A surprisingly stable 1-(chlorosilyl)-2-phosphaethenyllithium compound, RCl2SiC(Li)=PMes

Article abstract of DOI:10.1002/ejic.200400595

RCl₂Si-C(Li)=PMes* (1) (R = 9-methylfluoren-9-yl, Mes* = 2,4,6-tri-tert-butylphenyl), considered as a key intermediate in the synthesis of the heteroallene RClSi=C=PMes*, was obtained from RCl₂Si-C(Cl)=PMes* by lithium/chlorine exchange with nBuLi and evidence for its identity was obtained by hydrolysis. Remarkably, however, it failed to undergo a lithium salt elimination to form the corresponding chlorophosphasilaallene, RClSi=C=PMes*, even under prolonged heating in toluene, As shown by theoretical studies (RHF/ 3-21G* and RHF/6-31G* //RHF/3-21G* level), interactions between the lithium ion and the π-systems of the substituents at the phosphorus and silicon atoms could partly account for this stability. The lithium compound 1 reacts with methanol or chlorotrimethylsilane leading to new silylphosphaalkenes. The reaction of the lithium derivative 1 with benzaldehyde gave a four-membered heterocycle with an exocyclic P=C bond which virtually corresponds to the product of a [2+2] cycloaddition between the Si=C and C=O double bonds. Wiley-VCH Verlag GmbH & Co. KGaA, Germany, 2005.

Full text of DOI:10.1002/ejic.200400595

FULL PAPER
A Surprisingly Stable 1-(Chlorosilyl)-2-phosphaethenyllithium Compound,
RCl2SiC(Li)=PMes*
Gabriela Cretiu Nemes,[a,b] Henri Ranaivonjatovo,[b] Jean Escudié,*[b]
Ioan Silaghi-Dumitrescu,[a] Luminita Silaghi-Dumitrescu,[a] and Heinz Gornitzka[b]
Keywords: Phosphaalkenes / (Chlorosilyl)phosphaethenyllithium / Chlorophosphasilaallene / Molecular modelling /
Cation-π interaction
RCl2Si–C(Li)=PMes* (1) (R = 9-methylfluoren-9-yl, Mes* =
2,4,6-tri-tert-butylphenyl), considered as a key intermediate
in the synthesis of the heteroallene RClSi=C=PMes*, was ob-
tained from RCl2Si–C(Cl)=PMes* by lithium/chlorine ex-
change with nBuLi and evidence for its identity was obtained
by hydrolysis. Remarkably, however, it failed to undergo a
lithium salt elimination to form the corresponding chloropho-
sphasilaallene, RClSi=C=PMes*, even under prolonged
heating in toluene. As shown by theoretical studies (RHF/
3-21G* and RHF/6-31G**//RHF/3-21G* level), interactions
between the lithium ion and the π-systems of the substituents
at the phosphorus and silicon atoms could partly account for
this stability. The lithium compound 1 reacts with methanol
or chlorotrimethylsilane leading to new silylphosphaalkenes.
The reaction of the lithium derivative 1 with benzaldehyde
gave a four-membered heterocycle with an exocyclic P=C
bond which virtually corresponds to the product of a [2+2]
cycloaddition between the Si=C and C=O double bonds.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2005)
steric shielding of the bulky groups in PhTipSi=C=PMes*
(Tip = 2,4,6-triisopropylphenyl) is not sufficient to prevent
the target molecule from coupling with itself and, conse-
quently, the study of its chemical behaviour was limited.
Due to the presence of three reaction sites (the Si=C and
P=C double bonds as well as the phosphorus lone pair),
such compounds should be extremely interesting from a
synthetic point of view. Various cycloadducts could be ob-
tained with unsaturated species, making these allenic deriv-
atives powerful building blocks in heterocyclic and or-
ganometallic chemistry. In order to increase the synthetic
utility of such compounds, we have tried to attach a chlo-
rine atom to the silicon atom which could allow function-
alisation of SiCP systems. Thus, it seemed interesting to
prepare a phosphasilaallene, the main objective being to ob-
tain a stable derivative to facilitate the study of its reactivity.
