4542 Organometallics, Vol. 19, No. 22, 2000
Uhl et al.
hydride,26 dimethylaluminum bromide,26 and the carbaalane
26 were synthesized according to literature procedures. Com-
mercially available n-butyllithium (Chemetall) was used with-
out further purification; propyne (Lancaster) was dried over
P4O10 prior to use. NMR spectra were recorded on a 500 MHz
NMR spectrometer at 300 K. The resonances were assigned
on the basis of 1H, 13C, H-H-COSY, HMQC, and HMBC
spectra; shifts are reported on the δ scale relative to residual
nondeuterated solvent signals as internal standard.
C), 129.34 (o-C), 129.30 (m-C), 126.0 (p-C), 36.0 (CH2); benzyl
groups at C(11), C(31), C(51), and C(61): 147.5 (i-C), 129.5
(o-C), 128.8 (m-C), 126.3 (p-C), 36.2 (CH2); phenylethynyl
group, 165.9 (i-C), 132.9 (o-C), 129.3 (m-C), 134.0 (p-C), 117.0
(C(42)), 89.5 (C(41)); methyl groups at Al(1), Al(2), Al(5), and
Al(6), -10.9; methyl groups at Al(3), Al(4), Al(7), and Al(8):
-8.1; cluster carbon atoms, 35.1 (C(11), C(31), C(51), C(61)),
20.9 (C(21)). IR (CsBr plates, paraffin; cm-1): 1977 w, 1957
m (ν(CtC)); 1865 vw, 1799 vw, 1597 m, 1590 m, 1580 w
phenyl; 1489 m; 1456 vs, 1377 vs paraffin; 1301 m, 1184 s,
1092 vw, 1072 w, 1028 w, 978 m, 953 vs, 923 m, 905 s, 820 s
(ν(CC), δ(CH3), δ(CH2)); 750 vs, 706 vs, 688 vs, 659 vs, 580 s,
568 s, 552 s, 533 m, 513 m (δ(CC), δ(phenyl), ν(AlC)); 447 w,
422 m, 337 w, 291 w (ν(AlC)). UV/vis (n-hexane; λmax, nm (log
ꢀ)): 250 (3.8), 380 (sh, 3.3).
Syn th esis of th e Ca r ba a la n e (AlEt)8(CCH2C6H5)5H (4).
The orange-red cluster compound 2 (0.279 g, 0.308 mmol) was
treated with a large excess of diethylaluminum hydride (2 mL,
1.62 g, 18.8 mmol) in the absence of solvent. The mixture was
heated at 60 °C for 18 h. The color changed to yellow, and a
colorless solid precipitated. All volatile components (excess
hydride, triethylaluminum) were distilled off, and the residue
was recrystallized from n-pentane (20/-30 °C). Yield: 0.206
g (69%), air-sensitive solid. Dec pt (argon, sealed capillary):
124 °C. Anal. Calcd for C56H76Al8 (965.07): Al, 22.4. Found:
Al, 22.0. Molar mass (cryoscopically in benzene): 930. 1H NMR
(C6D6, 500 MHz; δ): benzyl group at C(500), 7.63 (2 H, m, o-H),
7.36 (2 H, m, m-H), 7.22 (1 H, m, p-H), 3.84 (2 H, s, CH2);
benzyl groups at C(100)-C(400), 7.28 (8 H, m, o-H), 7.21 (8
H, m, m-H), 7.09 (4 H, m, p-H), 3.39 (8 H, s, CH2); ethyl groups
Syn th esis of Me2AlCtCMe. A mixture of 15 mL of a
solution of n-butyllithium in n-hexane (1.6 M, 24.0 mmol) and
20 mL of n-pentane was cooled to -70 °C. Dried (P4O10
)
gaseous propyne was passed over the stirred solution for 30
min, and the precipitation of a solid showed the beginning of
the reaction. The suspension was warmed to room temperature
and stirred until the evolution of gas (excess of propyne,
butane) stopped. A solution of dimethylaluminum bromide
(3.00 g, 21.9 mmol) in 20 mL of n-pentane was added at room
temperature. The mixture was stirred for 3 h and filtered.
Colorless and very air-sensitive crystals of the product were
isolated after concentration of the solution to about 10 mL and
cooling to -50 °C. Yield: 1.957 g (93%). Mp (argon, sealed
capillary): 48 °C. Anal. Calcd for C5H9Al (96.1): Al, 0.28.
