyl ether/petroleum ether).
The pale yellow product was crystallized by cooling a saturated
pentane solution to −20 °C. Yield: 48 mg, 87%. IR (νCO, CH2Cl2,
cm−1): 2078(w), 1947(vs). 31P NMR (CDCl3): δ −67.2 (s, 1JPW = 328
C4H3NH), 120.25 (d, JCP = 21.4 Hz, C4H3NH), 125.98 (d, JCP
=
4
30.0 Hz, phosphirene ring C), 128.02 (d, JCP = 6.2 Hz, C4H3NH),
2
129.18 (d, JCP = 7.3 Hz, ipso-Ph), 129.41 (s, Ph), 130.41 (s, Ph),
130.46 (s, Ph), 130.48 (s, Ph), 196.58 (d, JCP = 9.0 Hz, 1JCW = 125.5
2
2
Hz, cis-CO), 198.54 (d, JCP = 30.0 Hz, trans-CO). Anal. Calcd for
C23H14NO5PW: C, 46.10; H, 2.36; N, 2.34. Found: C, 46.13; H, 2.32;
N, 2.33.
j. Synthesis of [W(CO)5{P(3-C8H5NH)C(Ph)C(Ph)}] (13). A solution
of [W(CO)5{P(OSO2CF3)C(Ph)C(Ph)}] (3) was prepared from
[W(CO)5{P(Cl)C(Ph)C(Ph)}] (1, 70.0 mg, 0.123 mmol) and
AgOSO2CF3 (31.6 mg, 0.123 mmol) in CH2Cl2 (5 mL) as described
above and added dropwise to a solution of indole (14.4 mg, 0.123
mmol) in CH2Cl2 (2 mL), resulting in a color change to yellow. The
solvent was removed under reduced pressure, and the residue was
purified by flash chromatography (alumina, 50/45/5 v/v/v diethyl
ether/petroleum ether/methanol). The yellow product was crystal-
lized by cooling a saturated CH2Cl2/pentane solution to −20 °C.
Yield: 58 mg, 73%. IR (νCO, CH2Cl2, cm−1): 2072(w), 1938(vs). 31P
1
Hz). H NMR (CDCl3): δ 6.79 (m, 2H, OPh), 6.97 (m, 1H, OPh),
7.09 (m, 2H, OPh), 7.47−7.84 (m, 10H, Ph). 13C NMR (CDCl3): δ
3
4
122.27 (d, JCP = 4.6 Hz, OPh), 124.77 (d, JCP = 2.3 Hz, OPh),
128.07 (d, 2JCP = 4.0 Hz, ipso-Ph), 129.48 (s, Ph), 129.79 (d, 5JCP = 1.7
Hz, OPh), 129.87 (s, Ph), 129.94 (s, Ph), 131.22 (s, Ph), 145.73 (d,
1JCP = 17.3 Hz, phosphirene ring C), 151.85 (d, JCP = 13.2 Hz, ipso-
2
OPh), 195.34 (d, 2JCP = 9.7 Hz, JCW = 125.5 Hz, cis-CO), 198.56 (d,
1
G
dx.doi.org/10.1021/om401050w | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
2JCP = 41.5 Hz, trans-CO). Anal. Calcd for C25H15O6PW: C, 47.95; H,
2.41. Found: C, 48.39; H, 2.54.
(DFT), with the B3LYP exchange−correlation functional,21 as
implemented in the Gaussian 09 (revision C. 01) software package.22
Basis set LANL2DZ was used for W, and 6-31G(d,p) was used for all
other atoms (C, H, O, and P). The nature of the optimized structures
was identified from the vibrational frequency analysis. Gaussion 09 was
also used for computing the NBO charges.23 The keywords used in the
input files were # opt freq=noraman rb3lyp pop=(npa) gen pseudo=read.
m. Synthesis of [W(CO)5{P(NPh2)C(Ph)C(Ph)}] (16). A solution of
[W(CO)5{P(OSO2CF3)C(Ph)C(Ph)}] (3) was prepared from [W-
(CO)5{P(Cl)C(Ph)C(Ph)}] (1, 50.0 mg, 0.088 mmol) and
AgOSO2CF3 (22.6 mg, 0.088 mmol) in CH2Cl2 (4 mL) as described
above and added to a solution of diphenylamine (29.8 mg, 0.176
mmol) in CH2Cl2 (3 mL), resulting in a color change to yellow. The
solvent was removed under reduced pressure, and the residue was
purified by flash chromatography (alumina, 10/90 v/v diethyl ether/
petroleum ether). The yellow product was crystallized by cooling the
saturated pentane solution to −20 °C. Yield: 57 mg, 92%. IR (νCO,
CH2Cl2, cm−1): 2074(w), 1942(vs). 31P NMR (CDCl3): δ −108.3 (s,
1JPW = 310 Hz). 1H NMR (CDCl3): δ 6.96−7.06 (m, 6H, phosphirene
ring Ph), 7.12−7.17 (m, 4H, N(Ph)2), 7.34−7.44 (m, 6H, N(Ph)2),
ASSOCIATED CONTENT
* Supporting Information
■
S
NMR spectra for compounds 11, 18, and 19. Optimized
structures with NBO charges, numbers of imaginary
frequencies, absolute energies, and Cartesian coordinates. CIF
files containing crystallographic data for 5, 7, and 9. This
material is available free of charge via the Internet at http://
pubs.acs.org.
