91.
Reaction of the optically active primary amine (S)-(—)--methylbenzylamine with trimethylaluminium in heptane affords the crystalline organoaluminium dimer (S)-(—)-(S)-(—)-[(C
6H
5)CH(CH
3)NHA1(CH
3)
2]
2. Isolated as large, colourless, extremely air-sensitive prismatic crystals, the title compound crystallizes in the orthorhombic space group
P2
12
12
1 with unit cell parameters
a = 8.406(3),
b = 15.505(4),
c = 17.547(5) Å,
V = 2287 Å
3 and p = 1.03 g cm
−3 for
Z = 4. Least-squares refinement based on 1477 observed reflections converged at
R = 0.056, R
w = 0.058. Methane was eliminated during the course of the reaction due to cleavage of A1---C and N---H bonds resulting in an asymmetric A1
2N
2 fragment at the core of the organoaluminium dimer. The mean A1---C bond distance in the dimethylaluminium units is 1.930(8), while the mean A1---N bond distance is 1.950(5) Å. Specific rotation ([]
D25 in CH
2C1
2)of the dimer is determined to be - 20.6°.
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