RESUMEN
Addition of tert-butylisocyanide or 2,6-dimethylphenylisocyanide to a solution of trialkylaluminum or trialkylgallium results in formation of complexes R(3)M·C≡N(t)Bu (M = Al, R = Me (1), Et (2), (i)Bu (3), (t)Bu (4); M = Ga, R = (t)Bu (9)) or R(3)M·C≡N(2,6-Me(2)C(6)H(3)) (M = Al, R = Me (5), Et (6), (i)Bu (7), (t)Bu (8); M = Ga, R = (t)Bu (10)), respectively. Complexes 1, 4, 5, and 8-10 are isolated as solids, whereas the triethylaluminum and triisobutylaluminum adducts 2, 3, 6, and 7 are viscous oils. Complexes 1-10 were characterized by NMR ((1)H, (13)C) and IR spectroscopies, and the molecular structures of 4, 5, and 8-10 were also determined by X-ray crystallography. The frequency of the C≡N stretch of the isocyanide increased by 58-91 cm(-1) upon complexation, consistent with coordination of the isocyanide as a σ donor. Enthalpies of complex formation for 1-10 were determined by isothermal titration calorimetry. Enthalpy data suggest the following order of decreasing Lewis acidity: (t)Bu(3)Al â« (i)Bu(3)Al ≥ Me(3)Al ≈ Et(3)Al â« (t)Bu(3)Ga. In the absence of oxygen and protic reagents, the reported complexes do not undergo insertion or elimination reactions upon heating their benzene-d(6) solutions to 80 °C.
RESUMEN
The title compound, [Al(CH3)2(C13H17N2)] (systematic name; {2-[(di-ethyl-amino)-meth-yl]indol-1-yl-κ(2) N,N'}di-methyl-aluminium), was prepared by methane elimination from the reaction of 2-(di-ethyl-amino-meth-yl)indole and tri-methyl-aluminium. The complex crystallizes readily from a concentrated toluene solution in high yield. The asymmetric unit contains two crystallographically independent mol-ecules. Each mol-ecule has a four-coordinate aluminium atom that has pseudo-tetra-hedral geometry. C-Hâ¯π inter-actions link the independent mol-ecules into chains extending along the b-axis direction.