Herein we describe the synthesisof the stable chloro-li-
thio compound RCl2Si–C(Li)=PMes* (R = 9-methylflu-
oren-9-yl) 1 from dichlorophosphasilapropene 2, along with
its characterisation showing that it exhibits a chemical be-
haviour which could be theoretically expected from the tar-
get phosphasilaallene RClSi=C=PMes* 3.
Introduction
Silenes, the silicon counterparts of olefins, have chal-
lenged chemists for many years. Although the initial claim
for producing an Si=C linkage dates back to 1912,[1] isola-
tion of a stable silene was first achieved in 1981.[2] This
major breakthrough, combined with the syntheses of the
stable disilene Mes2Si=SiMes2 (Mes
= 2,4,6-trimeth-
ylphenyl)[3] and diphosphene Mes*P=PMes* (Mes* =
2,4,6-tri-tert-butylphenyl)[4] paved the way for the remark-
able and thriving chemistry of heavier multiple-bonded
main group elements from which other bonding patterns
such as heterocumulative double-bond systems have
emerged.[5] A stable 1-silaallene ϾSi=C=CϽ, in which the
carbon atom involved in the double bond to the silicon
atom adopts sp-hybridisation, was reported a decade
later.[6] We have been interested in 1,3-phosphasilaallenes,
i.e. compounds with phosphorus and silicon atoms (thus,
two heavier group 14 and 15 elements) at the terminal posi-
tions of the heteroallene skeleton and reported the hitherto
unique ϾSi=C=P– derivative some years ago.[7] The latter
readily undergoes dimerisation above –30 °C. Clearly, the
[a] Universitatea Babes-Bolyai Cluj, Facultatea de Chimie si Ingi-
nerie Chimica,
Results and Discussion
Kogalniceanu Nr. 1, 400084 Cluj-Napoca, Romania
Fax: +40-264-190818
Vicinal
dihalophosphametallapropenes
ϾM(X)–
E-mail: isi@chem.ubbcluj.ro
C(Cl)=P– (X = F, Cl; M = Si,[7] Ge[8]) are suitable precur-
sors to the corresponding heteroallenes. Lithiation of the
central carbon atom occurs smoothly at low temperature
through a lithium/halogen exchange and the subsequent
[b] Hétérochimie Fondamentale et Appliquée, UMR 5069, Uni-
versité Paul Sabatier,
118 Route de Narbonne, 31062, Toulouse cedex 04, France
Fax: +33-561558204
E-mail: escudie@chimie.ups-tlse.fr
Eur. J. Inorg. Chem. 2005, 1109–1113
DOI: 10.1002/ejic.200400595
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1109

J. Escudié et al.
FULL PAPER
lithium salt elimination gives rise to a metal–carbon double
bond adjacent to the existing P=C bond which remains in-
tact throughout the whole procedure. The final step in the
synthesis of stable 1-silaallenes also involves lithium salt eli-
mination from the closely related 3-fluoro-2-lithio-3-sila-
propenes ϾSi(F)–C(Li)=CϽ.[5e,6,9]
The above-described synthetic approach was applied for
the target chlorophosphasilaallene. Substitution with the 9-
methylfluorenyl group at the silicon atom was intended to
provide extra steric protection for the desired double bond.
The coupling of the carbenoid Cl(Li)C=PMes*[10] with
trichloro(9-methylfluoren-9-yl)silane[11] afforded the antici-
pated trichlorophosphasilapropene 2 in good yield. A 31P
NMR analysis of the reaction mixture suggested that only
one isomer of compound 2 was formed (δP = 328.1 ppm).
Because of the severe steric hindrance of the Mes* group,
the more accessible trans-chlorine atom in Cl2C=PMes*
can be expected to undergo an easier lithium/halogen ex-
change with nBuLi. This favours the formation of the (E)-
carbenoid Cl(Li)C=PMes* which hence led to the (Z)-pho-
sphasilapropene 2 when mixed with the starting trichlorosil-
ane. The (Z) configuration of derivative 2 was confirmed
by an X-ray diffraction study (Figure 1). The P=C distance
[1.669(3) Å] matches the average value reported for such
bonds (1.67 Å).[5c]
Scheme 1.
constant (67.9 Hz). A similar value (66.4 Hz) was reported
by Bickelhaupt et al. for the (E) isomer of Mes*P=C(H)
[10a]
SiMe3
whereas the coupling constant for the (Z) isomer
is smaller (54.4 Hz).
