On the structure and ambiphilicity of a sulfonyl substituted α-chloro lithium base

Article abstract of DOI:10.1039/c3dt52800f

An α-chloro lithium base stabilised by a sulfonyl and thiophosphinoyl moiety was selectively prepared by lithiation of its protonated precursor and oxidation of the corresponding dilithio methandiide. The carbenoid-like compound was found to be remarkably stable even at room temperature and thus allowed for its spectroscopic characterisation in solution and in the solid state. Its ambiphilic nature was tested and compared with typical carbenoids both experimentally and by computational methods. The electronic stabilisation results in its thermal stability but considerably reduces the ambiphilic character limiting the reactivity patterns generally observed for lithium carbenoids.

Full text of DOI:10.1039/c3dt52800f

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On the structure and ambiphilicity of a sulfonyl
substituted α-chloro lithium base†
Cite this: Dalton Trans., 2014, 43,
4320
Julia Becker and Viktoria H. Gessner*
An α-chloro lithium base stabilised by a sulfonyl and thiophosphinoyl moiety was selectively prepared by
lithiation of its protonated precursor and oxidation of the corresponding dilithio methandiide. The carbe-
noid-like compound was found to be remarkably stable even at room temperature and thus allowed for
its spectroscopic characterisation in solution and in the solid state. Its ambiphilic nature was tested and
compared with typical carbenoids both experimentally and by computational methods. The electronic
stabilisation results in its thermal stability but considerably reduces the ambiphilic character limiting the
reactivity patterns generally observed for lithium carbenoids.
Received 7th October 2013,
Accepted 15th October 2013
DOI: 10.1039/c3dt52800f
www.rsc.org/dalton
Introduction
Main group metal carbenoids are usually defined as com-
pounds with a metallated carbon atom which additionally
carries a potential leaving group. Most commonly lithium,
magnesium and zinc are used as metals, while halides and
ethers are reported to be best suited as nucleofugal substitu-
ents.1 This constitution results in the unique ambiphilic char-
acter of carbenoids which is particularly manifested in the
widely applied cyclopropanation or homologation reactions.2
Usually, lithium chloride carbenoids are amongst the most
reactive carbenoids, often being only isolable at temperatures
even below −78 °C. As such, the first isolation of a Li/Cl carbe-
noid I was only accomplished in 1993 by Boche and co-
workers.3 It took another 14 years to prepare the first room
temperature stable carbenoid II, in which the lithium is
efficiently coordinated by the two thiophosphinoyl moieties.4
Despite the lack of a C–Li contact in II the carbenoid character
was manifested by the preparation of a Pd carbene complex
or – most recently – by B–H bond activation via LiCl
elimination (Fig. 1).
Fig. 1 Structure of the first isolated Li/Cl carbenoid I (C1–Cl 1.855(7);
C1–Li 2.145(14) Å) and the first room temperature stable carbenoid II
(1.781(2) Å).
shifted by up to 280 ppm compared to the protonated ana-
logues.6 For example lithiation of tribromomethane (δC
=
9.7 ppm) results in a shift of Δδ = 142.5 ppm in the corres-
ponding Li/Br carbenoid (δC = 152.2 ppm) or lithiation of
chloromethane in a shift by Δδ = 32.3 ppm.1 This observation
can be explained by the polarisation of the C–X bond upon
metallation and an increased carbene-like character. Likewise,
XRD analyses revealed a distinct elongation of the C–X bond in
the solid state structures of carbenoids. As such, Boche and
co-workers reported on an elongated C–Cl bond in Cl3CLi by
12.6 ppm.7 In contrast, only a small C–N bond lengthening is
typically observed in α-lithiated amines (except for aziridines8),
which led to the conclusion that they usually behave as
normal carbanions rather than as carbenoids.9
Nevertheless, it is well known that the reactivity of carbe-
noids – as is also the case for other organometallic reagents –
is influenced by several factors beyond the nature of the metal
atom and of the leaving group. We have become particularly
interested in the impact of electronic stabilisation effects of
α-substituents on the stability and carbenoid character.10 We