Found: Al, 0.27. 1H NMR (C6D6, 300 MHz; δ): 1.12 (3 H, s,
C-CH3), -0.15 (6 H, s, Al-CH3). 13C NMR (C6D6, 75.5 MHz;
δ): 133.4 (ethynyl), the second resonance was not observed,
5.2 (C-CH3), -7.8 (br, Al-CH3). IR (CsBr plates, paraffin;
cm-1): 2152 vw, 2109 vs (ν(CtC)); 1948 w, 1867 w, 1762 w;
1456 vs, 1377 vs (paraffin); 1305 m, 1249 w, 1190 vs, 1012 m,
974 vs, 903 m (ν(CC), δ(CH3)); 696 vs, br, 571 s (δ(CC), δ(CH3),
ν(AlC)); 472 m, 393 s, 343 vs (ν(AlC)).
3
at Al(1)-Al(4), 1.10 (12 H, t, J HH ) 8.1 Hz, CH3), 0.10 (8 H,
3
q, J HH ) 8.1 Hz, CH2); ethyl groups at Al(5)-Al(8), 1.36 (12
3
3
H, t, J HH ) 8.1 Hz, CH3), 0.51 (8 H, q, J HH ) 8.1 Hz, CH2);
5.28 (1 H, s, AlH). 13C NMR (C6D6, 125.8 MHz; δ): benzyl group
at C(500), 148.0 (i-C), 129.3 (o-C), 129.0 (m-C), 126.4 (p-C),
35.5 (CH2); benzyl groups at C(100)-C(400), 147.9 (i-C), 129.8
(o-C), 128.4 (m-C, covered by solvent), 126.7 (p-C), 34.7 (CH2);
ethyl groups at Al(1)-Al(4), 10.5 (CH3), 1.9 (CH2); ethyl groups
at Al(5)-Al(8), 10.4 (CH3), 2.7 (CH2); 31.3 (C(100)-C(400)),
23.9 (C(500)). IR (CsBr plates, paraffin; cm-1): 1940 vw, 1867
vw, 1824 vw, 1769 vw, 1597 m phenyl; 1463 vs, 1403 m, 1377
vs paraffin; 1295 m (ν(AlH)(?)); 1226 w, 1189 vw, 1171 w, 1153
w, 1074 w, 1048 vw, 1030 w, 991 m, 959 s, 900 m, 822 m
(ν(CC), δ(CH3), δ(CH2)); 747 vs, 701 vs, 673 vs, 641 s, 617 s,
594 s, 560 m, 502 m (δ(CC), δ(phenyl), ν(AlC)); 451 vw, 428
w, 414 w, 355 w (ν(AlC)). UV/vis (n-hexane; λmax, nm (log ꢀ)):
250 (3.9).
Syn th esis of th e Ca r ba a la n e (AlMe)7(CCH2CH3)4H2 (6).
Dimethylpropynylaluminum (0.604 g, 6.29 mmol) was dis-
solved in 2.3 g (39.7 mmol) of dimethylaluminum hydride, and
the mixture was stirred at room temperature for 2 h. A
colorless product precipitated. All volatile components were
removed under vacuum. The residue was dissolved in 40 mL
of toluene and cooled to -30 °C. An amorphous and highly
pyrophoric solid was isolated in a yield of 0.201 g (29%), which
probably contains the arachno cluster (AlMe)8(CCH2CH3)5H.
The mother liquor was evaporated, the residue was dissolved
in 10 mL of cyclopentane, and this solution was cooled to -30
°C to obtain colorless, pyrophoric crystals of 6. Yield: 0.455 g
(63%). Dec pt (argon, sealed capillary): 274 °C. Anal. Calcd
for C19H43Al7 (460.42): Al, 41.0. Found: Al, 40.8. Molar mass
(cryoscopically in benzene): 490. 1H NMR (C6D6, 500 MHz;
Ra m a n Sp ectr u m of th e Ca r ba a la n e (AlMe)8(CCH2-
C6H5)5H (1). Single crystals, excitation 647.1 nm, cm-1: 1599
s, 1580 w (ν(CC) phenyl); 1491 vw, 1452 w, 1444 w, 1424 vw
(δ(CH2), δ(CH3)); 1331 vw, 1300 w, 1206 w (δ(CH) benzyl); 1203
w (δs(CH3(Al)); 1186 w, 1181 w (δ(CH) benzyl); 1158 vw, 1152
vw (δ(CH2) benzyl); 1029 (ν(CH2) phenyl); 1002 s, 988 vw, 963
vw, 952 vw (ν(CC) phenyl); 931 vw, 908 vw, 883 w (δ,γ(CH)
benzyl); 822 m; 749 vw (F(CH2), γ(CH) benzyl); 710 vw (F(CH3-
(Al))); 686 w, 673 vw, 660 vw (δ,γ(CC) pheny)l; 628 w (ν(AlC));
620 m, 582 vw, 551 m, 525 w, 515 w (δ(CC) phenyl); 442 vw,
428 w, 369 vw, 345 w (γ(CC) phenyl); 325 s, 305 m, 292 m
(ν(breathing) cluster); 246 vw, 234 vw; 212 w, 195 w, 129 m
(δ(cluster)).
