Synthesis and reactions of the first room temperature stable Li/Cl phosphinidenoid complex

Article abstract of DOI:10.1021/ic301652u

P-Trityl substituted Li/Cl phosphinidenoid tungsten(0) complex (OC) ₅W{Ph₃CP(Li/12-crown-4)Cl} (3) was prepared via chlorine/lithium exchange in complex (OC)₅W{Ph₃CPCl ₂} (2) using ^tBuLi in the presence of 12-crown-4 in tetrahydrofuran (THF) at low temperature; complex 3 possesses significantly increased thermal stability in contrast to previously reported analogue derivatives. Terminal phosphinidene-like reactivity of 3 was used in reactions with benzaldehyde and isopropyl alcohol as oxaphosphirane complex (OC) ₅W{Ph₃CPC(Ph)O} (5) and phosphinite complex (OC) ₅W{Ph₃CP(H)OⁱPr} (6) were obtained selectively. Reaction of 3 with phosgene allowed to obtain the first kinetically stabilized chloroformylphosphane complex (OC)₅W{Ph₃CP(Cl)C(O)Cl} (4). Density functional theory (DFT) calculations revealed remarkable differences in the degree of P-Li bond dissociation 3a-d: using a continuum model 3 displays a covalent character of P-Li bond (COSMO (THF)) (a), which becomes elongated if 12-crown-4 is coordinated to lithium (b) and is cleaved if a dimethylether unit is additionally coordinated to lithium (c). A similar result was obtained for the case of 3(thf)₄ in which also a solvent-separated ion pair structure is present (d). All products were unambiguously characterized by various spectroscopic means and, in the case of 2 and 4-6, by single-crystal X-ray diffraction analysis. In all structures very long P-C bonds were determined being in the range from 1.896 to 1.955 .

Full text of DOI:10.1021/ic301652u

Article
pubs.acs.org/IC
Synthesis and Reactions of the First Room Temperature Stable Li/Cl
Phosphinidenoid Complex
Vitaly Nesterov,† Gregor Schnakenburg,† Arturo Espinosa,‡ and Rainer Streubel*,†
†Institut fur Anorganische Chemie, Rheinischen Friedrich-Wilhelms-Universitat Bonn, Gerhard-Domagk-Strasse 1, 53121 Bonn,
̈
̈
Germany
‡Departamento de Química Organ
́
ica, Facultad de Química, Universidad de Murcia, Campus de Espinardo, 30100 Murcia, Spain
S
* Supporting Information
ABSTRACT: P-Trityl substituted Li/Cl phosphinidenoid
tungsten(0) complex (OC)5W{Ph3CP(Li/12-crown-4)Cl}
(3) was prepared via chlorine/lithium exchange in complex
t
(OC)5W{Ph3CPCl2} (2) using BuLi in the presence of 12-
crown-4 in tetrahydrofuran (THF) at low temperature;
complex 3 possesses significantly increased thermal stability
in contrast to previously reported analogue derivatives.
Terminal phosphinidene-like reactivity of 3 was used in
reactions with benzaldehyde and isopropyl alcohol as
oxaphosphirane complex (OC)5W{Ph3CPC(Ph)O} (5) and
phosphinite complex (OC)5W{Ph3CP(H)OiPr} (6) were
obtained selectively. Reaction of 3 with phosgene allowed to
obtain the first kinetically stabilized chloroformylphosphane complex (OC)5W{Ph3CP(Cl)C(O)Cl} (4). Density functional
theory (DFT) calculations revealed remarkable differences in the degree of P−Li bond dissociation 3a−d: using a continuum
model 3 displays a covalent character of P−Li bond (COSMO (THF)) (a), which becomes elongated if 12-crown-4 is
coordinated to lithium (b) and is cleaved if a dimethylether unit is additionally coordinated to lithium (c). A similar result was
obtained for the case of 3(thf)4 in which also a solvent-separated ion pair structure is present (d). All products were
unambiguously characterized by various spectroscopic means and, in the case of 2 and 4−6, by single-crystal X-ray diffraction
analysis. In all structures very long P−C bonds were determined being in the range from 1.896 to 1.955 Å.
reported (R = CH(SiMe3)21aand Cp*1b) that decompose
INTRODUCTION
■
around −45 to −30 °C, and which enabled access to various
classes of compounds under very mild conditions.6 Formal
exchange of the substituent X at phosphorus, for example,
halogen vs alkoxide,3 led to a significant change in reactivity and
stability, that is, a phosphanido complex reactivity came to the
fore. Somehow similar is that exchange of lithium for bulky,
“non-coordinating organic cations” in complexes I (X = F, Cl,
OMe, OPh)8 significantly increased their thermal stability, but
the terminal phosphinidene complex-like reactivity9 of the
phosphinidenoid complexes was no longer observed. Therefore,
the challenge to synthesize room temperature-stable derivatives
I while keeping this specific and synthetically important
reactivity remained.
