PROTON MAGNETIC RESONANCE STUDIES OF MIXED ALUMINUM ALKYLS .I. ALUMINUM TRIALKYLS

The systems AlMe3-AlEt3, AlMe3-Al(n-Pr)s, and AlMe3-Al(i-Bu)3 were studied by means of pmr spectroscopy at room temperature as well as at low temperature. A bridge-bonding factor, defined as a measure of the tendency of an alkyl group to occupy the bridge position in the mixed dimer formed in the aluminum trialkyl mixture, was experimentally determined for ethyl, n-propyl, and isobutyl groups in the trialkylaluminum dimers as compared with methyl group and was found to be 1/6, 1/7, and 1/17n, respectively. It depends upon the bulkiness of the alkyl group. In terms of the bridge-bonding factor, the chemical shifts of the α-methyl and the α-methylene groups of the mixed dimers in the mixtures were calculated and compared with the experimental values. The equilibrium between the various dimers in each system was also discussed.