particularly focussed on the question of how stabilisation
affects or limits the ambiphilic nature. So far only two room
temperature stable carbenoids (II and its iodine analogue)
The ambiphilic nature of carbenoids has been proven not
only by their reactivity,5 but also by means of NMR spec-
troscopy and X-ray diffraction (XRD) analysis. As such, the car-
benoid carbon atom is usually found to be strongly deshielded
in the 13C NMR spectrum featuring resonances down-field
Institut für Anorganische Chemie, Julius-Maximilians-Universität Würzburg,
Am Hubland, 97074 Würzburg, Germany. E-mail: vgessner@uni-wuerzburg.de;
Tel: (+49)931-31-84163
†Electronic supplementary information (ESI) available: Experimental, spectro-
scopic, computational details and crystallographic data of the presented com-
pounds. CCDC 959178, 959179 and 963531. For ESI and crystallographic data in
CIF or other electronic format see DOI: 10.1039/c3dt52800f
4320 | Dalton Trans., 2014, 43, 4320–4325
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have been reported, but the carbenoid character has only been
Treatment of precursor 2 with methyllithium afforded car-
manifested in the case of II. Here, we report on the synthesis benoid 3 in quantitative yield as evidenced by monitoring the
and the molecular and electronic structure of a room tempera- reaction process by 31P NMR spectroscopy. Isolation gave 3 as
ture stable α-chloro lithium base, which is stabilised by both a a colourless solid in 67% yield. Alternatively, 3 was found to be
sulfonyl and a thiophosphinoyl moiety. We show that the sta- accessible by oxidation of dilithio methandiide 5, which can
bilising effects considerably reduce the ambiphilic character be prepared by double deprotonation of 1 with methyl-
preventing reactivity patterns typically observed for lithium lithium.11 Treatment of 5 with hexachloroethane enabled the
carbenoids. However, a weakened carbenoid nature is pre- isolation of carbenoid 3 in even 82% yield. Compound 3 is
served as evidenced by the formation of a carbene complex.
characterised by a single, slightly high-field shifted resonance
in the 31P NMR spectrum at δP = 40.3 ppm (cf. 2: δP
=
45.5 ppm) and one signal at δLi = 1.02 ppm in the 7Li NMR
spectrum. The carbenoid carbon atom was found to resonate
at δC = 56.0 ppm (1JPC = 91.5 Hz), which is high-field shifted
Results and discussion
2
compared to the protonated precursor 2 (δC = 72.2 ppm, JPC
=
The desired compound 3 was targeted via two different syn-
thetic strategies: (i) via metallation of the protonated precursor
2 and (ii) via oxidation of the dilithio methandiide 5, a
method which has only previously been reported by P. Le
Floch and co-workers.4 First, the chlorinated compound 2 was
synthesised from the protonated precursor 1 by lithiation and
treatment with hexachloroethane in moderate isolated yields
of 42% (Scheme 1). 2 was characterised by multi-nuclear NMR
spectroscopy, elemental analysis and single crystal X-ray dif-
fraction analysis. 2 crystallises in the monoclinic space group
33.8 Hz) and down-field shifted relative to the monolithiated
2
analogue 4 (δC = 44.0 ppm, JPH = 109.8 Hz).11 The increased
shielding of the metallated carbon atom compared to 2
accounts for non-polarisation of the C–Cl bond and thus for
only a weak (or even no) carbenoid character. The increased
1JPC coupling constant in 3 suggests a higher s-character in the
respective bond. It is noteworthy that the NMR spectra (includ-
ing the 7Li NMR spectrum) of 3 are well resolved indicating no
fluxional behaviour in solution. Carbenoid 3 is a rare example
of a room temperature stable α-chloro lithium base.4,12 No
decomposition was observed in the solid even after storage for
weeks under an inert atmosphere.
P2 /c. The asymmetric unit contains two molecules differing in
1
the configuration of the central carbon atom (only one of
which is depicted in Fig. 2).
In order to gain insight into the bonding situation of carbe-
noid 3 single crystals were grown by diffusion of pentane into
a THF solution of 3. Carbenoid 3 crystallises as a dimer in the
ˉ
triclinic space group P1 (Fig. 3). The central structural motif
consists of an (S–O–Li–O)2 eight-membered ring through
which the two carbenoid molecules are connected. The
lithium atoms are solely coordinated by the oxygen atoms of
Scheme 1 Synthesis of carbenoid 3.
