Reactions of the alkynes with dialkylgallium hydrides—general
procedure
(ipso-C of phenyl), 122.1 (ortho-C of phenyl), 36.9 (CMe3), 32.0
(CMe3), 21.4 (Me of isopropyl), 17.9 (GaCH). IR (CsBr plates,
−1
=
paraffin, cm ): 1674 m, 1590 sh, 1568 vs mC C, phenyl; 1455 vs,
A solution of the dialkylgallium hydride in n-hexane (2 to 6 mmol
in 25 ml) was added to a solution of the respective bis- or
trisalkyne in the same solvent (about 1 to 2 mmol in 25 ml) at
room temperature. While usually the exact stoichiometric ratios
of the starting compounds were applied, an excess of 5% of
the hydride was employed in all reactions of di(n-propyl)gallium
hydride. The solutions were heated under reflux for 16 h and
filtered because small quantities of colorless, unknown solids
preciptated in some cases. The filtrates were concentrated under
vacuum at room temperature to a few ml. In some cases the
products precipitated directly, while in others cooling to down
to −80 ◦C was required to get the solid products. Compound
4b could be recrystallized with some difficulties from n-pentane
only. Owing to the NMR spectroscopic characterization of the
raw products the compounds were formed almost quantitatively.
However, precipitation from the solutions as solids or the complete
removal of the trialkylgallium derivatives proved to be difficult.
Thus, very low yields of the pure products were obtained in a few
cases.
1377 vs paraffin; 1310 w, 1256 w, 1246 w dCH3; 1225 m, 1202 s,
1153 w, 1122 w, 1025 m, 970 s, 911 m, 873 m, 837 w mCC, dCH3,
phenyl; 723 m paraffin; 709 s, 595 s, 539 s, 457 m, 433 m mGaC.
Characterization of the [3,3,3]-cyclophane 2e (R = tBu). Yield:
10% of pure 2e after twofold recrystallization; the complete
removal of the by-product tri(tert-butyl)gallium was extremely
difficult. Decomp. (argon, sealed capillary): above 210 ◦C. 1H
NMR (C6D6, 400 MHz): d = 6.41 (6 H, s, C6H3), 5.94 (6 H, s,
=
=
C C–H), 1.42 (27 H, s, GaCMe3), 1.12 (54 H, s, C C–CMe3).
13
=
C NMR (C6D6, 100 MHz): d = 152.4 (Ga–C C–H), 152.3 (Ga–
=
C C–H), 145.7 (ipso-C of phenyl), 122.6 (ortho-C of phenyl), 36.9
(CMe3 of ethenyl), 31.9 (CMe3 of ethenyl), 30.9 (Ga–CMe3), 28.7
(br., Ga–CMe3). IR (CsBr plates, paraffin, cm−1): 1578 vs, 1557
=
vs mC C, phenyl; 1454 vs paraffin; 1402 m dCH3; 1377 s paraffin;
1366 s, 1330 vw, 1310 vw, 1274 vw, 1253 w dCH3; 1225 m, 1202 s,
1179 m, 1134 m, 1119 m, 1105 m, 1037 m, 1026 m, 989 m, 977 m,
910 m, 896 w, 879 w, 806 m mCC, dCH3, phenyl; 727 m paraffin;
718 m, 706 m, 640 w, 596 w,560 w, 532 w, 459 m, 445 m mGaC.
Characterization of the [3,3,3]-cyclophane 2a (R = Et). Yield:
Characterization of the addition product 4b (R = nPr). Yield:
5% of pure 4b; owing to its very high solubility in hydrocarbon
solvents the recrystallization of 4b from n-pentane gave very low
yields only. Mp (argon, sealed capillary): 130 ◦C. 1H NMR (C6D6,
44%. Decomp. (argon, sealed capillary): above 220 ◦C. 1H NMR
=
(C6D6, 400 MHz): d = 6.26 (6 H, s, C C–H), 6.24 (6 H, s, C6H3),
3
1.36 (9 H, t, JHH = 8 Hz, Me of ethyl), 1.13 (54 H, s, CMe3),
0.97 (6 H, q, JHH = 8 Hz, CH2 of ethyl). 13C NMR (C6D6,
3
=
400 MHz): d = 6.58 (4 H, s, C6H3), 6.19 (2 H, s, C C–H), 1.58
(8 H, pseudo-sextet, 3JHH = 7.4 Hz, CH2CH2CH3), 1.05 (18 H, s,
=
=
100 MHz): d = 155.3 (Ga–C C-H), 153.9 (Ga–C C–H), 144.7
3
(ipso-C of phenyl), 121.5 (ortho-C of phenyl), 36.7 (CMe3), 31.8
=
C C–CMe3), 1.03 (12 H, t, JHH = 7.4 Hz, Me of propyl), 0.66
(br., 8 H, t, 3JHH = 7.4 Hz, GaCH2). 13C NMR (C6D6, 100 MHz):
(CMe3), 10.5 (Me of ethyl), 4.8 (br., CH2 of ethyl). IR (CsBr plates,
−1
=
paraffin, cm ): 1582 s, 1558 vs mC C, phenyl; 1455 vs, 1377 vs
=
=
d = 155.6 (Ga–C C–H), 154.3 (Ga–C C–H), 142.2 (ipso-C of
paraffin; 1306 m dCH3; 1225 m, 1202 m, 1170 w, 1155 w, 1138 sh,
1088 vw, 1058 vw, 1038 w, 1028 w, 989 m, 937m, 912 m, 897 m
mCC, dCH3, phenyl; 721 s paraffin; 706 m, 660 w, 600 w, 573 w,
560 vw, 523 w, 453 w mGaC.