Phosphinidenoid complexes I represent a new unique class of
transition-metal coordination compounds possessing unusual
(formal) anionic P-ligands with dicoordinate phosphorus atoms
having a bulky organic substituent and an electron-withdrawing
group such as a halogen,1 cyano,2 alkoxide,3 or amide.4 During
the past years a close relationship to the chemistry of
carbenoids II5 (Scheme 1) emerged as complexes I display
terminal phosphinidene complex-like and nucleophilic reac-
tivity.6 In contrast to I, unligated phosphinidenoids III are still
unknown, although some evidence for their transient formation
has been reported.7 So far, only two thermally labile Li/Cl
phosphinidenoid tungsten(0) complex derivatives have been
Kinetic stabilization of reactive molecular species through
sterically demanding substituents bound to the reactive site (or
a neighboring atom) is a well-documented strategy in reactive
intermediate chemistry,10 in general, and in organophosphorus
chemistry in particular.11 The bulkiness of the triphenylmethyl
group (“trityl”) combined with its intrinsic abilities to stabilize a
negative and/or positive charge, or even a radical center makes
Scheme 1. Phosphinidenoid Complexes I, Carbenoids II,
and Phosphinidenoids III
a
a
MLn = transition-metal complex; R, R′ = organic moieties, X =
Received: July 27, 2012
electronegative atom or group.
© XXXX American Chemical Society
A
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Scheme 2. Synthesis of Li/Cl Phosphinidenoid Complex 3 from Complex 2
the trityl group unique and has attracted interest from various
angles since the early and fundamental work of Gomberg.12
Schmutzler was first to demonstrate that the trityl group can be
used in molecular phosphorus chemistry to great advantage13
and to access a wide variety of very reactive and/or unstable
compounds, for example, acyclic diphospha-urea derivatives,14
1,3-diphosphetane-2,4-dione, and acyl(chloro)-
organophosphanes,15 and more.16 Grutzmacher recognized
̈
the synthetic potential for low-coordinate phosphorus com-
pounds and reported on the synthesis and reactivity of C-
tritylphosphaalkyne.17 It was again Schmutzler who found that
trityl can serve as a leaving group,18 but in this case only
preliminary work was done; recent computational studies
stressed the reactivity-determining key role of P-trityl groups in
three-membered phosphorus heterocycles.19 To date, only few
coordination compounds of P-trityl substituted phosphane
complexes have been reported.20 Recently, we came into this
field through the discovery that coupling between a trityl and
sterically demanding P-functional phosphanyl complexes can
occur to form a P−C bond either in the trityl periphery21a or,
after a series of rearrangements, at the tertiary carbon of the
trityl moiety, if the para-position was blocked by a methyl
group.21b
Figure 1. Molecular structure of complex 2 in the crystal (50%
probability level, hydrogen atoms are omitted for clarity). Selected
bond lengths [Å] and angles [deg]: W−P 2.4685(6), P−C(1)
1.955(2), P−Cl(1) 2.043(8), P−Cl(2) 2.063(8); C(1)−P−W
129.16(7), Cl(1)−P−Cl(2) 99.89(3), Cl(1)−P−C(1) 102.46(7),
Cl(2)−P−C(1)101.80(7).
by an immediate color change of the reaction mixture from
colorless to dark-yellow. In the 31P{1H} NMR spectrum (THF-
d8) complex 3 displays a signal at 252.1 ppm with a
phosphorus−tungsten coupling constant of 77.6 Hz (cf. 2: δP
= 166.2 ppm, 1JP,W = 319.7 Hz); this signal displayed a shoulder
on the high-field side (ratio of ca. 3:1) that corresponds to the
37Cl isotopomer of 3. Meanwhile, such 31P NMR data are
characteristic features for the class of phosphinidenoid
Herein, we report the synthesis and reactions of the P-trityl
substituted Li/Cl phosphinidenoid tungsten(0) complex, the
first derivative to be stable in tetrahydrofuran (THF) solution
at ambient temperature, while retaining the combined
nucleophilic and terminal phosphinidene complex-like reac-
tivity.
7
complexes. The Li NMR spectrum of 3 contains a sharp
signal at −0.32 ppm, and no phosphorus−lithium coupling was
observed between +25 and −60 °C. On the basis of DOSY
NMR experiments on a related Li/F phosphinidenoid complex
[(OC)5W{(Me3Si)2CHP(Li/12-crown-4)F}),25 it is estab-
lished that the constitution of the species is that of solvent
separated ion pairs and, therefore, the same is assumed for the
present case of 3. Remarkably, phosphinidenoid complex 3 is
stable for many hours at 25 °C in THF solution (half-lifetime is
about 12 h) and, notably, less than 30% of 3 decomposed after
2 h at 45 °C. In contrast to previously reported Li/Cl
phosphinidenoid complexes, derivative 3 could be isolated as a
yellow, highly moisture sensitive solid. Despite much effort, no
single-crystals of 3 suitable for X-ray diffraction analysis were
obtained, unfortunately.