7.59−7.63 (m, 4H, phosphirene ring Ph). 13C NMR (CDCl3): δ
2
125.10 (s, NPh), 126.53 (s, NPh), 126.59 (s, NPh), 128.07 (d, JCP
=
5.1 Hz, ipso-Ph), 129.28 (s, Ph), 129.34 (s, Ph), 129.69 (s, Ph), 130.56
(s, Ph), 140.46 (d, 2JCP = 14.6 Hz, phosphirene ring C), 144.04 (d, 2JCP
AUTHOR INFORMATION
Corresponding Author
*E-mail: brian.sterenberg@uregina.ca.
■
2
1
= 2.8 Hz, ipso-NPh), 196.10 (d, JCP = 9.1 Hz, JCW = 125.6 Hz, cis-
2
1
CO), 198.59 (d, JCP = 37.7 Hz, JCW = 149.8 Hz, trans-CO). Anal.
Calcd for C31H20NO5PW: C, 53.09; H, 2.87; N, 2.00. Found: C, 52.98;
H, 2.94; N, 2.09.
Notes
n. Synthesis of [W(CO)3(I)2{P(2-C6H3(2-N(CH3)2)(5-CH3))C(Ph)C-
(Ph)-κ2P,N}] (18). Compound 6 (60 mg, 0.090 mmol) was dissolved in
CH2Cl2 (3 mL). A solution of iodine (22.8 mg, 0.090 mmol) in
CH2Cl2 (5 mL) was added dropwise, resulting in a color change to
dark yellow. The solvent was removed under reduced pressure, and the
residue was washed with pentane. Compound 18 decomposes in
solution, so further purification was not possible, and the crude
product was used in the subsequent reaction. Yield: 72 mg, 93%. IR
(νCO, CH2Cl2, cm−1): 2034(m), 1958(s), 1917(m). 31P NMR
(CDCl3): δ −100.7 (dd, JPW = 247 Hz, JPH = 13.4 Hz, JPH = 6.0
Hz). 1H NMR (CDCl3): δ 2.25 (s, 3H, C6H3CH3), 3.74 (s, 6H,
N(CH3)2), 6.90 (m, 1H, arene CH), 7.34 (m, 1H, arene CH), 7.50−
8.01 (m, 11H, 10H of Ph and 1H of arene).
o. Synthesis of P{2-C6H3(2-N(CH3)2)(5-CH3)}C(Ph)C(Ph) (19).
Compound 18 (72 mg, 0.083 mmol) was dissolved in CH2Cl2 (5
mL). A solution of 2,2′-bipyridine (13.0 mg, 0.083 mmol) in CH2Cl2
(2 mL) was added, and the resulting solution was stirred for 16 h. The
solution color changed from yellow to brown, and an orange
precipitate was formed. The solvent was removed under reduced
pressure, and the residue was purified by flash chromatography
(alumina, 5/95 v/v ethylacetate/pentane). Yield: 21 mg, 73%. As a free
ligand, 19 is thermally unstable and decomposes over time in the solid
state or in solution. As a result, satisfactory elemental analysis could
not be obtained. 31P NMR (CDCl3): δ −190.7 (s). 1H NMR
(CDCl3): δ 1.97 (s, 3H, C6H3CH3), 2.88 (s, 6H, N(CH3)2), 6.67 (m,
1H, arene CH), 6.89 (m, 2H, arene CH), 7.29−7.83 (m, 10H, Ph).
13C NMR (CDCl3): δ 21.06 (s, CH3), 46.74 (s, N(CH3)2), 118.84 (s,
Ar), 123.47 (d, 2JCP = 46 Hz, ipso-Ph), 127.0 (d, 1JCP = 32 Hz, ipso-Ar),
129.01 (s, Ph), 129.27 (s, Ph), 129.99 (s, Ar), 130.82 (s, Ph), 131.68
(d, 1JCP = 20 Hz, phosphirene ring C), 132.22 (s, Ar), 132.70 (s, ipso-
Ar), 155.2 (s, ipso-Ar).
X-ray Crystallography. Suitable crystals of compounds 5, 7, and 9
were mounted on glass fibers. Programs for diffractometer operation,
data collection, cell indexing, data reduction, and absorption correction
were those supplied by Bruker AXS Inc., Madison, WI. Diffraction
measurements were made on a PLATFORM diffractometer/SMART
1000 CCD using graphite-monochromated Mo Kα radiation at −80
°C. The unit cell was determined from randomly selected reflections
obtained using the SMART CCD automatic search, center, index, and
least-squares routines. Integration was carried out using the program
SAINT, and an absorption correction was performed using SADABS.
Structure solution was carried out using the SHELX9719 suite of
programs and the WinGX graphical interface.20 Initial solutions were
obtained by direct methods and refined by successive least-squares
cycles. All non-hydrogen atoms were refined anisotropically.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We thank Bob McDonald and Mike Ferguson (University of
Alberta) for X-ray data collection, Compute Canada (West-
Grid) for computing resources, and the University of Regina for
funding.
1
3
4
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dx.doi.org/10.1021/om401050w | Organometallics XXXX, XXX, XXX−XXX