Martin B. Smith
Apr 1, 1970
Citations
0
Influential Citations
40
Citations
Journal
Journal of Organometallic Chemistry
Abstract
Abstract The monomer-dimer equilibrium of liquid triisobutylaluminum (TiBA) has been studied by a thermochemical method applied earlier to triethylaluminum (TEA). The values obtained for the heat and entropy of dissociation of 1 mole of TiBA dimer are 8.1 6 ±0.1 2 kcal and 30.4 9 ±0.3 4 cal/deg. These values, compared with corresponding values for triethylaluminum (16.9 kcal and 32.2 cal/deg), indicate that a large steric effect is involved in the formation of the dimeric molecule. This suggests an appreciable increase in the (average) lengths of the Al CH 2 and Al Al bonds in the bridge accompanied by a significant increase in rotational restriction. Degrees of dissociation of TiBA in the pure liquid state and at various mole fractions in hydrocarbon solution are tabulated over a wide temperature range. The results, which are consistent with literature data, indicate that TiBA is 39.4% associated at 10° and 16.4% associated at 40°. This contradicts the widely held belief that (pure) TiBA is either “completely monomeric” or practically unassociated.