Fig. 3 Molecular structure of carbenoid 3. Ellipsoids drawn at the 50%
probability level. Hydrogen atoms are omitted for clarity. Selected bond
lengths [Å] and angles [°]: Cl1–C1 1.757(2), Cl2–C20 1.758(2), S1–P1 1.967(1),
S2–O2 1.455(2), S2–O1 1.458(2), S2–C1 1.665(2), S3–P2 1.970(1), S4–O4
1.455(2), S4–O3 1.455(2), S4–C20 1.670(2), P1–C1 1.760(2), P2–C20
1.753(2), O1–Li2 1.949(4), O2–Li1 1.913(4), O3–Li1 1.927(4), O4–Li2
1.924(4); S2–C1–P1 122.7(1), S2–C1–Cl1 111.4(1), P1–C1–Cl1 119.1(1), S4–
C20–Cl2 111.1(1), S4–C20–P2 122.84(1), Cl2–C20–P2 120.3(1).
Fig. 2 Molecular structure of 2. For crystallographic details see the
ESI.†
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the sulfonyl moiety and two THF molecules. No lithium the P–C and S–C bonds in this series of compounds due to
carbon bond is formed, which is typical of such sulfonyl sub- electrostatic interactions with the positively charged phos-
stituted carbanions.13 The metallated carbon atoms are phorus and sulphur atoms. The charge at the carbenoid
slightly pyramidalised (sum of angles of 353.2(1) and carbon atom still amounts to qC = −1.00. In all metallated
354.2(1)°) leading to stereogenic carbon centers. Both carbe- compounds the Wiberg bond indices (WBI) of the X–Li bonds
noid subunits of the dimer differ in the configuration at that are close to zero thus accounting for their essentially electro-
carbon atom. The C–P (av. 1.757(2) Å) and C–S (av. 1.668(2) Å) static nature. The WBI of the C–Cl bond in carbenoid 3 was
bond lengths are considerably shortened in comparison to the found to be 0.996. This value is only slightly smaller than the
protonated precursor 2, but are lengthened compared to the one found for the protonated precursor 2 (WBI = 1.024) and
monolithiated and dilithiated congeners 4 and 5 (Table 1). still corroborates with a strongly bound chloride substituent
This bond shortening in the metallated compounds is the and thus a weak carbenoid character. Furthermore, the nega-
result of considerable electrostatic interactions within the tive charge of the chloro substituent increases only slightly,
P–C–S backbone.14 The less pronounced shortening in 3 com- thus indicating a weak leaving group character. The same ten-
pared with 4 and 5 accounts for less electrostatic attraction dencies are observed for monomeric aggregates of carbenoid 3
due to the electron withdrawing chloride substituent. However, with different coordination modes including Li–C interactions,
no bond lengthening of the C–Cl bond (2: 1.763(3) Å, 3: 1.758(2) suggesting that aggregation has only a little influence on the
Å) is observed, which is usually the case for other carbenoids electronic structure of 3 (see Fig. 4).
(see above). The broad P–C–S angle of 122.8(1)° (average value)
For comparison purposes we also looked at the properties
indicates a change in hybridisation from sp3 to sp2 which is of H2CClLi (dimeric and monomeric solvates, Fig. 3) as a
1
well in line with the increased JPC coupling constant (see typical lithium chloride carbenoid and II as an electronically
above). A comparison of the most important bond lengths and stabilised carbenoid. For H2CClLi, the expected changes and
angles of 3 and its congeners 2, 4 and 5 is given in Table 1.
carbenoid characteristics are observed upon metallation of
Overall, the experimental observations (NMR spectroscopy CH3Cl: (i) an increase of the negative charge of the chloro sub-
and XRD analysis) indicate only a weakly pronounced carbe- stituent, (ii) lengthening of the C–Cl bond (>0.1 Å) and (iii) a
noid character of 3. To further understand the electronic struc- decrease of the WBI(C–Cl). A different picture, however, is
ture of
3 we performed DFT studies using the B3LYP again obtained for the bis(phosphonium) substituted system
functional in combination with the 6-311+g(d,p) basis set. II. Here, the same features are observed as those found for
Therefore, model systems were chosen in which the phenyl compound 3 (see ESI†). As the carbenoid character of II has
substituents are replaced by methyl groups and the coordinat- been proven experimentally, these findings suggest that the
ing THF by dimethyl ether (see ESI† for computational details carbenoid character cannot strictly be connected with a C–X
and comparison with other functionals and basis sets). The bond lengthening or an increase of the charge of the leaving
structural parameters of the central structural motif of 3 and group.
