Alkylaluminum complexes containing pyridyl amido ligands. Syntheses and characterization of AlMe2[N(CH2-2-Py)2], Al2Me5[N(CH2-2-Py)2], and Al2Me4[2,3,5,6-tetra(2-pyridyl)piperazyl], an unusual carbon–carbon bond coupling product

Abstract

The reactions of AlMe3 with di(2-pyridylmethyl)amine have been investigated. Two new complexes, AlMe2[N(CH2-2-Py)2] (1) and Al2Me4[2,3,5,6-tetra(2-pyridyl)piperazyl] (3), were obtained as the major and the minor product, respectively, from the reaction of AlMe3 with di(2-pyridylmethyl)amine in a 1:1 ratio in toluene at 23 °C. The reaction of AlMe3 with di(2-pyridylmethyl)amine in a 2:1 ratio yielded a dinuclear complex Al2Me5[N(CH2-2-Py)2] (2). These complexes were fully characterized by NMR, and elemental and single-crystal X-ray diffraction analyses. Crystal data: 1, C14H18N3Al, monoclinic, P21/m, a = 7.568(2), b = 7.340(1), c = 13.120(8) Å, β = 104.17(3)°, V = 706.6(4) Å3, Z = 2; 2, C14H27N3Al2, triclinic, [Formula: see text], a = 8.422(1), b = 16.711(6), c = 7.659(1) Å, α = 91.94(2)°, β = 113.08(1)°, γ = 85.17(2)°, V = 988.2(4) Å3, Z = 2; 3, C28H32N6Al2, monoclinic, P21/c, a = 7.522(8), b = 15.841(8), c = 11.584(4) Å, β = 98.53(5)°, V = 1365(1) Å3, Z = 2. Compound 1 is a mononuclear complex with the aluminum atom in an approximately trigonal bipyramidal geometry and the amido nitrogen atom in a trigonal planar geometry. Compound 2 contains two aluminum centers bridged by an amido nitrogen atom where one of the aluminum atoms has a tetrahedral geometry while the other has a trigonal bipyramidal geometry. The dinuclear compound 3 can be described as the result of two unusual C—C bonds coupling between the methylene carbon atoms of two molecules of 1. The aluminum coordination environment in 3 is similar to that of 1. Key words: aluminum, amide, pyridyl, 2,3,5,6-tetra(2-pyridyl)piperazine, structure.