W. Uhl et al. · The Methylene-bridged Dialuminium Compound R2Al-CH2-AlR2 [R = CH(SiMe3)2]
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3.23 (sep, 4 H, JH−H = 7.1 Hz, o-CHMe2) 2.77 (sep, 2 H, (79.5 MHz, [D8]THF): δ = −2.3. – 7Li NMR (155.5 MHz,
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3JH−H = 7.0 Hz, p-CHMe2), 1.26 (d, 24 H,3JH−H = 7.1 Hz, [D8]THF): δ = −0.3.
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o-CHMe2), 1.21 (d, 12 H, JH−H = 7.0 Hz, p-CHMe2). –
Synthesis of [K(18-crown-6)(OEt2)][{(Me3Si)2CH}2Al-
13C NMR (100 MHz, C6D6): δ = 156.3 (o-C), 151.0 (p-
CH2-Al{CH(SiMe3)2}2(µ-ClO4)] (3c(OEt2))
C), 139.1 (ipso-C), 120.6 (m-C), 40.2 (o-CHMe2), 34.4 (p-
CHMe2), 24.8 (o-CHMe2), 23.7 (p-CHMe2). – MS (EI,
20 eV, 413 K): m/z (%) = 468 (20) [M]+, 264 (68) [M–
C6H3(2,4,6-i-Pr)3–H]+.
A solution of 1a (0.666 g, 0.95 mmol) in Et2O (15 mL)
was added quickly by means of a pipette to a suspension
of KClO4 (0.262 g, 1.89 mmol) and 18-crown-6 (0.250 g,
0.95 mmol). The colour of the reaction mixture changed
from colourless to pale yellow. Stirring was continued for
18 h. The suspension was filtered, the filtrate was con-
centrated and kept at 2 ◦C to yield colourless crystals of
3c(OEt2). Yield: 0.387 g (35%); m. p. (under argon; sealed
capillary): 142 ◦C (dec.). – IR (CsI, paraffin): ν = 1466 vs,
1454 vs, 1377 s (paraffin), 1352 w, 1248 s δ(CH3), 1117 m
νas(ClO4), 1007 w δ(CHSi2), 962 vw, 937 vw νs(ClO4), 926
vw, 918 vw, 843 vs, 777 w, 752 w ρ(CH3(Si), 723 w (paraf-
fin), 671 w, 611 vw ν(SiC), 563 vw, 501 vw cm−1 ν(AlC),
ν(AlO). – 1H NMR (400 MHz, [D8]THF): δ = 3.61 (s, 24
Synthesis of [Li(TMEN)2][{(Me3Si)2CH}2Al-CH2-
Al{CH(SiMe3)2}2(µ-Cl)] (3a)
A solution of 1a (0.512 g, 0.73 mmol) was added at
room temperature to a suspension of anhydrous LiCl
(0.031 g, 0.73 mmol) in Et2O (20 mL) and TMEN (0.44 mL,
2.93 mmol). After the solution had been stirred for 18 h at
room temperature, a colourless, voluminous precipitate had
formed that was filtered and recrystallised from Et2O to yield
colourless crystals of 3a. Yield: 0.627 g (88%); m. p. (under
argon; sealed capillary): 146 ◦C (dec.). – IR (CsI, paraffin):
ν = 1458 vs, 1377 vs (paraffin), 1309 w, 1290 w, 1242 m
δ(CH3), 1182 w, 1157 w, 1128 w, 1098 w (TMEN), 1069
w, 1030 w ν(CN), ν(CC), 1015 w δ(CHSi2), 984 w, 920 w,
845 m, 748 w ρ(CH3(Si)), 721 w (paraffin), 669 w, 633 w,
610 vw νSiC, 557 w, 509 w, 474 w, 463 w, 437 w cm−1
ν(AlC), ν(AlCl), ν(LiN). – 1H NMR (400 MHz, [D8]THF):
δ = 2.30 (s, 8 H, NCH2), 2.15 (s, 24 H, NMe), 0.12 (s, 76
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H, OCH2), 3.38 (q, 4 H, JH−H = 7.0 Hz, OCH2, Et2O),
1.10 (t, 3JH−H = 7.0 Hz, CH3, Et2O), 0.12 (s, 76 H, SiMe3),
−1.03 (s, 4 H, CHSi), −1.28 (s, 2 H, AlCH2Al). – 13C NMR
(100 MHz, [D8]THF): δ = 71.1 (OCH2, crown ether), 66.3
(OCH2, Et2O) 16.4 (CH3, Et2O), 5.9 (SiMe3), 5.1 (CHSi),
2.8 (br., AlCH2Al). – 29Si NMR (79.5 MHz, [D8]THF): δ =
−2.3.