According to Wiberg, the 1,2-elimination of LiX to form
an Si=C double bond involves dipolar intermediates B
(Scheme 2).[12]
Scheme 2.
In our case, the non-elimination of LiCl means that the
position of the equilibrium is shifted to form A, probably
because of the presence of two chlorine atoms on the silicon
atom. The natural charges on the carbon atom in the model
carbanions [Cl3–xHxSi–C=PH]– at the RHF/6-31+G** level
(Table 1) show that by increasing the number of chlorine
atoms on the silicon atom, the negative charge on the car-
bon atom increases. This in turn favours the A form in
Scheme 2.
Figure 1. Molecular structure of 2 (thermal ellipsoids at the 50%
probability level; H atoms are omitted for clarity); selected bond
lengths [Å] and angles [°]: C(1)–P(1) 1.669(3), C(1)–Cl(1) 1.747(2),
C(1)–Si(1) 1.850(3), P(1)–C(2) 1.833(3), Si(1)–C(20) 1.883(3), Si(1)–
Cl(2) 2.0404(9), Si(1)–Cl(3) 2.0524(10); P(1)–C(1)–Cl(1) 125.92(15),
P(1)–C(1)–Si(1) 119.65(14), C(1)–P(1)–C(2) 104.42(11), C(1)–Si(1)–
C(20) 115.89(11), C(20)–Si(1)–Cl(2) 109.47(8), C(20)–Si(1)–Cl(3)
109.97(8)
Table 1.Natural charges on the carbon atom in the [Cl3–xHxSi–
C=PH]– anions
Model
Natural charge on the
carbon atom
[H3Si–C=PH]–
[ClH2Si–C=PH]–
[Cl2HSi–C=PH]–
[Cl3Si–C=PH]–
–1.224
–1.315
–1.362
–1.393
Treatment of 2 with tert-butyllithium resulted in the ex-
pected metallation and caused the 31P NMR signal to shift
downfield (δP = 441.4 ppm). Further evidence for the ensu-
In order to obtain a deeper understanding of the ob-
ing lithium derivative RCl2SiC(Li)=PMes* 1 was obtained served reluctance of 1 to lose LiCl, molecular orbital calcu-
by formation of its hydrolysis product (Scheme 1). lations on various conformers of the model
Compound 1 is stable under a rigorously maintained in- CpЈCl2SiC(Li)=PMes* system (CpЈ = 1-methylcyclopen-
ert gas at room temperature and fails to eliminate lithium tadienyl) were carried out at the RHF/3-21G* level of
chloride to give 3 even under prolonged heating at reflux in theory, with full optimisation of the geometry. Note that
toluene. However, attempts to isolate the highly air- and this model retains the main steric and electronic features of
moisture-sensitive 1 by crystallisation at –30 °C led to the 1 (through the Mes* group on P and the CpЈ group on Si).
hydrolysis product 4 due to adventitious water. The (E) iso- The influence of the solvent on the relative stability of these
mer was exclusively obtained, as expected from the configu- conformers has been inferred from single point calculations
1
ration of starting 1 and was proved by the JP=C coupling with the PCM solvation model of Tomasi by using two sol-
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A Surprisingly Stable 1-(Chlorosilyl)-2-phosphaethenyllithium Compound
FULL PAPER
Table 2. Relative energies [kJ mol–1] and natural charges on Li in 1a and 1b
Conformer
Gas phase
DMSO
Relative energy
Toluene
Relative energy
Natural charge
Natural charge
Relative energy
Natural charge
1a
1b
30.00
0.0
0.897
0.885
47.00
0.0
0.900
0.887
40.42
0.0
0.898
0.886
vents (DMSO and toluene). The two lowest energy con- able from the chlorophosphasilaallene 3 with these reac-
formers (1a and 1b) are shown in Figure 2. Table 2 includes tants (Scheme 3).
the relative energies of these conformers calculated in the
gas phase and in the two solvents as well as the natural
charges on Li.
Figure 2. Lowest energy conformers of CpЈCl2SiC(Li)=PMes* (hy-
drogen atoms omitted); note the special position of Li in 1b al-
lowing for strong cation–π interactions
Scheme 3.
