Organometallics
Article
1
3
(
CH ), 47.7 (CH ). C NMR (150.9 MHz, [D ]THF): δ 8.5 (CH −
Synthesis of [{(tmeda)Li} Mg(C H ) ] (5). Solid (thf) MgCl
2
2
2
8
2
2
4
8 2
1.5
1
1
Mg, J(C,H) = 104.1 Hz), 31.1 (CH , J(C,H) = 151.7 Hz), 46.9
(1.18 g, 5.83 mmol) was added to a 23.5 mL of a cooled (−78 °C) and
stirred 0.52 M solution of 1,4-dilithiobutane (12.22 mmol) in diethyl
ether. During the slow warmup procedure the starting materials
reacted and a LiCl-containing suspension formed. The precipitate was
removed by filtration, and 1.50 g (12,90 mmol) of TMEDA was added
to the filtrate. A second filtration and storage at −40 °C led to the
precipitation of 1.25 g of colorless crystals of 5 (56%), which were
collected on a Schlenk frit and dried in vacuo. This compound is
2
(
CH , br).
2
Synthesis of [(thf) Mg(μ-C H )] (2). 1,4-Dichlorobutane (6.4 g;
0.4 mmol) was added dropwise to a suspension of 3.0 g (112.4
mmol) of magnesium chips in 50 mL of THF; during this process
reaction heat evolved. After complete addition the reaction solution
was refluxed for an additional 3 h. All solids were removed by filtration,
and an aliquot was titrated with N/10 H SO against phenolphthalein
indicator, giving a yield of 80% with respect to starting 1,4-
dichlorobutane. Then 7.2 g (81.7 mmol) of 1,4-dioxane was added,
during which the solution was vigorously stirred, leading to a colorless
precipitate. The reaction mixture was heated nearly to the boiling
point of the solvent, and this hot mixture was filtered with a frit
covered with diatomaceous earth. The filter cake was washed twice
with 20 mL of hot THF. On the basis of the alkalinity of the unified
filtrates the yield was 60%. Due to the fact that the solution still
contained chloride, precipitation was repeated twice with 3.5 and 2 mL
of 1,4-dioxane. From the final filtrate 4.35 g of colorless pyrophoric
crystals (38%) was collected, which was nearly insoluble in THF at rt
but soluble at reflux temperature. Elemental analysis (C H MgO ,
2
4 8 ∞
5
2
4
extremely sensitive toward air and moisture. Elemental analysis
1
(C20
H48Li
MgN
, 382.8): found Mg 6.42, calcd 6.35. H NMR
2
4
(
200.1 MHz, [D ]THF): δ −0.90 (8H, t br, CH Mg), 1.68 (8H, br,
8
2
13 1
CH ), 2.16 (12H, s, NCH ), 2.31 (4H, s, NCH ). C{ H} NMR
2
3
2
(
5
50.3 MHz, [D ]THF): δ 7.8 (CH Mg), 34.1 (CH ), 46.1 (NCH ),
8 2 2 3
8.7 (NCH2).
Synthesis of [{(tmeda)Li} {(Ph) Mg(C H )] (6). A stirred
2
2
4
8
suspension of 1.70 g (6.37 mmol) of Ph Mg(diox) in 10 mL of
2
diethyl ether was cooled to 0 °C, and 12.5 mL (6.50 mmol) of a 0.52
M solution of 1,4-dilithiobutane was added at once. During this
process the magnesium complex dissolved, and thereafter a colorless
precipitate formed. This solid dissolved after addition of 1.65 g (14.2
mmol) of TMEDA. After filtration the filtrate was stored at 5 °C,
leading to 2.27 g of large colorless crystals of 6 (74%), which were
dried in vacuo to remove adherent solvent. Elemental analysis
12
24
2
2
24.6): found Mg 10.86, calcd Mg 10.82. Alkalinity: found 445.2 mg of
H SO /g (calcd 436.6 mg H SO /g). H NMR (200.1 MHz, 50 °C,
D ]THF): δ −0.63 (4H, t br, CH Mg), 1.68 (4H, t br, CH ).
