Hydrogallation of Trimethylsilylethynylbenzenes
Organometallics, Vol. 26, No. 9, 2007 2367
nPr2GaH,9 iPr2GaH,13 (Me3CCH2)2GaH,13 and tBu2GaH14 were
obtained according to literature procedures. Commercially available
1,4-(Me3Si-CtC)2C6H4 was thoroughly evacuated prior to use.
1,3,5-(Me3Si-CtC)3C6H3 was obtained according to a standard
procedure;15 experimental details are given below. Only the most
intensive peaks of the mass spectra were given; the complete
isotopic patterns are in accordance with the calculated ones. The
assignment of the NMR spectra is based on HMBC, HSQC,
ROESY, and DEPT135 data.
29Si NMR (C6D6, 79.5 MHz): δ -7.0. IR (CsBr plates, paraffin,
cm-1): 1607 w, 1578 m, 1541 m phenyl, ν(CdC); 1458 vs
(paraffin); 1420 m δ(CH3); 1375 vs (paraffin); 1340 w, 1301 w,
1257 sh, 1246 vs δ(CH3); 1198 w, 1163 w δ(CH); 1094 w, 1051
w, 1034 w, 999 sh, 986 s, 966 sh ν(CC); 933 vw, 906 sh, 864 vs,
837 vs, 777 vw F(CH3(Si)); 748 m, 725 m (phenyl, paraffin); 691
m νas(SiC); 652 m νs(SiC); 563 s, br, 546 sh, 517 sh, 433 w ν-
(GaC), δ(CC). MS (EI, 70 eV) (%): 497 (1.2), 499 (1.5), 501 (1.0)
M+ - Et; 371 (52.3), 373 (37.1) M+ - GaEt2 - ethene; 127 (87),
129 (68) GaEt2.
Synthesis of 1,3,5-(Me3Si-CtC)3C6H3. 1,3,5-Tribromobenzene
(9.670 g, 30.7 mmol) was dissolved in 250 mL of diethylamine.
Copper(I) iodide (0.050 g, 0.26 mmol) and dichlorobis(tri-
phenylphosphino)palladium(II) (0.40 g, 0.57 mmol) were added at
room temperature. Dropwise addition of trimethylsilylethyne (10.85
g, 110.5 mmol) caused a color change from yellow to dark green
and brown (the solvent and all reagents were employed as
purchased). The mixture was heated to 70 °C for 7 h, which resulted
in the precipitation of a brown solid. After cooling to room
temperature the solid was filtered off and washed with few milliliters
of diethyl ether. All volatiles of the filtrate were removed in vacuum.
The residue was dissolved in n-pentane and purified by column
chromatography (Al2O3). The solvent was removed in vacuum, and
the residue was thoroughly evacuated to 10-3 Torr to yield a light
yellow powder of the product. Yield: 11.00 g (97%). Mp (argon,
sealed capillary): 67-68 °C. Anal. Calcd [C21H30Si3] (366.7): C,
68.78; H, 8.25. Found: C, 68.6; H, 8.2. 1H NMR (C6D6, 400
MHz): δ 7.53 (3 H, s, phenyl), 0.19 (27 H, s, SiMe3). 13C NMR
(C6D6, 100 MHz): δ 135.3 (C-H of phenyl), 124.4 (ipso-C of
phenyl), 103.8 (CtC-Ph), 95.9 (1JC-Si ) 82.7 Hz, CtC-Si), -0.1
(1JC-Si ) 56.4 Hz, SiMe3). 29Si NMR (C6D6, 79.5 MHz): δ -17.6.
IR (KBr, neat, cm-1): 2958 vs, 2898 s (νCH3); 2166 vs, 2139 m
ν(CtC); 1580 s phenyl; 1410 vs, 1250 vs δ(CH3); 1162 vs, 981
vs ν(CC); 882 sh, 846 vs, 759 vs, 700 m F(CH3(Si)); 680 s νas-
(SiC); 651 s νs(SiC). MS (EI, 25 eV) (%): 366 (100) M+; 351
(64) M+ - Me.