Surprisingly, the thermal decomposition of complex 3 in
THF at 25 °C, monitored by 31P NMR spectroscopy, led to a
complicated, inseparable mixture of products, from which only
the signal at −41.2 ppm (tSat, 1JP,H= 329.3 Hz, 1JP,W = 225.1 Hz)
could be assigned to the primary phosphane complex
[(OC)5W(Ph3CPH2)]. Surprisingly, no evidence for the
formation of mono- or dinuclear P-trityl diphosphene
complexes or the terminal phosphinidene complex was
obtained, as it was expected in analogy to the case of P-
bis(trimethylsilyl)methyl substituted Li/X phosphinidenoid
complexes.1a,c
RESULTS AND DISCUSSION
■
The first hurdle to obtain the coordination compound as
starting material could be overcome, and complex 2 was
prepared via selective reaction of dichloro(triphenylmethyl)-
phosphane 113 with acetonitrile (pentacarbonyl)tungsten(0)22
(Scheme 2). It should be noted that under these conditions
only approximately 75% conversion of the starting phosphane 1
was achieved which could not be increased further by heating
or addition of slight excess of the acetonitrile tungsten
complex.23 Complex 2 was obtained in 65% yield after column
chromatography.
The composition of complex 2 was unambiguously
confirmed by single-crystal X-ray diffraction analysis (Figure
1); for further information on crystallographic parameters of 2
as well as 4−6 see the Supporting Information. The molecular
structure of 2 possesses a very long P−C bond of 1.955(2) Å
(the sum of covalent radii of P and C atoms is 1.83 Å), which is
significantly longer compared with that of the unligated
phosphane 1 (1.9333(14) Å).13,24
Chlorine/lithium exchange in dichlorophosphane complex 2
was achieved with tBuLi in the presence of 12-crown-4 in THF
at low temperature (−78 °C), which led to the quantitative
formation of the corresponding Li/Cl phosphinidenoid
complex 3 (Scheme 2). Formation of complex 3 is fast at
−78 °C (completion in less than 20 min) and is accompanied
Because of the extraordinary thermal stability of 3, it was
tempting to probe if a phosphinidenoid complex could be
B
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Figure 2. Calculated (COSMOTHF/B3LYP-D/def2-TZVP ecp) minimum energy structures for (a) complex 3 and its solvates with (b) 12-c-4, (c)
12-c-4 and Me2O, and (d) four THF molecules. W, ice blue; P, orange; Cl, green; Li, purple.26
obtained without 12-crown-4, especially as it was not achieved
before in the case of other Li/Cl phosphinidenoid derivatives
(R = C5Me5 or CH(SiMe3)2). Therefore, complex 2 was
Table 1. Selected Calculated Parameters Related to the
Extent of P−Li Bond Dissociation in Solvates of 3
a
dP···Li [Å]
qP/P[W] [au]
t
treated with BuLi in the absence of 12-crown-4 in THF at low
3
2.462
2.765
4.701
5.260
0.33/−0.27
0.33/−0.31
0.34/ −0.45
0.27/−0.45
temperature (−78 °C) which yielded a product that displayed
nearly the same 31P NMR data as complex 3, that is, 253.5 ppm
(1JP,W = 76.3 Hz), being also stable in solution and thus
revealing that the presence of 12-crown-4 is not a conditio sine
qua non for Li/Cl phosphinidenoid complexes.
3·(12-c-4)
3·(12-c-4)(OMe2)
3·(THF)4
a
Lowdin atomic charge at P and at the PW(CO) moiety.
̈
5
To unravel the unprecedent dispensability of 12-crown-4
(12-c-4 for short) and to get further structural insight into the
molecular structure of 3 in solution a quantum chemical
calculation at the DFT (COSMOTHF/B3LYP-D/def2-TZVP,
ECP for W) level was performed. Therefore, four differently
solvated species were considered: the nonexplicitly solvated
entity (without 12-crown-4 or any coordinating solvent
molecule) (a), two derivatives including a 12-c-4 moiety
without (b) and with a dimethyl ether unit (c) (the latter as a
model for THF) and, last, one containing four explicit
molecules of THF (d) (Figure 2).
Inspection of the resulting geometries revealed remarkable
differences of the degree of P−Li bond dissociation. Structure a
of 3 (without 12-c-4) shows a mainly covalent, short P−Li
bond (Table 1), even if computed using a continuum model
(COSMOTHF).27 This results in a relatively low ionic character
of the bond, as shown by the low negative electric charge at the
PW(CO)5 moiety. If a 12-c-4 unit is bound to Li (b) the P−Li
bond is not significantly elongated unless a THF molecule
(Me2O as model) is coordinated (c). This in turn leads to P−Li
bond elongation and the emergence of notable negative charge
at phosphorus and the formation of a coordinated lithium
cation! A very similar behavior is observed when four molecules
of THF coordinate the lithium cation (d) which also produces
a solvent-separated ion pair structure with a remarkably long
P−Li bond distance and, therefore, significant ionic character;
this supports the experimentally observed similarity of the
NMR data for 3 in the absence or presence of 12-c-4.