The lowest energy conformer 1b exhibits strong electro-
static interactions between Li and both π systems (Mes*
Interestingly, compound 1 readily reacts with benzalde-
and CpЈ) as shown by the following distances: Li–ipso-
hyde to afford oxasiletane 7 with an exocyclic P=C double
C(Mes*) 2.357 Å, Li–centroid(Mes*) 2.380 Å, Li–ipso-
bond in the form of one isomer as shown by 31P NMR
C(CpЈ) 2.325 Å, Li–centroid(CpЈ) 2.247 Å. These distances
spectroscopy (δP = 339.4 ppm) (Scheme 3). From the 2JP,CO
are in good agreement with those determined from X-ray
coupling constant (10.2 Hz) it seems that 7 exists as the (E)
analyses of similar interactions.[13]
isomer (Mes* and Si trans to each other). This stereochem-
The chlorine atoms in 1b are located in unfavourable po-
istry is in agreement with the postulated configuration of
sitions for intramolecular elimination of LiCl. Intermo-
1 and the mechanism of the reaction. Similar values were
lecular condensation is also quite improbable due to the
[16]
2
obtained by Appel and Bickelhaupt
for JP,C in
very efficient steric protection of the Li cation (see the CPK
representation of 1b in Figure 2). Note also that because of
these cation···π interactions, the natural charge on Li does
not change on going from gas phase to DMSO or toluene
solution. Conformer 1a is higher in energy both in the gas
phase and in solution and, presumably, this arrangement is
more difficult to achieve in the real system 1. This order is
also maintained at the RHF/6-31G**//RHF/3-21G* level
where 1a is still higher by 15.22 kJ mol–1. Thus, cation···π
interactions between Li and the Mes* and fluorenyl groups
in 1 could account for its failure to eliminate lithium chlo-
ride. Such interactions have been recently highlighted by an
X-ray diffraction analysis of a lithium (difluorosilyl)phos-
phide –Si(F2)–P(Li)– which failed to undergo lithium fluo-
ride elimination up to 100 °C.[14]
Mes*P=C–C systems [(E) isomer 10–15 Hz, (Z) isomer 20–
60 Hz]. In the closely related germanium compound 8c, the
structure of which was established by an X-ray determi-
2
nation, a JP,CO coupling constant of 38.7 Hz was observed
for the (Z) isomer (Scheme 4). In the absence of an X-ray
structural study, the stereochemistry of the four-membered
ring (Ph and Cl in cis or trans positions) could not be deter-
mined.
Lithium···π
interactions
in
the
case
of
Scheme 4.
RCl2SiC(Li)=PMes* 1 also favour a shift in the position of
the equilibrium to form A in accordance with the calcula-
Though the latter reaction likely proceeds through an ad-
tions and this could also explain the lack of elimination of dition/elimination pathway, the four-membered ring 7 vir-
LiCl. A similar reluctance to form an Si=C double bond by tually conforms to the cycloaddition product of the Si=C
salt elimination has been previously reported.[15]
double bond of the corresponding chlorophosphasilaallene
The lithio compound 1 reacts with excess methanol or with the starting aldehyde without participation of the con-
chlorotrimethylsilane to give the silylphosphaalkenes 5 and tiguous P=C double bond as was found earlier for the Ge
6, respectively. The same derivatives should also be obtain- congener tBuTipGe=C=PMes*.[8]
Eur. J. Inorg. Chem. 2005, 1109–1113
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1111

J. Escudié et al.
FULL PAPER
74.6 Hz, P=C or i-C of Mes*), 149.1 and 151.6 (o- and p-C of
Mes*) ppm. 31P NMR (Et2O, [D8]toluene): δ = 441.4 ppm.
Similarly, a silenoid, ϾSi(Cl)–C(Li)Ͻ, has already been
observed to behave as a synthetic equivalent of the corre-
sponding silene in its reaction with carbonyl com-
pounds.[15e] The study of the chemical behaviour of 1
towards various unsaturated species is now under investiga-
tion.