H, SiMe3), −0.83 (s, 2 H, AlCH2Al), −0.92 (s, 4 H, CHSi). Synthesis of [Li(TMEN)2][{(Me3Si)2CH}2Al-CH2-
–
13C NMR (100 MHz, [D8]THF): δ = 58.9 (NCH2), 46.2 Al{CH(SiMe3)2}2(µ-N(H)i-Pr)] (3d)
(NMe), 11.5 (br., AlCH2Al), 6.1 (SiMe3), 6.06 (CHSi). –
29Si NMR (79.5 MHz, [D8]THF): δ = −2.3. – 7Li NMR
(155.5 MHz, [D8]THF): δ = 0.2.
A solution of H2N(i-Pr) (0.042 g, 0.061 mL, 0.71 mmol)
in Et2O (10 mL) was treated with n-BuLi (0.441 mL,
0.71 mmol, 1.6 M in n-hexane) and stirred for 16 h at room
temperature. Upon addition of TMEN (0.5 mL, 3.3 mmol)
and a solution of 1a (0.498 g, 0.71 mmol) in n-pentane
(20 mL) pure 3d precipitated as a colourless solid and
Synthesis of [Li(TMEN)2][{(Me3Si)2CH}2Al-CH2-
Al{CH(SiMe3)2}2(µ-Br)] (3b)
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was isolated. Yield: 0.504 g (71%). – H NMR (400 MHz,
Compound 3b was obtained in an analogous manner to
compound 3a by stirring a mixture of 1a (0.69 g, 0.98 mmol),
anhydrous LiBr (0.086 g, 0.99 mmol) and TMEN (0.45 mL,
3.00 mmol) in Et2O (20 mL) for 18 h at room tempera-
ture. Recrystallisation of the crude product gave colourless
crystals of 3b. Yield: 0.789 g (79%); m. p. (under argon;
sealed capillary): 158 – 168 ◦C (dec.). – IR (CsI, paraffin):
ν = 1452 m, 1375 w (paraffin), 1288 m, 1240 m δ(CH3),
1182 w, 1157 m, 1128 m, 1098 w (TMEN), 1069 w ν(CN),
ν(CC), 1020 m δ(CHSi2), 947 w, 922 vw, 845 s, 775 vw,
748 vw ρ(CH3(Si), 719 w (paraffin), 667 w, 625 w νSiC,
588 w, 554 vw, 527 vw, 509 w, 453 w, 442 w cm−1 ν(AlC),
ν(AlBr), ν(LiN). – 1H NMR (400 MHz, [D8]THF): δ = 2.30
[D8]THF): δ = 3.53 (m, br., 1 H, NCH), 2.31 (s, 8 H,
NCH2), 2.15 (s, 24 H, NMe), 1.29 (d, 6 H, 3JH−H = 6.4 Hz,
CHMe), 0.15 (s, 76 H, SiMe3), −1.06 (s, 6 H, CHSi
and AlCH2Al); NH not detected. – 13C NMR (100 MHz,
[D8]THF): δ = 58.9 (NCH2), 46.2 (NMe), 45.7 (NCH), 30.6
(CHMe2), 17.5 (br., AlCH2Al), 6.8 (SiMe3), 5.1 (CHSi). –
29Si NMR (79.5 MHz, [D8]THF): δ = −2.7. – 7Li NMR
(155.5 MHz, [D8]THF): δ = −0.5.
Synthesis of [Li(DME)3][{(Me3Si)2CH}2Al-CH2-
Al{CH(SiMe3)2}2(µ-N(H)i-Pr)] (3e)
Recrystallisation of 3d in DME yielded 3e as colourless
(s, 8 H, NCH2), 2.14 (s, 24 H, NMe), 0.14 (s, 76 H, SiMe3), crystals. – IR (KBr, paraffin): ν = 1601 w δ(NH), 1462
−0.63 (s, 2 H, AlCH2Al), −0.83 (s, 4 H, CHSi). – 13C vs, 1377 vs (paraffin), 1288 m, 1238 s δ(CH3), 1179 m,
NMR (100 MHz, [D8]THF): δ = 58.9 (NCH2), 46.2 (NMe), 1159 m, 1128 m, 1096 w, 1069 vw ν(CN), ν(CC), 1013 s
13.7 (br., AlCH2Al), 6.3 (CHSi), 6.2 (SiMe3). – 29Si NMR δ(CHSi2), 972 vw, 947 m, 922 m, 843 s, 775 w ρ(CH3(Si)),
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