Gas-Phase Lewis Acidity of Perfluoroaryl Derivatives of Group 13 Elements

The gas-phase Lewis acidity of group 13 element aryl and perfluorinated aryl derivatives E(C 6 H 5 ) 3, E(C 6 H 4 F) 3, and E(C 5 F 5 ) 3 (E = B, Al, Ga) toward different donor molecules (NH 3, H 2 O, PH 3, H −, CH 3 −, F − ) has been theoretically studied at the RI-BP86/def2-TZVPP level of theory. The following order of the acceptor ability has been established: E(C 6 H 5 ) 3 ≈ E(C 6 H 4 F) 3 < E(C 6 F 5 ) 3 ≈ ECl 3 . The acceptor strengths of E(C 6 H 5 ) 3 and E(C 6 H 4 F) 3 are comparable to each other but much weaker compared to E(C 6 F 5 ) 3, which has a similar acceptor strength to those of the corresponding trihalides ECl 3 . The acceptor ability of ER 3 decreases in the order Al > Ga > B. In the gas phase, Al(C 6 F 5 ) 3 is found to be a stronger Lewis acid than B(C 6 F 5 ) 3 toward all electron donors but H − . In contrast to AlCl 3, which forms stable dimers, Al(C 6 F 3 ) 3 is monomeric and therefore has a much higher Lewis acid reactivity . The reactivity of perfluorinated derivatives E(C 5 F 5 ) 3 (E = B, Al, Ga) toward ammonolysis and hydrolysis processes and L 2 ZrMe 2 (L = Cl, Cp, Cp*) as cocatalysts in olefin polymerization is also discussed.