Inorganic Chemistry
Article
desilylation of the respective bis(trimethylsilyl)chalcogenides
cooling the combined mother liquor and washings to −20 °C.
[
BMPyr][TMS-Se] was isolated as a colorless solid. Yield: 1.10 g (3.74
TMS E (E = S, Se, Te) with known methylcarbonate ILs. Our
2
mmol, 81%). Mp: 127.8−128.4 °C (5 K/min, dec, MeCN/Et O).
synthesis is based on the observed desilylating capability of the
highly nucleophilic methylcarbonate anion, followed by
irreversible decarboxylation. This method offers a high yield
and, in terms of cation and anion variability, broad access to
well-soluble and pure silylchalcogenolates with purely organic
cations. Upon exploration of the scope of this method,
desilylation could be extended to representative C- and N-
silyl derivatives, allowing a safe access to organic azide and
cyanide salts, difficult to obtain in pure form by other methods.
The new ionic chalcogenides were investigated regarding their
decomposition temperatures and spectroscopic properties
2
Elem anal. Calcd for C H N Se Si : C, 49.0; H, 9.9; N, 4.8. Found:
1
2
29
1
1
1
−1
C, 48.5; H, 9.8; N, 5.3. IR (νmax/cm ): 2941 (m), 2889 (w), 1465
(
(
w), 1383 (w), 1231 (m), 1004 (w), 931 (w), 818 (vs), 735 (m), 667
1
m), 621 (m). H NMR (300.1 MHz, DMSO-d ): δ 0.09 (s, 9H, TMS-
6
3
Se), 0.93 (t, JHH = 7.5 Hz, 3H, CH CH ), 1.25−1.38 (m, 2H,
2
3
CH CH ), 1.62−1.73 (m, 4H), 2.08 (br s, 4H), 2.99 (s, 3H, NMe),
2
3
13
3.29−3.35 (m, 2H), 3.39−3.54 (m, 4H). C NMR (75.5 MHz,
DMSO-d ): δ 9.2 (3C, TMS-Se), 13.4 (1C), 19.2 (1C), 21.0 (1C),
6
2
9
24.9 (1C), 47.5 (br s, 2C), 62.8 (br s, 2C), 63.3 (br s, 1C). Si NMR
77
(
59.7 MHz, DMSO-d ): δ −4.7 (s). Se NMR (57.3 MHz, DMSO-
6
d ): δ −417.5 (s).
6
Synthe sis of N-Butyl-N-methylpyrrolidinium
(
NMR and IR). The crystal structures of 6 and 5 constitute
the first structurally characterized examples of uncoordinated
trimethylsilyl)chalcogenolate anions. These are highly valuable
(
Trimethylsilyl)tellurolate ([BMPyr][TMS-Te], 3). N-Butyl-N-
methylpyrrolidinium methylcarbonate (1.00 g, 4.60 mmol, 1.00
equiv) was dissolved in acetonitrile (8 mL), and the solution was
(
precursors for the synthesis of polychalcogenides with purely
organic cations, as demonstrated by the selective synthesis of
pyrrolidinium hexasulfides via a redox reaction with elemental
sulfur. The XRD structural characterization of the side products
cooled to 0 °C and degassed three times. TMS Te (1.28 g, 4.66 mmol,
2
1.01 equiv) was added dropwise, whereupon the solution turned
slightly red. The mixture was stirred for 30 min at 0 °C and a further
60 min at ambient temperature. All volatile components were removed
in vacuo, and a reddish-gray solid remained, which proved to be pure
according to elemental analysis. [BMPyr][TMS-Te] was isolated in a
yield of 1.44 g (4.19 mmol, 91%). Mp: 120.4−121.2 °C (5 K/min, dec,
MeCN). Elem anal. Calcd for C H N Si Te : C, 42.0; H, 8.5; N, 4.1.
[
BMPyr] Se3 and [DMPyr] Te demonstrates that this
2 4 12
strategy can be extended to the higher homologues. We are
confident that the now readily available title compounds
Cat[TMS-E] (E = S, Se, Te) will expand the starting material
basis for many chemists working in the topical areas of metal
chalcogenido clusters, (silyl)chalcogenidometallates, metal
chalcogenide semiconductor materials, and polychalcogenide
redox mediators.