Syn th esis of th e Ca r ba a la n e (AlMe)8(CCH2C6H5)5(Ct
CC6H5) (5). Dimethyl(phenylethynyl)aluminum (0.472 g, 2.99
mmol) was treated with 0.346 g (5.97 mmol) of dimethyl-
aluminum hydride. The mixture was heated at 60 °C for 24 h.
All volatile components were removed under vacuum. The
residue was recrystallized from toluene (20/-50 °C). Yield:
0.189 g (40%), moderately air-stable red solid. Dec pt (argon,
sealed capillary): 204 °C. Anal. Calcd for C56H64Al8 (952.98):
Al, 22.7. Found: Al, 22.4. 1H NMR (C6D6, 500 MHz; δ): benzyl
group at C(21), 7.50 (2 H, m, o-H), 7.36 (2 H, m, m-H), 7.22 (1
H, m, p-H), 3.52 (2 H, s, CH2); benzyl groups at C(11), C(31),
C(51), and C(61), 7.26 (8 H, m, o-H), 7.21 (8 H, m, m-H), 7.09
(4 H, m, p-H), 3.24 (8 H, s, CH2); phenylethynyl group, 7.34 (2
H, m, o-H), 6.65 (2 H, m, m-H), 6.77 (1 H, m, p-H); methyl
groups at Al(1), Al(2), Al(5) ,and Al(6), -0.33 (12 H, s); methyl
groups at Al(3), Al(4), Al(7), and Al(8), -0.48 (12 H, s). 13C
NMR (C6D6, 125.8 MHz; δ): benzyl group at C(21), 148.5 (i-
3
δ): ethyl groups at C(11) and C(11′), 2.01 (4 H, q, J HH ) 7.3
3
Hz, CH2), 1.03 (6 H, t, J HH ) 7.3 Hz, CH3); ethyl groups at
3
C(21) and C(21′), 1.99 (4 H, q, J HH ) 7.3 Hz, CH2), 1.12 (6 H,
3
t, J HH ) 7.3 Hz, CH3); methyl groups, -0.10 (6 H, s, Al(1)
and Al(1′)), -0.24 (12 H, s, Al(2), Al(2′), Al(4), and Al(4′)), -0.40
(3 H, s, Al(3)); 4.91 (2 H, s, AlH). 13C NMR (C6D6, 125.8 MHz;
δ): ethyl groups at C(11) and C(11′), 23.6 (CH2), 23.5 (CH3);
ethyl groups at C(21) and C(21′), 21.6 (CH2), 23.7 (CH3); cluster
carbon atoms, 15.4 (C(11) and C(11′)), 26.1 (C(21) and C(21′));
methyl groups, -8.5 (C(1), C(1′)), -15.0 (C(2), C(2′), C(4), and
C(4′)), -20.2 (Al(3)). IR (CsBr plates, paraffin; cm-1): 1321 s,
1310 s, 1277 m, 1260 m, 1207 sh br (ν(AlH)(?)), 1189 vs, 1134
s br (ν(AlH)(?)), 1092 s, 1067 s, 1046 s, 1018 s, 897 s, 878 vs,
848 s br (δ(AlH)(?)), 794 vs (ν(CC), δ(CH3), δ(CH2)); 719 vs,
683 vs, 659 vs br (δ(CC), ν(AlC)); 462 m, 427 m, 409 m, 391
m, 363 m, 337 m (ν(AlC)). Raman spectrum (single crystals,
excitation 647.1 nm; cm-1): 1472 w (ν(AlHAl)(?)); 1444 m (δas-
(CH3(Al)); 1372 (δ(CH2)); 1191 s, 1181 m (δs(CH3)); 1067 w,
1054 m, 1019 m (δ(CH3), ν(CC)); 897 vw, 881 vw (δ,F(CH2));