Formation of RCl2Si–C(H)=PMes* (4): A white waxy solid of 4
(95% purity) was obtained due to hydrolysis when a solution of the
lithium compound 1 in Et2O, prepared as described previously
from 2 (1.00 g, 1.66 mmol), was kept at –30 °C for a week. Yield
1
0.85 g (90%). H NMR (CDCl3): δ = 1.25 (s, 18 H, o-CMe3), 1.32
2
(s, 9 H, p-CMe3), 1.85 (s, 3 H, Me), 6.75 (d, JP,H = 22.5 Hz, 1 H,
CH), 7.28–7.91 (m, 10 H, arom. H of R and m-CH of Mes*) ppm.
13C NMR (CDCl3): δ = 19.1 (br. s, Me), 31.6 and 34.3 (br., CMe3),
35.0 and 35.2 (o- and p-CMe3), 38.1 (C-9), 120.2 and 122.0 (C-4,
-5 and m-CH of Mes*), 124.9 and 127.2 (C-1–3, C-6–8), 141.0,
146.0, 150.2 and 152.6 (o- and p-C of Mes*, C-10–13), 156.6 (d,
Experimental Section
General Remarks: All manipulations were carried out under N2 or
Ar using standard Schlenk techniques with solvents freshly distilled
from sodium/benzophenone. 1H, 13C and 31P NMR spectra were
recorded in CDCl3 with a Bruker AC 200 instrument at 200.1, 50.1
and 81.01 MHz, respectively, except for compound 1 which was
measured in [D8]toluene with a Bruker AC 400 spectrometer at
100.6 MHz. Mass spectra were recorded with a Hewlett–Packard
5989 A spectrometer by EI at 70 eV. Melting points were deter-
mined using a Leitz microscope heating stage 250. Elemental analy-
ses were performed by the “Service de Microanalyse de l’Ecole de
Chimie de Toulouse”. The carbon atoms of the fluorenyl group are
numbered as shown in Scheme 5.
1JP,C = 67.9 Hz,P=C) ppm. 31P NMR (CDCl3): δ = 375.3 (2JP,H
=
22.5 Hz) ppm.
Synthesis of R(OMe)2Si–C(H)=PMes* (5): RCl2Si–C(Li)=PMes*
(1.66 mmol) prepared as previously described was treated with ex-
cess methanol (1 mL). The reaction mixture was filtered and the
solution concentrated in vacuo followed by addition of pentane.
Cooling to –20 °C gave 5 as a white solid (90% purity). Yield 0.87 g
(88%). 1H NMR (CDCl3): δ = 1.28 (s, 18 H, o-CMe3), 1.34 (s, 9
2
H, p-CMe3), 1.66 (s, 3 H, Me), 3.27 (s, 6 H, OMe), 6.98 (d, JP,H
= 22.0 Hz, 1 H, CH), 7.20–7.80 (m, 10 H, arom. H of R and m-
CH of Mes*) ppm. 13C NMR (CDCl3): δ = 19.1 (Me), 31.5 and
33.8 (br., CMe3), 35.1, 38.1 and 38.9 (o- and p-CMe3, C-9), 45.5
(br., OMe), 119.9 (br., C-4, -5 and m-CH of Mes*), 124.8 and 126.5
(C-1–3, C-6–8), 140.4, 145.8, 152.2 and 153.1 (o- and p-C of Mes*,
2
C-10–13) ppm. 31P NMR (CDCl3): δ = 362.2 (d, JP,H = 22.0 Hz)
ppm. MS (EI): m/z (%) = 558 (5) [M]+, 527 (1) [M – OMe]+, 379
(40) [M – R]+, 323 (33) [M – R – tBu + 1]+, 179 (100) [R]+.
Scheme 5.
