SYNTHESES AND CRYSTAL-STRUCTURES OF POLYNUCLEAR ORGANOALUMINUM-MAGNESIUM COMPLEXES AND THEIR OXIDATIVE PRODUCTS

This paper reports the syntheses of a number of aluminum-magnesium complexes. Reaction of {[(Me(3)Si)(2)N]Mg-2)(2)(1,4-dioxane) (1) with trimethylaluminum produces [{(R(2)N)Mg(Me)}(2){Mg(NR(2))(NR(2)AlMe(3))}(2)] (R=SiMe(3)) (2) and {Me(2)Al[N(SiMe(3))(2)]}(2)(1,4-dioxane) (3). Compound 2 is a dialuminum-tetramagnesium complex with unusual linear metal methyl-metal bridge groups. Reactions of Mg[N(i-Pr)(2)](2) with AlEt(3) and Mg[N(i-Bu)(2)](2) with AlMe(3) also afford Al-Mg complexes. However, reaction of Mg(NMe(2))(2) and Mg[N(n-Pr)(2)](2) with AlMe(3) and reaction of Mg(NEt(2))(2) with Al(i-Bu)(3) produce dialuminum complexes. In order to understand why Al dimers formed rather than Al-Mg complexes, {Me(2)Al(mu-NEt(2))(2)Mg(mu-Me)}(2) (A) was heated to produce the dialuminum complex [Me(2)Al(mu-NEt(2))](2). Insertion of O-2 into the Mg-R bond of Al-Mg complexes resulted in the formation of the magnesium alkoxide derivatives {R(2)Al(mu-NR'(2))(2)Mg(mu-OR)}(2) (13, R=Me, R'=i-Pr; 14, R=Et, R'=Et; 15, R=Me, R' =Et; 16, R=Me, R'=i-Bu). The molecular structures of compounds 2, 3, and 13 were determined by X-ray diffraction. Compound 2 crystallizes in the triclinic space group Pi with unit cell parameters a=12.288(5)Angstrom, b=12.698(6)Angstrom, c=14.285(7)Angstrom, alpha=101.79(4)degrees, beta=90.07(3)degrees, gamma=111.57(3)degrees, V=2022(2)Angstrom(3), and Z= 1, compound 3 crystallizes in the monoclinic space group P2(1)/c with unit cell parameters alpha=14.804(5)Angstrom, b= 7.475(3)Angstrom, c=15.378(5)Angstrom,beta=100.77(3)degrees, V=1672(1)Angstrom(3), and Z=2, and compound 13 crystallizes in the monoclinic space group P2(1)/n with unit cell parameters alpha=8.893(1)Angstrom, b=13.995(2)Angstrom, c=16.382(3)Angstrom,beta=96.60(1)degrees, V=2025.6(6)Angstrom(3), and Z=2.