To investigate the reactivity of Li/Cl phosphinidenoid
complex 3 a set of prototypical aspects were chosen. To obtain
a chloroformylphosphane complex possessing increased ther-
mal stability,28 in situ prepared 3 was reacted with an excess of
phosgene (30% solution in toluene) at −105 °C which was
accompanied by immediate formation of a precipitate and led
selectively to the (chloroformyl)tritylphosphane complex 4
(Scheme 3).
In contrast to known P-functional acyl(organo)phosphane
complexes,6f chloroformyl derivative 4 slowly decomposed in
solution at ambient temperature to give the dichlorophosphane
complex 2 via extrusion of CO;29 at 25 °C the half-lifetime of 4
is about 5 days (benzene).30 Nevertheless, it was possible to
isolate complex 4 in pure form at low temperature (−20 °C) in
quite good yields (ca. 75%).31 Complex 4 was obtained as a
light-yellow solid, being stable under argon atmosphere at −20
°C. In the 31P NMR spectrum the signal of complex 4 appeared
at 148.6 ppm (1JP,W = 278.5 Hz). The signal of the carbonyl
carbon atom of the chloroformyl substituent was observed as a
doublet (1JC,P = 13.6 Hz) at 176.9 ppm. In the IR spectrum the
absorption band of the carbonyl group of the chloroformyl
C
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Scheme 3. Reaction Li/Cl Phosphinidenoid Complex 3 with Phosgene to Give 4
moiety appeared at 1747 cm−1 which is well distinguished from
Scheme 4. Reactions of Li/Cl Phosphinidenoid Complex 3
with Benzaldehyde and Isopropanol
those of the W(CO)5 unit (1942, 1959, 2078 cm−1).
The molecular structure of the chloroformylphosphane
complex 4 was confirmed by single-crystal X-ray diffraction
studies, thus representing the first-ever structurally charac-
terized molecular compound possessing a ClC(O)P unit
(Figure 3). The two P−C bonds of complex 4 were found to
similar derivatives.32,33 The constitution of the product was
unambiguously confirmed by X-ray diffraction studies (Figure
4).
Figure 3. Molecular structure of complex 4 in the crystal (50%
probability level, hydrogen atoms are omitted for clarity). Selected
bond lengths [Å] and angles [deg]: W−P 2.472(2), P−C(1) 1.899(5),
P−C(2) 1.945(5), P−Cl(1) 2.032(18), C(1)−Cl2 1.783(5), C(1)−
P−Cl(1) 101.19 (17), C(2)−P−Cl(1) 103.36(17), C(1)−P−C(2)
103.0(2), Cl(2)−C(1)−P 116.0(3).
be elongated: P−C(2) 1.945(5) and P−C(1) 1.899(5) Å. The
elongation of P−C(1) in this case is expected, following the
general tendency of P−C bond elongation in acylphosphane
6
complexes.[cf. f]
Figure 4. Molecular structure of oxaphosphirane complex 5 in the
crystal (50% probability level, hydrogen atoms except H(1) are
omitted for clarity). Selected bond lengths [Å] and angles [deg]: W−P
2.482(6), P−O(1) 1.669(16), O(1)−C(1) 1.468(3), C(1)−P
1.788(2), P−C(8) 1.896(2), O(1)−P−C(1) 50.12(9), C(1)−O(1)−
P69.14(11), O(1)−C(1)−P 60.74(10).
To examine the reactivity further, the reaction of Li/Cl
phosphinidenoid complex 3 with benzaldehyde or isopropyl
alcohol was chosen (Scheme 4). Addition of 2 equiv of
benzaldehyde to a solution of freshly prepared 3 (−78 °C) led
to immediate precipitate formation and color change of the
reaction mixture to light-yellow. The selective formation of the
diastereomerically pure oxaphosphirane complex 5 was
confirmed by 31P NMR spectroscopy, and complex 5 was
isolated in pure form as a stable white solid.
The P−C(8) bond in P-trityl oxaphosphirane complex 5
(1.896(2) Å) keeps some elongation but is significantly shorter
than in the P-trityl dichlorophosphane complex 2 although still
longer than P−C bonds in related P-bis(trimethylsilyl)methyl
and P-Cp* oxaphosphirane derivatives (1.794(6) and
1.855(3)).
Under similar conditions, Li/Cl phosphinidenoid complex 3
was then reacted with a 10-fold excess of isopropanol which led
selectively to the isopropylphosphinite complex 6 (Scheme 4).
The product was obtained in good yield (84%) as a white solid
after column chromatography. The 31P NMR signal of complex
The 31P NMR spectrum (C6D6) of 5 showed a signal at 16.0
ppm (1JP,W = 311.5 Hz) which is significantly high-field shifted
compared to those of analogous P-bis(trimethylsilyl)methyl and
P-Cp* oxaphosphirane tungsten(0) complexes (40.4 ppm
(1JP,W = 308.2 Hz) in CDCl3,32 and 31.6 ppm (1JP,W = 309.0
Hz)33 in C6D6). In the 13C NMR spectrum the signal of the
oxaphosphirane ring carbon atom appeared at 60.4 ppm (1JC,P
=
23.6 Hz), which is close to the values reported before for
D
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1
3 was observed at 115.2 ppm (1JP,W = 278.5 Hz; JP,H = 329.3
tendency for P−C bond cleavage processes. Of particular
interest is that a pure crystalline product of a chloroformyl-
phosphane derivative was obtained in good yields (complex 4),
a class of compounds otherwise known to be highly unstable.
