Oxygen-17 and aluminium-27 nuclear magnetic resonance spectroscopic investigations of aluminium(III) hydrolysis products

Abstract

We report the ¹⁷O and ²⁷Al nuclear magnetic resonance (n.m.r.) spectra of the products of aluminium(III) hydrolysis by base. Our results indicate that combined use of solution (chemical shift, linewidth, and spin-lattice relaxation time) and solid-state (static, ‘magic-angle’ sample spinning, and cross-polarization ‘magic-angle’ sample spinning) n.m.r. techniques permits determination of nuclear quadrupolar coupling constants (e²qQ/h, in solution and solid state) for both ¹⁷O and ²⁷Al nuclei, and in suitable cases, measurement of rotational correlation times in solution. Cross polarization allows differentiation between AlO₄ and Al–O–H oxygens in solid-state n.m.r. spectra of tridecamer crystals. The ¹⁷O e²qQ/h value for AlO₄ is in good agreement with predictions based on electronegativity considerations. The AlO₄ oxygens in the tridecamer are essentially inert to substitution, while the others are quite labile. The rotational correlation time of the tridecamer in solution at 23 °C is ca. 1.3 × 10^–10 s.