C{ H} NMR (50.3 MHz MHz, 50 °C, [D ]THF): δ 7.7 (CH Mg),
1
2
4
2
4
[
8
2
2
1
1
3
1
(C H Li MgN , 480.8): found Mg 5.08, calcd Mg 5.05. H NMR
28
50
2
4
8
2
(
400.1 MHz, [D ]THF): δ −0.89 (1.6H, t br, CH Mg), −0.61 (2.4H,
8
2
3
5.1 (CH2).
t br, CH Mg), 1.69 (1.6H, t br, CH ), 2.00 (2.4H, t br, CH ), 2.12
2
2
2
Synthesis of [(thf) Mg(μ-(C(CH ) C H C(CH ) )] (3). A solution
2
3 2
2
4
3 2 2
(
24H, s, NCH ), 2.28 (8H, s, NCH ), 6.8−7.0 (6H, br, Ph), 7.92 (4H,
3
2
of 20.0 g (109 mmol) of 2,5-dichloro-2,5-dimethylhexane in 150 mL of
THF was slowly dropped over 5 h at rt into a suspension of 9.0 g (370
mmol) of magnesium turnings in 100 mL of THF. It is important that
during this reaction the temperature of the water cooling bath does
not exceed 30 °C. After complete addition the reaction mixture was
refluxed for an additional hour. Excess of magnesium was removed by
filtration, an aliquot of the filtrate was titrated with 0.1 N sulfuric acid,
and a yield of 53% was achieved. Thereafter, 25 mL (284 mmol) of
,4-dioxane was added to the vigorously stirred filtrate. The colorless
precipitate was removed by filtration, and the alkalinity of the filtrate
was determined via titration with 0.1 N sulfuric acid (yield: 41%). At
20 °C colorless crystals of [(thf) Mg(μ-C(CH ) C H C(CH ) ]
grew besides traces of a fine, colorless powder. The volume of the
mother liquor was reduced to a few milliliters, and a second crop of
crystals precipitated. The crystals were collected on a frit with large
pores in order to separate the cloudy mother liquor from the
crystalline material. Recrystallization from THF gave halide-free
crystals that easily lose coordinated thf, leading to dull crystals.
Therefore, the substance has to be stored in a freezer to minimize loss
of coordinated thf. Yield: 10.08 g (35.9%). Elemental analysis
C H Mg O , 561.4): found Mg 8.67, calcd Mg 8.66. Alkalinity:
found 448.7 mg H SO /g, calcd 449.3 mg H SO /g. H NMR (200.1
MHz, [D ]THF, rt): δ 0.86 (3H, s, CH , dimer), 0.90 (12H, s, CH ,
monomer), 0.98 (1H, s, CH , dimer), 1.02 (4H, s, CH , monomer).
13 1
Ph). C{ H} NMR (100.6 MHz, [D ]THF): δ 7.8 (CH Mg), 10.3
8
2
(
1
(
CH Mg), 34.1 (CH ), 34.7 (CH ), 46.1 (NCH ), 58.5 (NCH ),
2 2 2 3 2
22.9 (CH, br), 125.1 (CH), 125.9 (CH), 142.9 (CH, br), 143.9
13
CH), 172.8 (i-C), 179 (i-C, br). C NMR (100.6 MHz, [D ]THF):
8
1
1
13
1
1
13
δ 7.8 (t, J( H C) = 102.6 Hz, CH Mg), 10.3 (t, J( H C) = 103.2
2
1
1
13
1
1
13
Hz, CH Mg), 34.1 (t, J( H C) = 120.7 Hz, CH ), 34.7 (t, J( H C)
2
2
1
1
13
=
120.7 Hz, CH ), 46.1 (q, J( H C) = 134.1 Hz, NCH ), 58.5 (t,
2
3
1
1
13
1
1
13
J( H C) = 131.6 Hz, NCH ), 122.9 (d, J( H C) ≈ 158 Hz, br,
CH), 125.1 (d, J( H C) = 153.9 Hz, CH), 125.9 (d, J( H C) =
54.8 Hz, CH), 142.9 (d, br, CH), 143.9 (d, J( H C) = 153.9 Hz,
2
1
1
1
13
1
1
13
1
1
13
1
CH), 172.8 (s, i-C), 179 (br, i-C).