phenyl), 126.6 (ortho-C of phenyl), 37.1 (CMe3), 31.6 (CMe3), 20.8
(Ga–CH2), 20.0 (Me of propyl), 19.8 (CH2CH2CH3). IR (CsBr
−1
=
plates, paraffin, cm ): 1654 m, 1599 s, 1571 s, 1497 s mC C, phenyl;
1454 vs paraffin; 1408 s dCH3; 1360 s paraffin; 1325 m, 1298 w,
1258 m dCH3; 1229 m, 1202 s, 1187 m, 1155 m, 1101 m, 1059 s,
1020 m, 986 m, 939 w, 905 w, 864 w, 808 w, 785 w mCC, dCH3,
phenyl; 731 m paraffin; 689 br., sh, 673 s, 654 br., s, 554 br., m,
457 w mGaC. MS (EI, 70 eV): m/z (%) (three most intensive peaks
only, complete isotopic patterns as expected) = 551, 552, 553 (16,
6, 11; M+); 396, 397, 398 (1, 0.7, 0.8; M+ − Ga − isopropyl −
propene); 353, 354, 355 (100, 23, 68; M+ − GaiPr2 − propene).
Characterization of the [3,3,3]-cyclophane 2b (R = nPr). Yield:
57%. Decomp. (argon, sealed capillary): above 210 ◦C. 1H NMR
=
(C6D6, 400 MHz): d = 6.31 (6 H, s, C6H3), 6.25 (6 H, s, C C–H),
3
1.83 (6 H, pseudo-sextet, JHH = 7.6 Hz, CH2CH2CH3), 1.14 (9
3
H, t, JHH = 7.6 Hz, Me of propyl), 1.13 (54 H, s, CMe3), 1.05
(6 H, pseudo-triplet, JHH = 7.6 Hz, GaCH2). 13C NMR (C6D6,
3
=
=
100 MHz): d = 155.6 (Ga–C C–H), 154.7 (Ga–C C–H), 145.1
(ipso-C of phenyl), 121.1 (ortho-C of phenyl), 36.8 (CMe3), 31.9
Crystal structure determinations of 2a, 2b and 4b
(CMe3), 20.5 (CH2CH2CH3), 20.0 (Me of propyl), 15.9 (Ga–CH2).
−1
=
IR (CsBr plates, paraffin, cm ): 1582 s, 1564 s mC C, phenyl;
Single crystals of compound 2a were obtained from a saturated
solution in n-hexane upon cooling to −15 ◦C, crystals of 2b by slow
concentration of a solution in cyclopentane at room temperature,
those of 4b from n-pentane at −45 ◦C. The crystallographic data
were collected with a Bruker Smart Apex diffractometer. The
structures were solved by direct methods and refined with the
program SHELXL-9715 by a full-matrix least-squares method
basedon F2. Crystal data, data collection parameters and structure
refinement details are given in Table 1. Compound 2a crystallizes
with half an n-hexane molecule per formula unit. The crystals of
2b enclose cyclopentane molecules, one of which is strongly disor-
1455 vs, 1377 vs paraffin; 1325 w, 1310 w, 1287 vw, 1272 vw dCH3;
1226 s, 1202 s, 1165 w, 1150 w, 1135 w, 1059 m, 1037 w, 1025 w,
989 m, 939 w, 913 m, 898 w, 883 w mCC, dCH3, phenyl; 724 m
paraffin; 706 s, 647 w, 534 w, 458 w mGaC. MS (EI, 70 eV): m/z
(%) (three most intensive peaks only, complete isotopic patterns
as expected) = 979, 981, 983 (0.4, 0.7, 0.6; M+ + H), 935, 937, 939
(3.7, 8.1, 6.5; M+ − Pr).
Characterization of the [3,3,3]-cyclophane 2c (R = iPr). Yield:
61%. Decomp. (argon, sealed capillary): above 210 ◦C. 1H NMR
=
(C6D6, 400 MHz): d = 6.35 (6 H, s, C6H3), 6.21 (6 H, s, C C–H),
1.64 (3 H, septet, 3JHH = 7.6 Hz, CHMe2), 1.44 (18 H, d, 3JHH
=
dered over a crystallographic 3 axis. The cyclophane molecules of
¯
7.6 Hz, Me of isopropyl), 1.12 (54 H, s, CMe3). 13C NMR (C6D6,
compound 2b are located on crystallographic threefold rotation
=
=
100 MHz): d = 155.0 (Ga–C C–H), 153.7 (Ga–C C–H), 145.0
axes.
422 | Dalton Trans., 2007, 417–423
This journal is
The Royal Society of Chemistry 2007
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