Therefore, this P-Cl, C-Cl bifunctional building block may serve
as new starting point and thus open new perspectives in
synthetic organophosphorus chemistry.
3
and JP,H = 8.9 Hz). The single crystal X-ray crystallography
study of 6 revealed also a long P−C bond of 1.913(1) Å
(Figure 5), which is significantly elongated by comparison to
EXPERIMENTAL PART
■
General Procedures. All manipulations involving air- and
moisture sensitive compounds were carried out under an atmosphere
of purified argon by using standard Schlenk-line techniques or in a
glovebox. Solvents were dried with appropriate drying agents such as
sodium-wire/acetophenone and degassed before use. The 1H, 13C-
{1H}, and 31P{1H} NMR spectroscopic data were recorded on a
Bruker DMX 300 spectrometer. MAS NMR: Varian 400 Infinity+, 4
mm MAS NMR triple-resonance probe (25 °C). Infrared spectra were
recorded on a Thermo Nicolet 380 FT-IR spectrometer (selected data
given). Mass spectra were recorded on a MAT 90 Finnigan
spectrometer (selected data given). Melting points were determined
using a Buchi Type S apparatus with samples sealed in capillaries
under argon, and are uncorrected. Elemental analyses were performed
using an ElementarVarioEL instrument.
Figure 5. Molecular structure of isopropylphosphinite complex 6 in
the crystal (50% probability level, hydrogen atoms except H(23) are
omitted for clarity). Selected bond lengths [Å] and angles [deg]: W−P
2.524(7), P−C(1) 1.913(3), P−O(1) 1.608(2), O(1)−P−H(23)
104.2(11), O(1)−P−C(1) 104.77(11), C(1)−P−H(23) 98.1(11).
Synthesis of [(OC)5W{Ph3CPCl2}](2). Dichloro(triphenylmethyl)-
phosphane 113 (3.55 g, 10.3 mmol) dissolved in 25 mL of freshly
distilled THF was added to
a stirred solution of [W-
(CO)5(CH3CN)]22 (3.76 g, 10.3 mmol) in 25 mL of THF. The
reaction mixture was heated at 45 °C for about 64 h while stirring.
After removing of all volatiles in vacuum, the residue was adsorbed on
a small amount of Al2O3, and column chromatography was performed
(Al2O3, −15 °C, eluent: petrol ether/dichloromethane from 10/1 to
10/4). Evaporation of the solvents gave complex 2 as a white
crystalline solid.
complex 5 despite the fact that in this case a less electronegative
and less bulky atom as hydrogen (not carbon) is bound to
phosphorus.
As complex 6 formally represents an insertion product of the
terminal phosphinidene complex [(CO)5W(PCPh3)] into the
O−H bond of isopropanol, a 31P NMR reaction monitoring
was performed. Unfortunately, this only revealed a slow
reaction of the alcohol with complex 3 at low temperature
which became significantly faster above −10 °C. Notably, no
evidence for any P-containing intermediate was obtained in this
reaction of Li/Cl phosphinidenoid complex 3. Therefore, one
may conclude that reaction did not occur via the P-protonated
intermediate, that is, complex 3 was directly converted into the
final product, the isopropylphosphinite complex 6, via an
unknown pathway.
1
Yield: 4.5 g (65%); mp 176 °C (dec.). H NMR (CDCl3): 7.38−
7.49 (15 H, m, CPh3).13C{1H} NMR (CDCl3): 75.5 (d, JC,P = 10.7
1
5
5
Hz, CP), 127.9 (d, JC,P = 1.8 Hz, para-Ph), 128.5 (d, JC,P = 2.1 Hz,
para-Ph), 128.9 (d,4JC,P = 1.9 Hz, meta-Ph), 128.9 (d, JC,P = 3.9 Hz,
4
meta-Ph), 130.9 (d, 3JC,P = 3.8 Hz, ortho-Ph), 131.1 (d, 3JC,P = 8.7 Hz,
ortho-Ph), 140.3 (d, 2JC,P = 6.4 Hz, ipso-Ph), 140.8 (d, 2JC,P = 10.8 Hz,
2
1
ipso-Ph), 195.9 (dSat, JC,P = 7.1 Hz, JC,W = 128.7 Hz, cis-CO), 198.9
2
(d, JC,P = 48.0 Hz, trans-CO). 31P{1H} NMR (CDCl3): 166.2 (sSat,
1JP,W = 319.7 Hz). IR (KBr; υmax/cm−1): 1942 (vs, CO), 1955 (vs,
CO), 2082 (s, CO). Anal. Calcd. for C24H15Cl2O5PW: C, 43.08; H,
2.26. Found: C, 43.13; H, 2.53.
Synthesis of [Li(12-crown-4)(THF)n][(OC)5W{Ph3CPCl}] (3) for
the Spectroscopic Characterization. To a stirred solution of
phosphane complex 2 (67 mg, 0.1 mmol) and 12-crown-4 (17.5 μL,
0.11 mmol) in 0.8 mL of THF-d8 was added dropwise solution of
tBuLi in n-hexane (1.6 M, 0.07 mL) at −78 °C to give a dark-yellow
CONCLUSIONS
■
P-Trityl substituted complex 3 is the first-ever example of a Li/
Cl phosphinidenoid tungsten(0) complex stable for hours in
solution at ambient temperature. It also deserves mention that
P-chloro phosphinidenoid derivatives may exist without 12-
crown-4 if strongly coordinating solvent molecules such as
THF can parallel the cation-interaction of the 12-crown-4 unit.