of the optimised model system are in good agreement with
Overall, the computations show that the efficient stabili-
each other (e.g. calcd C–S 1.703 Å). The natural bond orbital sation of the negative charge in 3 by the sulfonyl and thiophos-
(NBO) analysis (Table 1) shows a clear increase of the charge at phinoyl moiety (electrostatic interaction and negative
the metallated carbon atom from 2 to 5. This is well in line hyperconjugation effects) results in its increased stability and
with the experimentally observed bond length shortening of weakens the ambiphilic nature. In order to experimentally
explore the carbenoid character we studied the nucleophilicity
and electrophilicity of 3 by means of typical reactions known
Table 1 Comparison of the structural parameters (average values for 2,
3, 4 and 5), NMR data [C6D6 (2, 3), THF-d8 (4, 5)] and calculated
properties
2
3
4
5
C–S [Å]
C–P [Å]
C–Cl [Å],
exp (calcd)a
P–C–S [°]
δC, 1JPC
1.814(3)
1.868(3)
1.668(2)
1.757(2)
1.651(2)
1.740(3)
1.613(3)
1.710(3)
—
1.763(3) (1.792) 1.758(2) (1.800) —
115.2(2)
72.2, 33.8
122.8(1)
56.0, 91.5
124.6(2)
44.0, 109.8 50.6 (br)
121.4(2)
[ppm, Hz]
qC (calcd)a −0.774
−1.001
0.644
−0.033
0.996
−1.208
0.645
—
—
0.011
−1.447
0.562
—
qLi (calcd)a
—
qCl (calcd)a −0.019
WBI C–Cla 1.024
—
WBI C–Lia
—
0.015
0.176, 0.017
(average)
a Values correspond to methyl substituted model systems. For
computational details, see the ESI.
Fig. 4 Calculated model systems of 3 (top) and H2C(Cl)Li (bottom) and
calculated natural charges [B3LYP/6-311+g(d,p)].
4322 | Dalton Trans., 2014, 43, 4320–4325
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Scheme 2 Reactivity of compound 3.
for carbenoids (Scheme 2). In terms of nucleophilicity, 3 was
found to react with electrophiles, such as Ph2PCl and MeI, in
the expected salt elimination reactions – comparable to
“simple” organolithium reagents – giving the corresponding
compounds 6a and 6b (see ESI†). In contrast, no cyclopropana-
tion reaction with cyclohexene – typical of less stabilised carbe-
noids – was observed. Also, no substitution of the chloro
substituent by methyllithium (in toluene or THF) was found,
but instead Cl/Li exchange was found. This was evidenced by
monitoring the reaction via 1H NMR and 31P NMR spec-
troscopy showing broadened signals for the dilithium species
5. Aqueous work-up delivered sulfone 1 in excellent yields.
3 was also tested as a source for the formation of novel
carbene complexes as this has been successfully accomplished
for the stable carbenoid II. However, the reaction with metal
precursors mainly leads to the formation of complex product
mixtures. The best results were obtained with [Pd(PPh3)4], indi-
cating the formation of carbene complex 7 analogous to II
(Scheme 3). 7 is characterised by two doublets in the 31P NMR
spectrum resonating at δP = 17.9 and 39.9 ppm (3JPP = 38.7 Hz).