1
2
29
1
1
1
−1
Found: C, 42.4; H, 8.7; N, 4.5. IR (νmax/cm ): 2939 (m), 2880 (w),
1
6
0
461 (w), 1230 (m), 1060 (w), 933 (w), 822 (vs), 738 (m), 672 (m),
1
16 (s). H NMR (300.1 MHz, DMSO-d ): δ 0.32 (s, 9H, TMS-Te),
6
3
.92 (t, J = 7.4 Hz, 3H, CH CH ), 1.25−1.38 (m, 2H, CH CH ),
HH
2
3
2
3
1.61−1.75 (m, 4H), 2.08 (br s, 4H), 3.01 (s, 3H, NMe), 3.32−3.41 (m,
13
2
H), 3.44−3.56 (m, 4H). C NMR (75.5 MHz, DMSO-d ): δ 10.1
6
EXPERIMENTAL SECTION
Details of solvothermal syntheses and isolation of methylcarbonate
salts and other starting materials, e.g., TMS Te, as well as synthetic
(3C, TMS-Te), 13.4 (1C), 19.2 (1C), 21.0 (1C), 24.9 (1C), 47.5 (br s,
■
29
2
C), 62.7 (br s, 2C), 63.3 (br s, 1C). Si NMR (79.5 MHz, DMSO-
125
d ): δ −27.0 (s). Te NMR (126.2 MHz, DMSO-d ): δ −1142.0 (s).
6
6
2
Synthesis of Bis(N,N-dimethylpyrrolidinium)hexasulfide
([DMPyr] S , 11). A suspension of sulfur (201 mg, 6.27 mmol, 4.95
2 6
equiv) in THF (20 mL) was added to [DMPyr][TMS-S] (520 mg,
.53 mmol, 2.00 equiv). The mixture immediately turned bright red
Synthesis of N-Butyl-N-m ethylpyrrolid inium
Trimethylsilyl)thiolate ([BMPyr][TMS-S], 1). N-Butyl-N-methyl-
2
(
and was stirred for 3 days, after which a fine red precipitate had
formed. The solid was filtered, washed with THF (10 mL), and dried
in fine vacuum. 11 was isolated in a yield of 485 mg (1.23 mmol, 98%).
Mp: 128.2−128.8 °C (5 K/min, dec, THF). Elem anal. Calcd for
pyrrolidinium methylcarbonate (617 mg, 2.84 mmol, 1.00 equiv) was
dissolved in acetonitrile (5 mL), and the solution was cooled to 0 °C.
TMS S (688 mg, 3.86 mmol, 1.36 equiv) was added dropwise, and the
2
mixture was stirred for 1 h at 0 °C and a further 30 min at ambient
temperature. The solution was concentrated in fine vacuum to two-
thirds of its original volume, and diethyl ether (2 mL) was added.
Storage at −25 °C yielded colorless crystals. The precipitate was
filtered over a precooled frit, washed with diethyl ether (10 mL), and
dried in fine vacuum. [BMPyr][TMS-S] was isolated as a colorless
solid. Yield: 514 mg (2.08 mmol, 73%). Mp: 120.9−121.9 °C (5 K/
min, dec, MeCN/Et O). Elem anal. Calcd for C H N S Si : C, 58.2;
3
4
C H N S : C, 36.7; H, 7.2; N, 7.1; S, 50.0. Found: C, 36.9; H, 7.3;
12 28
2 6
−1
N, 8.4; S, 52.51. IR (νmax/cm ): 2982 (w), 1459 (w), 1000 (w), 975
(w), 935 (w), 818 (w), 503 (vs), 439 (w). H NMR (300.1 MHz,
1
DMSO-d
4H, NCH
52.3 (br s, 2C, NMe
Synthesis of Hexamethylguanidinium Azide ([Me
2). Hexamethylguanidinium methylcarbonate (288 mg, 1.31 mmol,
.00 equiv) was dissolved in acetonitrile (8 mL) and the mixture
): δ 2.12 (br s, 4H, CH
), 3.14 (s, 6H, NMe
). C NMR (75.5 MHz, DMSO-d ): δ 22.1 (2C, CH
), 65.8 (br s, 2C, NCH ).