In general and as shown by DFT calculations, a solvent-
separated ion-pair structure of a P-chloro phosphanido-like
complex having an enhanced P-anionic character is produced in
solution. Perhaps the most notable aspect of this study is that
the enhanced stability of 3 did not necessarily alter the
reactivity as reactions with benzaldehyde or phosgene
demonstrated, yielding complexes 4 and 5, respectively. As
complex 3 reacted with isopropanol to provide complex 6 via
an unknown pathway, the (undetected) terminal phosphini-
dene complex [(CO)5W(PCPh3)] might be involved. Note-
worthy is that all molecular X-ray structures of P-trityl
substituted complexes (2, 4−6) display very long P−C bond
distances in the range from 1.896 to 1.955 Å. This may hint to a
masked functionality of the trityl group, for example, a
solution. After 20 min stirring at −78 °C solution was quickly
transferred via double-needle to a cooled (−90 °C) NMR tube.
3:34 1H NMR (CDCl3, −40 °C): 3.69 (s, 16 H, 12-crown-4), 7.0−
7.65 (15 H, m, CPh3). 13C{1H} NMR (CDCl3, −40 °C): 67.5 (s, 12-
1
crown-4), 68.1(d, JC,P = 13.3 Hz, CP), 125.0 (s, para-Ph), 125.2 (s,
para-Ph), 126.1 (d, 5JC,P = 1.5 Hz, para-Ph), 126.9 (s, meta-Ph), 127.5
3
(s, meta-Ph), 128.4 (s, meta-Ph), 129.9 (d, JC,P = 18.3 Hz, ortho-Ph),
131.9 (s, ortho-Ph), 132.2 (d, 3JC,P = 10.1 Hz, ortho-Ph), 148.7 (d, 2JC,P
2
= 22.2 Hz, ipso-Ph), 149.9 (s, ipso-Ph), 150.6 (d, JC,P = 9.6 Hz, ipso-
2
1
Ph), 202.4 (dSat, JC,P = 7.8 Hz, JC,W = 127.5 Hz, cis-CO), 206.8 (d,
2JC,P =15.0 Hz, trans-CO). 31P{1H} NMR (CDCl3, −40 °C): 252.1
(sSat, 1JP,W = 77.6 Hz) − major, 252.01 (sSat, 1JP,W = 77.6 Hz) − minor.
Synthesis of 3 (without 12-crown-4):34 Prepared analogously,
without using 12-crown-4. 1H NMR (CDCl3, −40 °C): 7.13−7.73 (15
H, m, CPh3). 13C{1H} NMR (CDCl3, −40 °C): 68.1 (d,1JC,P = 12.4
5
Hz, CP), 124.8 (s, para-Ph), 125.1 (s, para-Ph), 125.9 (d, JC,P = 1.5
Hz, para-Ph), 126.8 (s, meta-Ph), 127.4 (s, meta-Ph), 128.3 (s, meta-
Ph), 129.9 (d, 3JC,P = 19.2 Hz, ortho-Ph), 131.9 (s, ortho-Ph), 132.3 (d,
3JC,P = 11.2 Hz, ortho-Ph), 149.0 (d, 2JC,P = 21.4 Hz, ipso-Ph), 149.6 (s,
E
dx.doi.org/10.1021/ic301652u | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
ipso-Ph), 150.8 (d, 2JC,P = 10.5 Hz, ipso-Ph), 202.4 (dSat, 2JC,P = 7.9 Hz,
3.72−3.92 (1 H, m, OCH), 6.86−7.45 (15 H, m, 3Ph), 7.68 (1 H, d,
3JH,P = 329.3 Hz, PH). 13C{1H} NMR (C6D6): 22.4 (d, 3JC,P = 3.1 Hz,
CH3), 23.3 (d, 3JC,P = 5.0 Hz, CH3), 64.0 (d, 1JC,P = 20.4 Hz, PC), 75.5
(d, 2JC,P = 9.0 Hz, OCH), 127.6 (d, 5JC,P = 2.1 Hz, para-Ph), 128.5 (s,
meta-Ph), 131.0 (d, 3JC,P = 6.5 Hz, ortho-Ph), 142.9 (s, ipso-Ph), 196.8
2
1JC,W = 126.8 Hz, cis-CO), 207.0 (d, JC,P =14.8 Hz, trans-CO).
