title: N-methylacridinium salts: carbon Lewis acids in frustrated Lewis pairs for σ-bond activation and catalytic reductions.
abstract: N-methylacridinium salts are Lewis acids with high hydride ion affinity but low oxophilicity. The cation forms a Lewis adduct with 4-(N,N-dimethylamino)pyridine but a frustrated Lewis pair (FLP) with the weaker base 2,6-lutidine which activates H2, even in the presence of H2O. Anion effects dominate reactivity, with both solubility and rate of H2 cleavage showing marked anion dependency. With the optimal anion, a N-methylacridinium salt catalyzes the reductive transfer hydrogenation and hydrosilylation of aldimines through amine-boranes and silanes, respectively. Furthermore, the same salt is active for the catalytic dehydrosilylation of alcohols (primary, secondary, tertiary, and ArOH) by silanes with no observable over-reduction to the alkanes.
authors.affiliation: School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL (UK).
authors.forename: Ewan R
authors.initials: ER
authors.lastname: Clark
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Ingleson
keywords: Lewis acids; frustrated Lewis pairs; reduction; silanes; synthetic methods