EFFECTS OF RING SUBSTITUENTS, PREFERENTIAL SOLVATION, AND ADDED AMINE ON THE TRIMER-DIMER EQUILIBRIUM IN CYCLIC DIALKYLALUMINUM AMIDE COMPOUNDS

Multinuclear NMR studies of the dialkylaluminum amides [R2A1NR′2]X(R = CH3, C2H5, i-C4H9, i-C4H9; R′2= H2, (CH3)2, (CH2)2) were carried out as a function of temperature and concentration in aromatic hydrocarbon solvents and in the presence of added RNH2(R = H, CH3). Equilibrium constants, ΔH, and ΔS for the trimer—dimer (x = 3, 2) equilibria in solution were obtained. The results were interpreted in terms of steric interactions, ring strain, and preferential solvation. In addition to qualitative increases in the rates of trimer-dimer equilibration, rapid amine exchange was observed in the presence of added RNH2. The effects of added amine were attributed to amine-catalyzed ring-opening reactions. The potential relevance of these observations to aluminum nitride synthesis via pyrolysis of such dialkylaluminum amides was noted. © 1990, American Chemical Society. All rights reserved.