1
31P{1H} NMR (CDCl3, −40 °C): 253.5 (sSat, JP,W = 76.3 Hz) −
1
7
major, 252.4 (sSat, JP,W = 76.3 Hz) − minor. Li NMR (CDCl3, −40
°C): −0.31 (s).
2
1
2
(dSat, JC,P = 7.4 Hz, JC,W = 126.1 Hz, cis-CO), 198.8 (d, JC,P = 29.5
Hz, trans-CO). 31P{1H} NMR (C6D6): 115.21 (sSat, 1JP,W = 278.5 Hz).
IR (KBr; υmax/cm−1): 1922 (vs, CO), 1943 (vs, CO), 2073 (s, CO).
MS (EI, 70 eV): m/z (%): 658.1 (1.8) [(M)+]. Anal. Calcd. for
C27H23O6PW: C, 49.26; H, 3.52. Found: C, 49.23; H, 3.62.
X-ray Data Collection, Structure Solution, and Refinement.
Single crystals of complexes 2, 4, and 5 were obtained in diethyl ether
at −20 °C; crystals of 6 from THF/pentane mixture (slow diffusion)
at 25 °C. The data for crystals 2 and 5 were collected on a Bruker X8-
KappaApexII diffractometer at 123(2) K, and for 4 and 6 on a Nonius
KappaCCD device at 100(2) K by using graphite monochromated Mo
Kα radiation, λ = 0.71073 Å (Supporting Information, Table 1). The
structures were solved by Patterson methods (SHELXS-97) and
refined by full-matrix least-squares on F2 (SHELXL-97).
Crystallographic data of 2, 4−6 have been deposited at the
Cambridge Crystallographic Data Centre under the numbers CCDC
884453 (2), 884452 (4), 884454 (5), and 884455 (6). This data can
be obtained free of charge from the Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif. This material and
further informations are available free of charge in the Internet at
http://pubs.acs.org.
Isolation of [Li(12-crown-4)][(OC)5W{Ph3CPCl}] (3). To a
stirred solution of phosphane complex 2 (267.6 mg, 0.4 mmol) and
12-crown-4 (70 μL, 0.44 mmol) in 15 mL of diethyl ether was added
dropwise a solution of tBuLi in n-hexane (1.6 M, 0.28 mL) at −78 °C
to give a yellow solution with light-yellow precipitate. It was allowed to
warm up to −15 °C (ca. 2 h), and the liquid was removed via a
double-ended needle. The residue was washed with diethyl ether (3 ×
2 mL, −20 °C) and dried at 0 °C for 2 h at 10−2 mbar.
Yield: yellow solid, 253 mg (77%).31P MAS NMR: 255.9 ppm.
Synthesis of [(OC)5W{Ph3CP(Cl)C(O)Cl}] (4). To a stirred
solution of phosphane complex 2 (468 mg, 0.7 mmol) and 12-
crown-4 (0.122 mL, 0.77 mmol) in 10 mL of THF at −78 °C was
added dropwise a solution of tBuLi in n-hexane (1.6 M, 0.49 mL). The
obtained yellow solution (∼20 min) was cooled to −90 °C and quickly
transferred via a cooled double-ended needle to a precooled (−105
°C) intensively stirred solution of phosgene (ca. 20% in toluene, d
0.94, 2.21 mL). The mixture was warmed to −20 °C in a cooling bath,
and the volatiles were evaporated in vacuum. The residue was cooled
to −20 °C and extracted with cooled diethyl ether (40 mL). After
removing of the solvent in vacuum, the solid residue was washed with
diethyl ether (3 × 3 mL) to give 4 as a light-yellow powder.
1
Yield: 360 mg (74%); mp 174 °C (dec.). H NMR (C6D6): 6.91−
7.47 (m, 15 H, 3 Ph). 13C{1H} NMR (C6D6): 74.6 (d, 1JC,P = 3.6 Hz,
PCPh3), 128.6−128.9 (m, Ph), 129.6 (d, JC,P = 3.2 Hz, Ph), 130.8 (d,
JC,P = 6.9 Hz, Ph), 133.3 (d, JC,P = 7.9 Hz, Ph), 141.2 (s, ipso-Ph),
COMPUTATIONAL DETAILS
■
All calculations have been carried out with the ORCA electronic
structure program package35 with all structures being optimized in
redundant internal coordinates at the density functional theory (DFT)
level using the B3LYP36 functional together with the new efficient
RIJCOSX algorithm37 and the def2-TZVP basis set.38 For W the
[SD(60,MWB)] effective core potential was employed.39 A damped
semiempirical correction accounting for the major part of the
contribution of dispersion forces to the energy was included40 and
denoted with suffix -D after the name of the functional (B3LYP-D).
