MIXED-DONOR AND MONOMERIC N-DONOR ADDUCTS OF ALANE

Reaction of H3Al.NMe3 With 1,2-bis(dimethylphosphino)ethane (=dmpe) affords the novel mixed-donor aluminum hydride complex 2(Me3N.AlH3).dmpe (1) with the N- and P-donor groups in apical trigonal bipyramidal positions (structurally authenticated) which has been modeled by ab initio calculations on H3N.AlH3.PMe3 and H3Al.PMe3. The complexes [H3Al.MeMorph]infinity (2) (MeMorph = N-methylmorpholine) and H3Al-quin (3) (quin = quinuclidine) are prepared from LiAlH4 and hydrochloride salts of the appropriate amines. Complex 2 is polymeric in the solid state, displaying donation from the N- and O-centers of successive ligands, unlike 3, which is a monomer with four-coordinate metal centers and displays no reactivity toward dmpe. Crystal data (Mo Kalpha, lambda = 0.710 69 angstrom): 1, monoclinic, space group P2(1)/n, a = 6.694(2) angstrom, b = 24.775(6) angstrom, c = 7.044(2) angstrom, V = 1168(6) angstrom3, Z = 2, R = 0.097; 2, orthorhombic, space group P2(1)2(1)2(1), a = 13.504(4) angstrom, b = 9.799(3) angstrom, c = 5.965(2) angstrom, V = 789 angstrom3, Z = 4, R = 0.093; 3, monoclinic, space group P2(1)/m, a = 6.138(1) angstrom, b = 9.066(2) angstrom, c = 8.213(2) angstrom, V = 453.0(2) angstrom3, Z = 2, R = 0.056.