Imidazolium formation from the reaction of N-heterocyclic carbene stabilised group 13 trihydride complexes with organic acids

Abstract

Stoichiometric reaction of NHC stabilised aluminium trihydride species with 3.0 equivalents of phenol generates imidazolium tetraphenoxyaluminate species. Reaction of [InH3(IMes)] (IMes = CN(2,4,6-Me3C 6H2)C2H2N(2,4,6-Me3C 6H2)) with 1.0 equivalent of 1,1,1,5,5,5-hexafluoropentan- 2,4-dione renders [IMes • H][CH{C(O)CF3}2]with immediate indium trihydride decomposition. The molecular structures of two imidazolium species are discussed. The reactions of the N-heterocyclic carbene (NHC) stabilised group 13 trihydride complexes [AlH3(IMeMe)] (1) (IMeMe = 1,3,4,5-tetramethylimidazol-2-ylidene), [AlH3(I iPrMe)] (2) (IiPrMe = 1,3-diisopropyl-4,5- dimethylimidazol-2-ylidene) with three molar equivalents of phenol, and [InH3(IMes)] (3) (IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazole-2- ylidene) with one molar equivalent of 1,1,1,5,5,5-hexafluoropentan-2,4-dione (F6acacH) are presented. These render the imidazolium tetraphenoxyaluminate species; [IMeMe • H][Al(OPh)4] (4) and [IiPrMe • H][Al(OPh)4] (5), and 1,3-bis(2,4,6- trimethylphenyl)imidazolium 1,1,1,5,5,5-hexafluoropentan-2,4-dionate; [IMes • H][CH{C(O)CF3}2] (6), the latter leading to metallohydride decomposition. The molecular structures of 4 and 6 are described. © 2004 Elsevier B.V. All rights reserved.