Solvent effects (THF) were taken into account via the COSMO
2
2
141.4 (d, JC,P = 6.1 Hz, ipso-Ph), 141.9 (d, JC,P = 5.7 Hz, ipso-Ph),
1
2
1
176.9 (d, JC,P = 13.6 Hz, PCO), 195.1 (dSat, JC,P = 5.9 Hz, JC,W
=
127.4 Hz, cis-CO), 197.1 (d, 2JC,P = 37.4 Hz, trans-CO). 31P{1H} NMR
(C6D6): 148.6 (sSat, 1JP,W = 278.5 Hz). IR (KBr; υmax/cm−1): 1747 (m,
CO), 1942 (vs, CO), 1959 (vs, CO), 2078 (s, CO). Anal. Calcd. for
C25H15Cl2O6PW: C, 43.07; H, 2.17. Found: C, 43.67; H, 2.58.
Synthesis of [(OC)5W{Ph3CPOC(H)Ph}] (5). To a freshly
synthesized Li/Clphosphinidenoid complex 3 (from phosphane
complex 2 (334 mg, 0.5 mmol), 12-crown-4 (87.5 μL, 0.55 mmol),
tBuLi (1.6 M in n-hexane, 0.35 mL) in 9 mL of THF) was added
benzaldehyde (0.1 mL, 1 mmol) at −78 °C leading to formation of a
white precipitate. The reaction mixture was warmed up to −15 °C in a
cooling bath (ca. 2 h), and volatiles were evaporated in vacuum. The
product was extracted with diethyl ether (40 mL), filtered through
Celite, and, after evaporation of the solvent in vacuum, washed with
diethyl ether (3 × 1 mL) at −50 °C, dried, and thus obtained as a
white solid.
solvation model.27 Atomic charges were computed from the Lowdin
̈
population analysis.41
ASSOCIATED CONTENT
■
S
* Supporting Information
Table of crystallographic parameters for 2, 4−6 and Cartesian
coordinates (Å) and energies (au) for all computed species.
Crystallographic data in CIF format. This material is available
free of charge via the Internet at http://pubs.acs.org.
Yield: 274.1 mg (78%); mp 128 °C. 1H NMR (C6D6): 4.14 (2 H, d,
2JH,P = 2.1 Hz, CHP), 6.97−7.24 (15 H, m, 3Ph), 7.64 (5 H, m, Ph).
13C{1H} NMR (C6D6): 60.4 (d, 1JC,P = 23.6 Hz, PCO), 67.7 (d, 1JC,P
=
8.1 Hz, PCPh3), 126.9 (d, JC,P = 3.9 Hz, Ph), 128.7 (d, JC,P = 2.1 Hz,
Ph), 129.0 (d, JC,P = 1.7 Hz, Ph), 129.1 (s, Ph), 131.1 (d, JC,P = 6.9 Hz,
Ph), 140.4 (d, 2JC,P = 2.3 Hz, ipso-Ph), 194.6 (dSat, 2JC,P = 8.2 Hz, 1JC,W
AUTHOR INFORMATION
■
Corresponding Author
*Fax: +49 228 739616. Tel: +49 228 735345. E-mail:
r.streubel@uni-bonn.de.
2
= 126.3 Hz, cis-CO), 196.3 (d, JC,P = 40.9 Hz, trans-CO). 31P{1H}
1
NMR (C6D6): 16.01 (sSat, JP,W = 311.5 Hz). IR (KBr; υmax/cm−1):
1905 (vs, CO), 1945 (vs, CO), 2077 (s, CO). MS (EI, 70 eV): m/z
(%): 704.1 (0.2) [M]+ .Anal. Calcd. for C31H21O6PW: C, 52.86; H,
3.01. Found: C, 52.89; H, 3.21.
Notes
The authors declare no competing financial interest.
Synthesis of [(OC)5W{Ph3CPOC(H)OiPr}] (5). To freshly
synthesized Li/Cl phosphinidenoid complex 3 (from phosphane
complex 2 (669 mg, 1 mmol), 12-crown-4 (0.17 mL, 1.1 mmol), tBuLi
(1.6 M in n-hexane, 0.7 mL) in 10 mL of THF) was added isopropyl
alcohol (1 mL, 13 mmol) at −78 °C. The reaction mixture was
warmed up to 0 °C in a cooling bath (ca. 2h). After further stirring at
25 °C for 1.5 h volatiles were evaporated in vacuum. The product was
purified by column chromatography (Al2O3, −15 °C, petrol ether/
dichloromethane = 10/2) to give 5 as a solid.
ACKNOWLEDGMENTS
■
We thank the Deutsche Forschungsgemeinschaft (STR 411/
26-1) and the COST action CM0802 “PhoSciNet” for financial
support; G.S. thanks Prof. A. C. Filippou for support.
DEDICATION
■
1
Dedicated to Professor Rheinhard Schmutzler on the occasion
of his 77th birthday.
Yield: 530 mg (80.5%); mp 107 °C (dec.). H NMR (C6D6): 0.69
3
3
(3 H, d, JH,H = 6.1 Hz, CH3), 0.80 (3 H, d, JH,H = 6.1 Hz, CH3),
F
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Article
̈
6894. (b) Nesterov, V.; Ozbolat-Schon, A.; Schnakenburg, G.; Shi, L.;
̈
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dx.doi.org/10.1021/ic301652u | Inorg. Chem. XXXX, XXX, XXX−XXX