Hydrogallation of 1,4-Bis- and 1,3,5-Tris(trimethylsilylethy-
nyl)benzene: General Procedure. A solution of the respective
dialkylgallium hydride in n-hexane (1.3 to 3.4 mmol in 20 mL)
was treated with a solution of the stoichiometric quantity of the
corresponding bis- or trisalkyne (molar ratios 2:1 or 3:1) in n-hexane
(0.6 to 1.1 mmol in 20 mL) at room temperature. An excess of the
hydride was applied for the synthesis 5a (50%), 5b (10%), 5d
(100%), and 7a (10%). The solutions were heated under reflux for
15 to 20 h and filtered after cooling to room temperature because
small quantities of colorless, unknown solids precipitated in some
cases. Owing to partial decomposition, elemental gallium precipi-
tated from the reaction of the relatively unstable diethylgallium
hydride with the dialkyne (syntheses of 5a). The filtrates were
concentrated in vacuum at room temperature to a few milliliters
and cooled to -80 °C to get the colorless, solid products. Only
compound 5a did not give a solid product under these conditions.
Characterization of the Bisalkenyl Compound 5b (GanPr2).
Yield: 59%. Mp: slightly above -80 °C; oily liquid at room
temperature. Anal. Calcd for 5b [C28H52Si2Ga2] (584.3): C, 57.56;
1
H, 8.97; Ga, 23.86. Found: C, 57.6; H, 8.9; Ga, 23.9. H NMR
3
(C6D6, 400 MHz): δ 7.80 (2 H, s, CdC-H; JSiH ) 11.7 Hz),
6.93 (4 H, s, phenyl), 1.60 (8 H, pseudosextet, CH2CH3), 1.02 (12
3
3
H, t, JHH ) 7.6 Hz, Me of nPr), 0.84 (8 H, br, t, JHH ) 7.6 Hz,
GaCH2), 0.23 (18 H, s, SiMe3). 13C NMR (C6D6, 100 MHz): δ
168.9 (C ) C(Si)Ga), 149.0 (CdC(Ga)Si), 144.9 (ipso-C of phenyl),
126.4 (C-H of phenyl), 23.1 (GaCH2), 20.0 (CH2CH3), 19.6 (Me
of nPr), 0.0 (SiMe3). 29Si NMR (C6D6, 79.5 MHz): δ -7.0. IR
(CsBr plates, paraffin, cm-1): 1603 m, 1568 s, 1558 s, 1495 s
phenyl, ν(CdC); 1464 vs (paraffin); 1454 vs, 1412 s, 1394 m δ-
(CH3); 1373 s (paraffin); 1329 s, 1246 vs δ(CH3); 1209 vw, 1194
w, 1180 w δ(CH); 1103 w, 1057 vs, 1015 m, 986 vs ν(CC); 912
vs, 887 vs, 835 vs, 794 w F(CH3(Si)); 748 s, 720 w (phenyl,
paraffin); 687 s νas(SiC); 650 m, 619 s νs(SiC); 538 s, br., 490 m,
430 m ν(GaC), δ(CC). MS (EI, 70 eV) (%): 539 (0.6), 541 (0.8),
543 (0.4) M+ - nPr; 427 (3.2), 429 (4.4) M+ - GanPr2; 155 (100),
157 (67) GanPr2.
Characterization of the Bisalkenyl Compound 5c (GaiPr2).
Yield: 66%. Mp (argon, sealed capillary): 32 °C. Anal. Calcd for
5c [C28H52Si2Ga2] (584.3): C, 57.56; H, 8.97; Ga, 23.86. Anal.
1
Found: C, 57.6; H, 9.0; Ga, 24.1. H NMR (C6D6, 400 MHz): δ
3
7.82 (2 H, s, CdC-H; JSiH ) 11.4 Hz), 6.90 (4 H, s, phenyl),
3
1.23 (24 H, d, JHH ) 6.8 Hz, Me of iPr), 1.14 (4 H, m, GaCH),
0.22 (18 H, s, SiMe3). 13C NMR (C6D6, 100 MHz): δ 168.0 (C )
C(Si)Ga), 149.4 (CdC(Ga)Si), 145.4 (ipso-C of phenyl), 126.0
(C-H of phenyl), 20.9 (Me of iPr), 20.8 (GaCH), 0.0 (SiMe3).