However, the complex turned out to be labile and repeatedly
decomposed in the course of the work-up procedure. This
instability of complex 7 can probably be attributed to the weak
coordination ability of the sulfonyl moiety.15 Two further pro-
ducts could be identified, one being the thioketone complex 9
(δP = −1.29, 24.2, and 28.5 ppm) and the other one being the
protonated dimeric complex 8 (δP = 52.4 ppm), which is
formed by protonation of 7 followed by dimerisation. Selective
thioketone formation was recently observed with a more reac-
tive Li/Cl carbenoid.10a Complex 8 could be isolated as a yellow
solid in 10% yield and crystallised by slow diffusion of diethyl
ether into a solution of 8 in dichloromethane (Fig. 5). Alterna-
tively, 8 can be selectively prepared from the deprotonated pre-
cursor 4 and [(PPh3)2PdCl2] in 75% yield. The complex forms a
C2 symmetric dimer, in which the palladium centre features a
slightly distorted square-planar geometry by coordination of
the thiophosphinoyl unit and the carbon atom. No coordi-
nation of the sulfonyl moiety is observed. The carbon atom
in 8 becomes stereogenic. However, only the (R,R)- and
(S,S)-couples are observed in the crystal.
Fig. 5 Molecular structure of complex 8. Ellipsoids drawn at the 50%
probability level. Phenyl hydrogen atoms are omitted for clarity. Selected
bond lengths [Å] and angles [°]: Pd–C1 2.093(3), Pd–S1 2.3866(8), S1–P
2.0080(10), S2–O1 1.440(2), S2–O2 1.442(2), S2–C1 1.753(3), P–C1
1.780(3); C1–Pd–C1’ 94.33(16), C1–Pd–S1 81.96(8), C1’–Pd1–S1
174.33(8), S1–Pd–S1’ 102.05(4).
Overall the experimental findings confirm that compound 3
possesses only a weakened ambiphilic character compared
with non-stabilised Li/Cl carbenoids and in many cases reacts
as a “simple” α-chloro organolithium base. However, as indi-
cated by the reactivity towards the palladium(0) precursor
some carbenoid character is left allowing for the typical LiCl
elimination. We would like to point out that replacing the sul-
fonyl moiety with a silyl group fully recovers the high reactivity
and ambiphilicity of the carbenoid.10
Conclusions
In conclusion, we reported on the preparation of a room-temp-
erature stable α-chloro organolithium compound via a depro-
tonation and oxidation protocol. The electronic stabilisation
by a sulfonyl and thiophosphinoyl moiety results in its remark-
able stability but considerably decreases the electrophilic
nature and thus the carbenoid character. These studies show
that despite the fact that Li/Cl carbenoids are usually regarded
as one of the most reactive carbenoid species their stability
and reactivity are crucially influenced by α-substituents. By a
careful choice of the substitution pattern control of the reacti-
vity should thus be possible.
Experimental
General
All experiments were carried out under a dry, oxygen-free
argon atmosphere using standard Schlenk techniques.
Involved solvents were dried over sodium or potassium (or over
P4O10, CH2Cl2) and distilled prior to use. H2O is distilled
water. Organolithium reagents were titrated against diphenyl-
acetic acid prior to use. 1H, 7Li, 13C, and 31P NMR spectra were
recorded on Avance-500, Avance-400 or Avance-300 spec-
trometers at 22 °C if not stated otherwise. All values of the
Scheme 3 Reaction of carbenoid 3 with [Pd(PPh3)4].
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2
chemical shift are in ppm regarding the δ-scale. All spin–spin 4JPC = 2.96 Hz, CHPPh,para), 130.4 (CHSPh,para), 132.8 (d, JCP
=
1
coupling constants (J) are presented in hertz (Hz). To display 10.7 Hz, CHPPh,ortho), 136.5 (d, JPC = 92.9 Hz, CPPh,ipso), 135.3
multiplicities and signal forms correctly the following (CHSPh,para), 145.4 (CSPh,ipso). 13P{1H}NMR (202.5 MHz, C6D6):
abbreviations were used: s = singlet, d = doublet, t = triplet, δ = 40.3. 7Li NMR (194.4 MHz, C6D6): δ = 1.02. Calc for
m = multiplet, br = broad signal. Signal assignment was sup- C54H62Cl2Li2O8P2S4: C, 58.20, H, 5.61, S 11.51. Found: C,
ported by DEPT and HMQC experiments. Elemental analyses 58.31, H, 5.38, S 11.64.
