Ethene polymerization at cationic aluminum amidinate and neutral aluminum alkyl. A theoretical study

The effect of substituent variation on olefin insertion and chain, transfer in cationic aluminum amidinate alkyls [(RC)-C-1(NR2)(2)AlEt](+) was studied by theoretical methods. Introduction of bulky substituents at C (t-Bu) and N (i-Pr) favors insertion more than chain transfer, but the system still keeps a clear preference for chain transfer, and even the full system [t-BuC(Ni-Pr)(2)AlEt](+) is predicted not to polymerize ethene. Changing to-a neutral analogue (as in H2C(NH)(2)AlEt) and relieving the geometric constraints (in Me2AlEt) favor insertion even more, so that trialkylaluminum is finally predicted to have a clear preference for oligomerization