29Si NMR (C6D6, 79.5 MHz): δ -7.3. IR (CsBr plates, paraffin,
cm-1): 1556 s, 1495 m phenyl, ν(CdC); 1463 vs (paraffin); 1402
w δ(CH3); 1378 s (paraffin); 1347 w, 1316 w, 1245 vs δ(CH3);
1214 w, 1153 w δ(CH); 1116 s, 1074 w, 1012 w, 985 s, 950 s
ν(CC); 918 s, 887 s, 834 vs F(CH3(Si)); 749 m, 734 w (phenyl,
paraffin); 688 w νas(SiC); 619 w, 593 w νs(SiC); 523 m, br, 432 m
ν(GaC), δ(CC). MS (EI, 70 eV) (%): 539 (42), 541 (64), 543 (24)
M+ - iPr; 497 (7), 499 (10), 501 (5) M+ - nPr - propene; 155
(100), 157 (74) GaiPr2.
Characterization of the Bisalkenyl Compound 5d [Ga-
(CH2tBu)2]. Yield: 36%; recrystallization from n-hexane after
removal of trineopentylgallium at 55 °C and 10-3 Torr (yield: 0.34
g of trineopentylgallium related on a starting quantity of 0.87 g of
dineopentylgallium hydride). Mp (argon, sealed capillary): 92-
94 °C. Anal. Calcd for 5d [C36H68Si2Ga2] (696.6): C, 62.07; H,
9.84; Ga, 20.02. Anal. Found: C, 62.3; H, 9.8; Ga, 19.8. 1H NMR
Characterization of the Bisalkenyl Compound 5a (GaEt2).
This compound could not be purified by recrystallization. An oily,
liquid product resulted at room temperature that had some unknown
impurities (about 20%). The NMR, IR, and mass spectroscopic
characterization was done with the raw product of the reaction,
1
but we did not carry out elemental analyses. H NMR (C6D6, 400
3
(C6D6, 400 MHz): δ 7.76 (2 H, s, CdC-H; JSiH ) 11.7 Hz),
MHz): δ 7.82 (2 H, s, CdC-H), 6.86 (4 H, s, phenyl), 1.17 (12
H, t, 3JHH ) 8.0 Hz, Me of Et), 0.74 (8 H, t, 3JHH ) 8.0 Hz, GaCH2),
0.21 (18 H, s, SiMe3). 13C NMR (C6D6, 100 MHz): δ 168.3 (Cd
C(Si)Ga), 149.2 (CdC(Ga)Si), 145.3 (ipso-C of phenyl), 126.2
(C-H of phenyl), 11.3 (GaCH2), 10.1 (Me of Et), -0.17 (SiMe3).
7.00 (4 H, s, phenyl), 1.13 (8 H, s, Ga-CH2), 1.07 (36 H, s, CMe3),
0.28 (18 H, s, SiMe3). 13C NMR (C6D6, 100 MHz): δ 169.7 (Cd
C(Si)Ga), 149.2 (CdC(Ga)Si), 143.9 (ipso-C of phenyl), 127.1
(C-H of phenyl), 41.9 (Ga-CH2), 34.2 (CMe3), 31.9 (GaCMe3),
0.7 (SiMe3). 29Si NMR (C6D6, 79.5 MHz): δ -6.8. IR (CsBr plates,
paraffin, cm-1): 1556 m, 1495 m phenyl, ν(CdC); 1462 vs
(paraffin); 1400 w δ(CH3); 1377 s (paraffin); 1362 s, 1346 w, 1261
m, 1244 s δ(CH3); 1169 vw, 1136 w, 1101 w, 1061 w, 1015 w,
1003 m, 988 w ν(CC); 918 s, 891 s, 835 vs F(CH3(Si)); 748 s, 721
m (phenyl, paraffin); 685 m νas(SiC); 619 m νs(SiC); 590 vw, 559
(14) Uhl, W.; Cuypers, L.; Graupner, R.; Molter, J.; Vester, A.;
Neumu¨ller, B. Z. Anorg. Allg. Chem. 2001, 627, 607.
(15) (a) Weber, E.; Hecker, M.; Koepp, E.; Orlia, W; Czugler, M.;
Cso¨regh, I. J. Chem. Soc., Perkin Trans. 2 1988, 1251. (b) Mongin, O.;
Papamicael, C.; Hoyler, N.; Grossauer, A. J. Org. Chem. 1998, 63, 5568.