STRUCTURAL STUDIES ON MESITYLALUMINUM ADDITION-COMPOUNDS

Four mesitylaluminum derivatives, Mes(3)Al.(4-picoline)(C7H8)(0.5) (1) , EtMes(2)Al.THF (2), Mes(2)-ClAl.THF (3), and [Mes(2)Al(mu-Cl)](2) (4 ) (Mes = 2,4,6-trimethylphenyl), have been prepared and their structur es determined by single crystal X-ray diffraction methods. Compound 1 crystallizes in the monoclinic space group C2/c (No. 15): a = 43.784(1 5) Angstrom, b = 8.901(1) Angstrom, c = 16.760(2) Angstrom, beta = 104 .02(2)degrees, Z = 8, R = 10, and R(w) = 9.9. Compound 2 crystallizes in the orthorhombic space group P2(1)2(1)2(1) (No. 19): a = 12.057(9) Angstrom, b = 13.490(3) Angstrom, c = 14.037-(2) Angstrom, Z = 4, R = 5.4, and R(w) = 3.9. The halide derivative 3 crystallizes in the primi tive monoclinic space group P2(1)/a (No. 14): a = 17.18(1) , b = 14.75 4(2) Angstrom, c = 17.316(2) Angstrom, beta = 92.74(3)degrees, Z = 8, R = 6.5, and R(w) = 2.4. The base-free compound 4 exists as a dimer an d crystallizes in the space group P2(1)/c (No. 14): a 12.288(2) Angstr om, b = 15.824(3) Angstrom, c = 9.905(2) Angstrom, beta = 108.43(2)deg rees, Z = 4, R = 5.4, and R(w) = 5.9. The distortion associated with 1 , 2, and 3 relative to the parent monomeric molecule, Mes(3)Al, is dis cussed with respect to substitution of the mesityl group for the Cl an d Et ligands.