One-pot solvothermal synthesis of a well-ordered layered sodium aluminoalcoholate complex: a useful precursor for the preparation of porous Al₂O₃ particles

Abstract

One-pot solvothermal synthesis of a robust tetranuclear sodium hexakis(glycolato)tris(methanolato)aluminate complex Na3[Al4(OCH3)3(OCH2CH2O)6] via a modified yet rigorous base-catalyzed transesterification mechanism is presented here. Single crystal X-ray diffraction (SCXRD) studies indicate that this unique Al complex contains three penta-coordinate Al3+ ions, each bound to two bidentate ethylene glycolate chelators and one monodentate methanolate ligand. The remaining fourth Al3+ ion is octahedrally coordinated to one oxygen atom from each of the six surrounding glycolate chelators, effectively stitching the three penta-coordinate Al moieties together into a novel tetranuclear Al complex. This aluminate complex is periodically self-assembled into well-ordered layers normal to the [110] axis with the intra-/inter-layer bindings involving extensive ionic bonds from the three charge-counterbalancing Na+ cations rather than the more typical hydrogen bonding interactions as a result of the fewer free hydroxyl groups present in its structure. It can also serve as a valuable precursor toward the facile synthesis of high-surface-area alumina powders using a very efficient rapid pyrolysis technique.

Designed Single‐Step Synthesis, Structure, and Derivative Textural Properties of Well‐Ordered Layered Penta‐coordinate Silicon Alcoholate Complexes

“…[2, 3a, 4] The 13 C{ 1 H} MAS NMR spectrum (Figure 3 B) shows two well-resolved regions which can be assigned to the ethylene glycolate (63 ppm) and methanolate (53 ppm) ligands. [24] The carbon ratio between the glycolate and methanolate sites using both direct excitation and cross polarization (CP) gives about 4:1, corroborating the monomeric BU structure determined by SCXRD studies. Since the carbon atoms (C5 and C6) of one of the four glycolates are position-disordered, we speculate the disorder of the glycolates is the cause of the extra shoulder resonances observed in the 13 C MAS NMR spectrum (i.e., 66 and 54 ppm in Figure 3 B).…”

“…[2,3a,4] The 13 C{ 1 H} MAS NMR spectrum (Figure 3 B) shows two well-resolved regions which can be assigned to the ethylene glycolate (63 ppm) and methanolate (53 ppm) ligands. [24] The carbon ratio between the glycolate and methanolate sites using both direct excitation and cross polarization (CP) gives ca . 4:1, corroborating the monomeric BU structure determined by SCXRD studies.…”

“…gions are also observed in the 13 C{ 1 H} MAS NMR spectrum of the B-undoped Si complex Na 2 Si 2 (OCH 2 CH 2 O) 5 (Figure 3 C) with the least intense resonance at 52.5 ppm probably attributable to a very small number of the unbound MeOH solvent molecules tightly occluded in the interplanar voids, as found in ref. [24]. There remain three resolvable resonances in the bound glycolate domain with an intensity ratio of about 1:2:2.…”

Stereoisomerism in Tetrametallic Propeller‐Like Complexes: A Solid‐State and Solution NMR Study on a Tetragallium(III) Derivative

“…The coordination environment of the gallium(III) ions lying on the twofold axis (Ga1 and Ga2) is ordered within experimental resolution, except for a rotationally disorder tBu group in the two symmetry-related dpm À ligands (dpm1) bound to Ga2 [0.614(7):0.386 (7)]. By contrast, the two dpm À ligands coordinated to Ga3 (dpm2 and dpm3) exhibit both propeller-like (p) and sandwich-like (s) coordination modes, with 0.8393(18) and 0.1607(18) occupancies, respectively, but unresolved splitting of O atoms.…”

“…Tetrametallic complexes with a chiral, propeller-like structure similar to that of Werner's "hexol" salts [1][2][3] and of some Group 13 alkoxides and aryloxides [4][5][6][7][8][9][10][11][12][13][14][15][16][17] are of great historical significance in coordination chemistry. When the metal ions carry a spin (s), this metal-centred triangular topology is magnetically appealing, as the ground state has nonzero total spin (S) for both ferro-and antiferromagnetic interactions between the central (M c ) and peripheral (M p ) metal centres.…”