POLYDENTATE LIGAND CHEMISTRY OF GROUP 13 METALS - EFFECTS OF THE SIZE AND DONOR SELECTIVITY OF METAL-IONS ON THE STRUCTURES AND PROPERTIES OF ALUMINUM, GALLIUM, AND INDIUM COMPLEXES WITH POTENTIALLY HEPTADENTATE (N4O3) AMINE PHENOL LIGANDS

The aluminum, gallium and indium complexes of potentially heptadentate (N4O3) tripodal amine phenol ligands (H3L1 = tris(2'-hydroxybenzylaminoethyl)amine, H3L2 = tris(5'-chloro-2'-hydroxybenzylaminoethyl)amine, and H3L3 = tris(5'-bromo-2'-hydroxybenzylaminoethyl)amine) have been prepared and characterized. The spectral (IR, FAB-MS, and H-1 NMR) properties of these complexes are reported. The reaction of Al3+ or Ga3+ with N4O3 amine phenols in presence of 3 equiv of a base (acetate or hydroxide) afforded cationic complexes, [M(HL)]X (M = Al, L = L1, L2, L3, X = ClO4-; M = Ga, L = L1, L3, X = NO3-, Cl-), while neutral In complexes [ln(L)] (L = L1, L2, L3) were obtained from similar reactions. The molecular structures of [Al(HL2)]ClO4.2CH3OH, [Ga(HL3)]Cl.CHCl3, and Na[In(L1)](NO3)(H2O)(C2H5OH).2.65H2O were determined by X-ray methods. Crystals of [AI(HL2)](ClO4).2CH3OH are triclinic, P1, a = 9.2567 (9) angstrom, b = 11.6025 (9) angstrom, c = 8.9471 (6) angstrom, alpha = 109.251 (6)-degrees, beta = 96.952 (8)-degrees, gamma = 71.452 (7)-degrees, V = 859.9 (1) angstrom3, and Z = 1; those of [Ga(HL3)]CI.CHCl3 are monoclinic, P2(1)/n, a = 11.390 (3) angstrom, b = 14.306 (2) angstrom, c = 21.700 (2) angstrom, beta = 92.29 (1)-degrees, V = 3533 (1) angstrom3, and Z - 4; and those of Na[In(Ll)](NO3)(H2O)(C2H5OH).2.65H2O are tetragonal, I4(1)/a, a = 18.974 (2) angstrom, c - 39.255 (3) angstrom, V = 14133 (2) angstrom3, and Z = 16. The three structures were refined to R = 0.037, 0.052, and 0.043 and R(w) = 0.045, 0.061, and 0.053 for 3471, 4979, and 4903 observed reflections with I greater-than-or-equal-to 3sigma(I), for the Al, Ga, and In complexes, respectively. The Al atom in [Al(HL2)]ClO4.2CH3OH is coordinated by an N3O3 donor set from the N4O3 amine phenol ligand in a distorted octahedral coordination geometry with one (N(4)) of the three secondary amine N atoms being protonated and uncoordinated. The Ga atom in [Ga(HL3)]CI-CHCl3 is bonded by six (N4O2) donor atoms of the N4O3 amine phenol ligand in a distorted octahedral geometry with one phenol oxygen being protonated and uncoordinated. In Na[In(L1)](NO3)(H2O)(C2H5OH).2.65H2O, all seven (N4O3) donors coordinate to the In atom in a monocapped distorted octahedral arrangement. The structural differences among these complexes are in terms of the donor atom selectivity and the size of the metal ions. Variable-temperature H-1 NMR spectral data revealed rigid solution structures for both the aluminum and gallium complexes. These complexes remained very rigid at solution temperatures higher than 120-degrees-C. Stereochemical changes in the indium complexes were observed at room temperature, and they undergo an intramolecular dissociative inversion at the coordinated N atoms at elevated temperatures. The H-1 NMR spectral properties of aluminum, gallium, and indium complexes are discussed in relation to their structural differences.