−
2 3 2 2 4 3 2 2
Structure Determinations. The intensity data for the compounds
were collected on a Nonius KappaCCD diffractometer using graphite-
monochromated Mo Kα radiation. Data were corrected for Lorentz
36,37
and polarization effects but not for absorption effects.
38
The structures were solved by direct methods (SHELXS ) and
2
refined by full-matrix least-squares techniques against Fo (SHELXL-
38
9
7 ). The hydrogen atoms of 1, 3_m1, and 6 were located by
difference Fourier synthesis and refined isotropically. All other
hydrogen atoms were included at calculated positions with fixed
thermal parameters. All nondisordered, non-hydrogen atoms were
(
32 64 2 4
1
38
2
4
2
4
refined anisotropically. The crystals of 4 were extremely thin and of
8
3
3
low quality, resulting in a substandard data set; however, the structure
is sufficient to show connectivity and geometry despite the high final R
value. We will publish only the conformation of the molecule and the
crystallographic data. We will not deposit the data in the Cambridge
Crystallographic Data Centre.
Crystallographic data as well as structure solution and refinement
details are summarized in Table S1 (see Supporting Information). XP
(SIEMENS Analytical X-ray Instruments, Inc.) was used for structure
representations.
2
2
1
3
1
C{ H} NMR (50.3 MHz, [D ]THF): δ 19.7 (C−Mg), 23.3 (C−
Mg), 33.5 (CH ), 34.5 (CH ), 50.8 (CH ), 53.4 (CH ). H NMR
200.1 MHz, [D ]THF, 50 °C): δ 0.86 (0.6H, s, CH ), 0.90 (14.4H, s,
8 3
CH ), 0.98 (0.2H, s, CH ), 1.02 (3.8H, s, CH ).
8
1
3
3
2
2
(
3
2
2
Synthesis of [Li(thf) ] [Mg (C H ) ] (4). A suspension of 1.52 g
4
2
3
4
8 4
(
7.51 mmol) of (thf) MgCl in 20 mL of THF was cooled to −78 °C,
1
.5
2
and then, 19.5 mL of a 0.52 M solution of 1,4-dilithiobutane (10.14
mmol) in diethyl ether was added. During a slow warmup of the
reaction mixture to 0 °C the substrates reacted and a LiCl-containing
suspension formed. Precipitated LiCl was removed by filtration, and
the solvent was distilled off the filtrate. The dry residue was dissolved
in THF and layered with n-heptane. At −40 °C colorless crystals of 4
grew, and a small amount of an oil separated from this two-phase
system. At rt the crystals melted, and therefore, exact determination of
the yield and accomplishment of elemental analysis were challenging.
ASSOCIATED CONTENT
Supporting Information
Crystallographic data (excluding structure factors) have been
deposited with the Cambridge Crystallographic Data Centre as
supplementary publications CCDC-900495 for 1, CCDC-
■
*
S
9
00496 for 2, CCDC-900497 for 3_m1, CCDC-900498 for
1
H NMR (200.1 MHz, rt, [D ]THF): δ −0.64 (8H, br, CH Mg), 1.73
3_m2, CCDC-900499 for 5, and CCDC-900500 for 6. Copies
of the data can be obtained free of charge on application to
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [e-mail:
8
2
1
(
(
8H, br, CH2). 13C{ H} NMR (50.3 MHz, rt, [D ]THF): δ 7.6
8
CH Mg), 34.0 (CH ).
2
2
7
584
dx.doi.org/10.1021/om300880f | Organometallics 2012, 31, 7579−7585