Synthesis of RCl2Si–C(SiMe3)=PMes* (6): RCl2Si–C(Li)=PMes*
(1.66 mmol) in Et2O (10 mL) was treated with excess chlorotri-
methylsilane (0.5 mL) at room temperature. The lithium salt was
removed by filtration and the solution concentrated in vacuo fol-
lowed by addition of pentane. Cooling to –20 °C afforded 6 as a
Synthesis of RCl2Si–C(Cl)=PMes* (2): A sample of Cl2C=PMes*
(1.14 g, 3.18 mmol) was dissolved in THF (15 mL) and cooled to
–80 °C. Under nitrogen, tBuLi (2 mL of a 1.7 m hexane solution, 1
equiv.) was added to form ClLiC=PMes*. This solution was slowly
added to a solution of trichloro(9-methylfluoren-9-yl)silane (1.00 g,
3.18 mmol) in THF (10 mL) at –80 °C. The mixture was slowly
warmed to room temperature with magnetic stirring over 2 h. After
filtration, the solution was concentrated in vacuo and pentane
(10 mL) was added. Cooling to –20 °C led to 2 as a crystalline
1
white solid. Yield 0.90 g(85%). M.p. 116 °C. H NMR (CDCl3): δ
= –0.33(s, 9 H, SiMe3), 1.12 (s, 18 H, o-CMe3), 1.28 (s, 9 H, p-
CMe3), 1.92 (s, 3 H, Me), 7.23–7.91 (m, 10 H, arom. H of R and
m-CH of Mes*) ppm. 13C NMR (CDCl3): δ = 0.4 (SiMe3), 19.6
(Me), 29.9 and 31.6 (br., CMe3), 37.1 and 37.6 (o- and p-CMe3),
45.3 (C-9), 118.3 and 119.6 (C-4, -5 and m-CH of Mes*), 125.1 and
127.2 (C-1–3, C-6–8), 141.0, 146.0, 150.1 and 153.2 (o- and p-C of
Mes*, C-10–13), 177.2 (d, 1JP,C = 90.5 Hz, P=CSi) ppm. 31P NMR
(CDCl3): δ = 433.7 ppm. MS (EI): m/z (%) = 638 (15) [M]+, 623
(15) [M – Me]+, 566 (20) [M – SiMe3 + 1]+, 459 (20) [M – R]+, 403
(15) [M – R – tBu + 1]+, 275 (22) [ArP – 1]+, 179 (65) [R]+, 57
(100) [tBu]+. C36H49Cl2PSi2 (638.83): calcd. C 67.58, H 7.72; found
C 67.81, H 7.88.
1
product. Yield 1.49 g (78%). M.p. 131 °C. H NMR (CDCl3): δ =
1.12 (s, 18 H, o-CMe3), 1.23 (s, 9 H, p-CMe3), 1.88 (s, 3 H, Me),
7.28–7.85 (m, 10 H, arom. H of R and m-CH of Mes*) ppm. 13C
NMR (CDCl3): δ = 21.4 (br., Me), 30.3 (br., CMe3), 35.0 (p-CMe3),
37.8 (o-CMe3), 46.2 (C-9), 120.3 and 122.0 (C-4, -5 and m-CH of
Mes*), 125.2 and 127.2 (C-1–3, C-6–8), 134.0 (d, JP,C = 63.0 Hz, i-
C of Mes*), 141.1 and 146.1 (C-10–13), 151.0 and 153.1 (o- and p-
C of Mes*), 155.7 (d, JP,C = 83.5 Hz, P=CCl) ppm. 31P NMR
(CDCl3): δ = 328.1 ppm. MS (EI): m/z (%) = 602 (5) [M]+, 587 (10)
[M – Me]+, 565 (5) [M – Cl]+, 423 (30) [M – R]+, 179 (95) [R]+, 57
(100) [tBu]+. C33H40Cl3PSi (602.09): calcd. C 65.83, H 6.70; found
C 66.10, H 6.91.