), 3.51 (br s,
6
2
2
13
),
2
2
6
2
2
Gua]N ,
2
12 29
1
1
1
6
3
1
H, 11.8; N, 5.7; S, 12.95. Found: C, 58.3; H, 12.2; N, 5.8; S, 12.5. IR
−
1
1
(
1
νmax/cm ): 2938 (m), 1478 (w), 1384 (w), 1231 (m), 1030 (w),
1
cooled to 0 °C. (Trimethylsilyl)azide (189 mg, 1.64 mmol, 1.25 equiv)
was added dropwise, whereupon gas evolution could be witnessed.
The mixture was stirred at 0 °C for 20 min and at ambient
temperature for 30 min. Trace amounts of solid residue were removed
by syringe filtration, and all volatile components were removed in fine
vacuum. The solid residue was recrystallized from a mixture of
007 (w), 937 (w), 814 (vs), 735 (m), 663 (m), 633 (s), 499 (s). H
3
NMR (300.1 MHz, DMSO-d ): δ −0.07 (s, 9H, TMS-S), 0.93 (t, J
6
HH
=
7.5 Hz, 3H, CH CH ), 1.25−1.38 (m, 2H, CH CH ), 1.62−1.73 (m,
2
3
2
3
4
3
1
2
H), 2.08 (br s, 4H), 3.01 (s, 3H, NMe), 3.33−3.39 (m, 2H), 3.44−
.56 (m, 4H). 13C NMR (75.5 MHz, DMSO-d ): δ 8.9 (3C, TMS-S),
6
3.4 (1C), 19.2 (1C), 21.0 (1C), 24.9 (1C), 47.4 (br s, 2C), 62.7 (br s,
C), 63.3 (br s, 1C). 29Si NMR (99.4 MHz, DMSO-d ): δ −0.7 (s).
acetonitrile and diethyl ether at −25 °C. [Me Gua][N ] was isolated
6
6 3
Synthesis of N-Butyl-N-m ethylpyrrolid inium
in a yield of 152 mg (0.816 mmol, 62%) as colorless crystals. Mp:
(
Trimethylsilyl)selenolate ([BMPyr][TMS-Se], 2). N-Butyl-N-
299.9−300.7 °C (5 K/min, dec, MeCN/Et O). Elem anal. Calcd for
2
methylpyrrolidinium methylcarbonate (997 mg, 4.59 mmol, 1.00
equiv) was dissolved in acetonitrile (10 mL), and the solution was
C H N : C, 45.1; H, 9.7; N, 45.1. Found: C, 45.1; H, 9.5; N, 45.5. IR
7
18
6
−1
(νmax/cm ): 3288 (w), 3000 (w), 2898 (w), 2803 (w), 1994 (vs),
cooled to 0 °C and degassed three times. TMS Se (1.24 g, 5.50 mmol,
1596 (vs), 1477 (m), 1402 (vs), 1254 (m), 1147 (m), 1069 (m), 895
2
1
1
0
.20 equiv) was added dropwise, and the mixture was stirred for 1 h at
(m), 630 (w), 536 (w). H NMR (300.1 MHz, DMSO-d ): δ 2.87 (s,
6
18H, Me). 13C NMR (75.5 MHz, DMSO-d ): δ 39.4 (6C, Me), 162.3
°C and a further 30 min at ambient temperature. The solution was
6
concentrated in fine vacuum to half of the original volume and stored
at −20 °C. The resulting suspension was filtered over a precooled frit,
and the precipitate was washed with diethyl ether (10 mL) and dried
in fine vacuum. A second crop of material was obtained analogously by
(1C, Cquart).
Synthesis of Hexamethylguanidinium Cyanide ([Me Gua]-
[CN], 13). Hexamethylguanidinium methylcarbonate (210 mg, 0.958
mmol, 1.00 equiv) was dissolved in acetonitrile (8 mL) and the
6
9
573
Inorg. Chem. 2015, 54, 9568−9575