32
G. Ludwig et al. / Inorganica Chimica Acta 429 (2015) 30–33
The
a
-sulfinyl-functionalized methyllithium compound 1 is one
The values gained by the 1H DOSY NMR experiment are listed in
Table S1.
of the few sulfur-functionalized methyllithium carbenoids of type I
and, to the best of our knowledge, the first one with a sulfinyl
group as nucleofugal leaving group. Lithium carbenoids of the type
–C(Li)Cl–S(O)Ar, which can be readily prepared from
aryl sulfoxides –CHCl–S(O)Ar or -chlorovinyl aryl sulfoxides
@CCl–S(O)Ar, were found to react as typical chloroalkyl lithium
carbenoids with -elimination of LiCl but not with a sulfinyl moi-
3.3. Decomposition of [Li2{CH2S(O)Ph}2(TMEDA)2] (1)
a-chloroalkyl
a
(A) An NMR tube filled with freshly prepared crystals of 1
(25 mg) and THF-d8 (0.75 mL) was sealed by melting and
exposed to daylight for 96 h. Finally, an 1H NMR spectrum
was recorded at 25 °C (Fig. S3). After addition of CD3OD
(0.1 mL) the solution was analyzed by GC–MS. Only diphenyl
disulfide was detected in the organic phase.
a
ety as leaving group [8].
3. Experimental
1H NMR (400 MHz, THF-d8): d 2.16 (s, 12H, 2 ꢂ N(CH3)2,
TMEDA), 2.32 (s, 4H, 2 ꢂ CH2, TMEDA), 5.37 (s, 4H,
2 ꢂ CH2, ethylene), 6.69–6.76 (m, 1H, p-H, SOPh), 7.05–7.15
(m, 4H, m-H + o-H, SOPh).
3.1. General comments
Organolithium compounds were prepared and handled under
purified argon using standard Schlenk techniques. Solvents
(diethyl ether, n-pentane, tetrahydrofuran, THF-d8, toluene-d8)
were dried over Na/benzophenone and freshly distilled prior to
use. NMR spectra (1H, 13C, 7Li) were recorded, if not otherwise stat-
ed, at 27 °C on a Varian VNMRS 400 spectrometer, operating at
400 MHz for 1H, 100 MHz for 13C and 156 MHz for 7Li. 1H and 13C
chemical shifts are relative to THF-d8 signals (dH = 1.72,
dC = 67.21) as internal references; 7Li NMR spectra were referenced
to a solution of LiCl in D2O (external; dLi = 0.00). The DOSY experi-
ment was performed under VNMRJ 3.0 and equipped with a 5 mm
PFG One NMR probe, z-gradient and temperature unit (27 °C). Dif-
fusion ordered NMR data were acquired by means of the Agilent
pulse program DgcsteSL_cc using a stimulated echo with self-com-
pensating gradient schemes and conventional compensation. The
length of the gradient pulse was set to 2.5 ms for 1H in combina-
tion with a diffusion period of 100 ms (THF-d8). Data were system-
atically accumulated by linearly varying the diffusion encoding
gradients over a range from 2% to 95% for 64 gradient increment
values. The signal decay dimension on the pseudo-2D data was
generated by Fourier transformation of the time-domain data.
DOSY plots were generated by use of the DOSY processing module
of VNMRJ. GC–MS analyses were performed on a HP 5890 Series II/
HP 5972 (Hewlett Packard) using a capillary column (30 m HP
5MS). Products were identified by reference substances and by
mass spectrometry. [Li2{CH2S(O)Ph}2(TMEDA)2] (1) was prepared
according to the previously reported method [22].
(B) In a closed Schlenk tube equipped with a condenser, a solu-
tion of freshly prepared crystals of 1 (150 mg) in toluene
(25 mL) was heated to reflux for 4 h, during which time
the initial pale yellow solution became brown in color. Sub-
sequently the gaseous phase was analyzed by means of GC–
MS showing exclusively the formation of ethylene. Then, an
aqueous solution of NH4Cl (25 mL; 30%) was added. After
phase separation and extraction of the aqueous phase with
diethyl ether (3 ꢂ 10 mL), the combined organic phases
were analyzed by GC–MS showing the formation of diphenyl
disulfide (66%), ethylbenzene (4%), m/o/p-xylene (3%), iso-
propylbenzene (23%) and n-propylbenzene (4%) (newly
formed products were summed up to 100%).
Appendix A. Supplementary material
Supplementary data associated with this article can be found, in
References
[2] K.H. Dötz (Ed.), Top. Organomet. Chem. 13 (2004) 1.
1 in THF-d8. 1H NMR (400 MHz): d 1.96 (s, br, 2H, CH2Li), 2.16 (s,
12H, 2 ꢂ N(CH3)2, TMEDA), 2.31 (s, 4H, 2 ꢂ CH2, TMEDA), 7.18–
7.22 (m, 1H, p-H, SOPh), 7.28–7.32 (m, 2H, m-H, SOPh), 7.92–7.94
(m, 2H, o-H, SOPh). 13C NMR (100 MHz): d 34.7 (s, LiCH2), 46.2 (s,
N(CH3)2, TMEDA), 58.8 (s, CH2N, TMEDA), 127.8 (s, p-C, SOPh),
127.9 (s, o-C, SOPh), 128.0 (s, m-C, SOPh), 155.0 (s, i-C, SOPh). 7Li
NMR (156 MHz): d 0.1 (s, Li).
1 in toluene-d8. 1H NMR (400 MHz): d 2.04 (s, br, 2H, CH2Li),
2.10 (s, 12H, 2 ꢂ N(CH3)2, TMEDA), 2.15 (s, 4H, 2 ꢂ CH2, TMEDA),
6.81–6.84 (m, 1H, p-H, SOPh), 7.24–7.30 (m, 2H, m-H, SOPh),
7.37–7.39 (m, 2H, o-H, SOPh). 13C NMR (100 MHz): d 31.7 (s,
LiCH2), 45.5 (s, N(CH3)2, TMEDA), 57.4 (s, CH2N, TMEDA), 117.5
(s, p-C, SOPh), 119.8 (s, o-C, SOPh), 123.3 (s, m-C, SOPh), 129.9 (s,
i-C, SOPh). 7Li NMR (156 MHz): d 5.6 (s, Li).
3.2. DOSY experiment of [Li2{CH2S(O)Ph}2(TMEDA)2] (1)
The 1H DOSY NMR experiment was carried out with freshly pre-
pared crystals of 1 (25 mg), that were transferred to an NMR tube.
After adding the internal standards (1-phenylnaphthalene, PhN;
tetramethylsilane, TMS; diethyl ether; 10 lL each) and THF-d8
(0.75 mL) the 1H DOSY NMR spectrum was run at 27 °C (cf.
Fig. S1). The correlation between logD and logMr (D = diffusion
coefficients; Mr = relative molecular mass) is presented in Fig. S2.