were performed using an Elementar vario MICRO-cube
(b) From dianion 5. A solution of 52.8 mg (0.22 mmol)
elemental analyzer. All reagents were purchased from Sigma- hexachloroethane in 2 mL THF was slowly added to a suspen-
Aldrich, ABCR, Rockwood Lithium or Acros Organics and used sion of 100 mg (0.20 mmol) dianion 5 in 4 mL tetrahydrofur-
without further purification. Compounds 1, 4 and 5 were pre- ane at −30 °C. After stirring for 4 h at low temperature, the
pared according to literature procedures.11
suspension turned into a colourless solution and 31P{1H} NMR
spectroscopy showed complete conversion. The solvent was
evaporated in vacuo, and the residue was taken up in 6 mL dry
Preparation of 2
A solution of 864 mg (2.32 mmol) sulfone 1 in 30 mL dry tetra- toluene and filtered to remove the formed LiCl. Diffusion of
hydrofurane was cooled to −78 °C, 2.40 mL (2.88 mmol) nBuLi pentane into the saturated toluene solution gave carbenoid 3
(1.20 M in hexane) were added and the resulting suspension as colourless crystals (91.0 mg, 81.7 µmol, 82%).
was allowed to warm to room temperature. After stirring for
For NMR spectra and synthetic procedures of all other com-
4 h the reaction mixture was added dropwise to a solution of pounds, see the ESI.†
0.66 g (2.79 mmol) hexachloroethane in 7 mL dry diethyl ether
at −78 °C. Stirring for 15 h at ambient temperature gave an
orange solution, which was treated with 20 mL water. The
Computational details
aqueous layer was separated, extracted with diethyl ether (3 × All calculations were performed without symmetry restrictions.
15 mL) and the organic layer was dried with Na2SO4. After the Starting coordinates were obtained directly from the crystal
evaporation of the solvents, purification of the crude product structure analysis. All calculations were done with the Gaus-
by chromatography on silica gel (diethyl ether–pentane, 3/1 v/v, sian 09 (Revision B.01) program package.16 Geometry optimis-
Rf = 0.50) gave the desired product as a colourless crystalline ations were performed using Density-Functional Theory (DFT)
solid (400 mg, 0.98 mmol, 42%). 1H NMR (300.1 MHz, with the B3LYP (Becke 3-parameter-Lee-Yang-Parr) functional17
2
CD2Cl2): δ = 5.69 (d, JPH = 5.11 Hz, 1H, PCHS), 7.50–7.62 (m, and the 6-311+G(d,p) basis set. Harmonic vibrational fre-
8H, CHPPh,meta/para + CHSPh,meta), 7.67–7.73 (m, 1H, CHSPh,para), quency analyses were performed on the same levels of theory.
7.86–7.90 (m, 2H, CHSPh,ortho), 7.94–8.07 (m, 4H, CHPPh,ortho). The vibrational frequency analyses showed no imaginary fre-
1
13C{1H} NMR (125.8 MHz, C6D6): δ = 72.2 (d, JPC = 33.8 Hz, quencies. Natural bond orbital analyses were performed using
4
PCS), 128.3 (CHSPh,para), 128.5 (d, JPC = 0.82 Hz, CHPPh,para), the NBO 3.1 program implemented in the Gaussian program
4
1
128.6 (d, JPC = 0.72 Hz, CHPPh,para), 130.4 (d, JPC = 48.2 Hz, package. For further details, calculated energies and Cartesian
1
CPPh,ipso), 131.06 (d, JPC
(CHSPh,meta), 132.1 (d, JPC = 3.11 Hz, CHPPh,meta), 132.2 (d,
= 3.14 Hz, CHPPh,meta), 132.5 (d, JPC = 10.5 Hz,
CHPPh,ortho), 133.0 (d, JPC = 10.6 Hz, CHPPh,ortho), 134.4
=
47.7 Hz, CPPh,ipso), 131.12 coordinates of the energy-optimised structures, see the ESI.†
3
2
3JPC
2
X-ray crystallography
(CHSPh,ortho), 137.5 (CSPh,ipso). 31P{H} NMR (121.5 MHz, Crystallographic data for compound 2: C19H16ClO2PS2, M =
CD2Cl2): δ = 45.5. Calc. for C19H16ClO2PS2: C, 56.09, H, 3.96, 406.86 g mol−1, monoclinic, P21/c, a = 14.6305(10) Å, b =
S 15.76. Found: C, 56.38, H, 4.06, S 15.96.
