Catalyst activation and the dimerization energy of alkylaluminium compounds

Alkyl/halide bridged aluminium systems, relevant to e.g. olefin polymerization are known problem cases for DFT. 'Chemical accuracy' can be reached with the M06-2X functional or TPSSTPSS-D2. Alkylation of olefin polymerization catalyst precursors is exergonic for most electronegative groups X (F, Cl, OR, NR2) provided the Me2AlX-dimerization energies are taken into account.