Synthesis of Oxasiletane 7: A solution of RCl2Si–C(Li)=PMes*,
prepared from 2 (1.00 g, 1.66 mmol) in diethylether (20 mL), was
cooled to –60 °C under nitrogen. To the stirred solution was slowly
added benzaldehyde (0.19 g, 1.75 mmol). The solution was warmed
to room temperature with magnetic stirring over 2 h. The reaction
mixture was then filtered to remove LiCl and the solution concen-
trated in vacuo. Addition of pentane and cooling to –20 °C gave a
waxy yellow solid which could not be obtained completely pure
(90% purity) but was unambiguously identified as 7 by NMR spec-
troscopy and mass spectrometry. Yield 0.85 g (77%). 1H NMR
(CDCl3): δ = 1.35 (br., 27 H, CMe3), 1.80 (s, 3 H, Me), 5.80 (d,
3JP,H = 13.6 Hz, 1 H, OCH), 6.75–8.10 (m, 15 H, Ph, arom. H of
Synthesis of RCl2Si–C(Li)=PMes* (1): A solution of RCl2Si–
C(Cl)=PMes* (1.30 g, 2.16 mmol) in diethyl ether (20 mL) was co-
oled to –80 °C under nitrogen. To the stirred solution was slowly
added tBuLi (1.27 mL of a 1.7 m hexane solution, 1 equiv.) and
the solution was then warmed to room temperature with magnetic
stirring over 2 h. 13C and 31P NMR spectroscopic analyses of the
brown solution showed nearly quantitative formation of 1. 13C
NMR (400 MHz, [D8]toluene): δ = 18.6 (Me), 31.2 and 33.9
(CMe3), 33.3 (CMe3), 38.4 (C-9), 120.0 (C-4, -5), 124.7, 126.7 and R and m-CH of Mes*) ppm. 13C NMR (CDCl3): δ = 13.8 (Me),
127.1 (C-1–3, C-6–8), 141.0 and 145.7 (C-10–13), 144.4 (d, JP,C 31.4 and 33.6 (br., CMe3), 37.1 and 38.3 (o- and p-CMe3) 47.7 (C-
=
1112
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A Surprisingly Stable 1-(Chlorosilyl)-2-phosphaethenyllithium Compound
FULL PAPER
2
[7]
L. Rigon, H. Ranaivonjatovo, J. Escudié, A. Dubourg, J.-P.
Declercq, Chem. Eur. J. 1999, 5, 774–781.
Y. El Harouch, H. Gornitzka, H. Ranaivonjatovo, J. Escudié,
9), 113.1 (d, JP,CO
= 10.2 Hz, OCH), 120.2–130.0 (C-1–8
and m-CH of Mes*), 140.8–154.0 (o- and p-C Mes*, C-10–13) ppm.
31P NMR (CDCl3): δ = 339.4 (d, JP,H = 13.6 Hz) ppm. MS (EI):
3
[8]
[9]
J. Organomet. Chem. 2002, 643–644, 202–208.
m/z (%) = 636 (2) [M]+, 545 (3) [M – PhCH – 1]+, 456 (5)
[M – R – 1]+, 394 (3) [M – ClSiR]+, 379 (3) [ArP=CCHPh]+, 350
(8) [ArP=C–SiCl + 1]+, 179 (35) [R]+, 105 (30) [PhCO]+, 57 (100)
[tBu]+.
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Computational Details: A complete search of the conformational
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Crystal Data for 2: C33H40Cl3PSi, M = 602.06, monoclinic, C2/c,
a = 16.661(2) Å, b = 10.730(1) Å, c = 36.380(3) Å, β = 90.284(2)°,
V = 6504.0(11) Å3, Z = 8, T = 193(2) K. 18162 reflections (6577
independent, Rint = 0.0340) were collected at low temperature using
an oil-coated shock-cooled crystal with a Bruker-AXS CCD 1000
diffractometer with Mo-Kα radiation (λ = 0.71073 Å). The struc-
ture was solved by direct methods (SHELXS-97)[21] and all non-
hydrogen atoms were refined anisotropically using the least-squares
method on F2.[22] Largest electron density residue: 0.403 e·Å–3, R1[I
Ͼ 2σ(I)] = 0.0511 and wR2 (all data) = 0.1187 with R1 = Σ||Fo| –
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|Fc||/Σ|Fo| and wR2 = [Σw(Fo – Fc ) /Σw(Fo2)2]0.5. CCDC-233371
contains the supplementary crystallographic data for this paper.
These data can be obtained free of charge at www.ccdc.cam.ac.uk/
conts/retrieving.html [or from the Cambridge Crystallographic
Data Centre, 12, Union Road, Cambridge CB2 1EZ, UK; Fax:
+44-1223-336-033; E-mail: deposit@ccdc.cam.ac.uk].
2
2 2
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Acknowledgments
G. C. N. thanks the NATO for support through the postdoctoral
grant no. 376651J.
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Received July 9, 2004
Eur. J. Inorg. Chem. 2005, 1109–1113
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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