24.0872(16) Å, c = 10.8747(8) Å, β = 98.829(2)°, V = 3786.9(5) Å3,
T = 100(2) K, Z = 8, 45 022 reflections measured, 6660 indepen-
dent reflections (Rint = 0.0406). R1 = 0.0461 [reflections with
Preparation of carbenoid 3
(a) Via deprotonation of 2. 0.12 mL (0.11 mmol) of I > 2σ(I)], wR2 = 0.1277 (all data).
methyllithium (0.98 M in diethyl ether) was added to a solu- Crystallographic data for compound 3: C54H62Cl2O8P2S4Li2,
tion of 39.6 mg (97.3 µmol) of compound 2 in 1 mL tetrahydro- M = 1114.00 g mol−1, triclinic, P1, a = 10.7500(9) Å, b =
18.4650(15) Å, 84.134(2)°,
ˉ
furane at −78 °C. The solution was allowed to warm to room 14.3394(11) Å,
c
=
α
=
β =
temperature. Reaction monitoring by 31P{1H} NMR spec- 14.3394(11)°, γ = 84.850(2)°, V = 2733.8(4) Å3, T = 100(2) K, Z =
troscopy showed complete conversion after 4 h. Colourless 2, 50 285 reflections measured, 11 260 independent reflections
crystals of 3 were obtained directly from the cooled reaction (Rint = 0.0348). R1 = 0.0438 [reflections with I > 2σ(I)], wR2 =
mixture (36.1 mg, 32.4 µmol, 67%). 1H NMR (500.1 MHz, 0.1257 (all data).
C6D6): δ = 1.34–1.39 (m, 8H, CH2-THF), 3.63–3.68 (m, 8H, CH2–
Crystallographic data for compound 8: C38H32O4P2PdS4,
THF), 6.96–7.04 (m, 9H, CHmeta,para), 8.03–8.08 (m, 4H, M = 849.22 g mol−1, monoclinic, C2/c a = 23.4275(16) Å, b =
CHPPh,ortho), 8.11–8.13 (dd, 2H, 3JHH = 1.74 Hz, CHSPh,ortho). 13
C
9.8149(7) Å, c = 17.4155(12) Å, β = 116.776(2)°, V = 3575.1(4) Å3,
{1H} NMR (125.8 MHz, C6D6): δ = 25.7 (CH2-THF), 56.0 (d, T = 100(2) K, Z = 4, 21 522 reflections measured, 3145 indepen-
1JPC = 91.5 Hz, PCS), 68.1 (CH2-THF), 126.8 (CHSPh,ortho), 127.8 dent reflections (Rint = 0.0357). R1 = 0.0278 [reflections with
3
(d, JPC = 12.7 Hz, CHPPh,meta), 128.4 (CHSPh,meta), 130.3 (d, I > 2σ(I)], wR2 = 0.0715 (all data).
4324 | Dalton Trans., 2014, 43, 4320–4325
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Crystal data for 2,
CCDC-959178 (2), CCDC-959179 (3) and CCDC-963531 (8)
contain the supplementary crystallographic data for this paper.
3
and
8
are given in the ESI.†
7 A. Müller, M. Marsch, K. Harms, J. C. W. Lohrenz and
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9 For α-lithiated amines, see: (a) D. Seebach, J. Hansen,
P. Seiler and J. M. Gromek, J. Organomet. Chem., 1985, 285,
1; (b) W. Bauer, G. Müller, R. Pi and P. v. R. Schleyer,
Angew. Chem., Int. Ed. Engl., 1986, 25, 1103;
(c) C. Strohmann and V. H. Gessner, Angew. Chem., Int. Ed.,
2007, 46, 8281; (d) V. H. Gessner and C. Strohmann, J. Am.
Chem. Soc., 2008, 130, 14412.
Acknowledgements
This work was supported by the DFG, the FCI and the
Alexander von Humboldt Foundation. We also thank
Rockwood Lithium GmbH for the supply of chemicals.
Notes and references
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