Synthesis and Structure of Metal-Containing Eight- and Twelve-Membered M–N–C–O–Heterocycles (M=Al,Ga,In)

The novel compounds [Cl₃CC(O)N(H)AlMe₂]₂, 1, [Cl₃CC(O)N(H)GaMe₂]₂ 2, [Cl₃CC(O)N(H)InMe₂]₂ 3, and [2,4,6-(CF₃)₃C₆H₂C(O)N(H)A1Me₂]₃ 4, were prepared in good to high yields by the reaction of Me₃Al, Me₃Ga and Me₃In with 2,2,2-trichloroacetamide and of Me₃Al with 2,4,6-tris(trifluoromethyl) benzamide, respectively. 1–4 are fully characterised by elemental analysis, IR, NMR and mass spectroscopy. The crystal structures of 1,2 and 4 have been determined. 1 crystallises in the space group C2/c, a = 1802.9(3), b = 628.9(1), c = 1781.4(3) pm, β = 113.94(1)°,V = 1.8461(5) nm³, ρ_calcd= 1.572 Mgm⁻¹, Z = 4 and 3278 observed reflections, R = 0.038 (I > 2σ(I)), wR2 = 0.097 (all data), 2 in the space group P2₁/n, a = 871.3(2), b = 885.7(3), c = 1243.5(3) pm, β = 105.84(2)°, V = 0.9232(4) nm³, ρ_calcd= 1.879 Mgm⁻¹, Z = 2 and 4296 observed reflections, R = 0.024 (I > 2σ(I)), wR2 = 0.057 (all data), and 4 in the space group C2/c, a = 3141.4(6), b = 1800.0(8), c = 1751.3(7) pm, β = 105.49(6)° V, = 9.543(8) nm³, ρ_calcd = 1.592 Mgm⁻¹, Z = 8 and 9148 observed reflections, R = 0.073(1 > 2σ(I)), wR2 = 0.188 (all data). The structures of 1 and 2 display eight-membered ring systems in a boat and chair conformation, respectively, whereas the core of 4 is a twelve-membered heterocycle.