Alkoxohydridoaluminates. Part 2. The influence of alkyl substituents, solvent, and temperature on the molar fractions of components, equilibrium constants, and 27Al n.m.r. data for equilibrium mixtures containing Bu4N+AlH4-n(OR)n–

Abstract

Molar fractions, equilibrium constants of mutual exchange, and ²⁷Al n.m.r. data of compounds Bu₄N⁺AlH_4-n(OR)^–_n and the dependence of these on n(0–4); R (Me, Et, Nonyl, Prⁱ, cyclo-C₆H₁₁ Ph, and Bu^t); solvent (benzene, tetrahydrofuran, 1,2-dimethoxyethane, diglyme); and temperature (23 and 70 °C) are presented. Predominant separation of cation from anion and, consequently, the slowest exchange, is found with Bu₄N⁺AlH(OR)^–₃ and bulky R, in 1,2-dimethoxyethane at 70 °C. Such compounds, free of tetra-, tri- and di-hydrido components are expected to exhibit a very high reduction stereoselectivity proportional to the steric strain resulting from the presence of all three bulky alkoxy groups.