Stoichiometric Reactions and Catalytic Hydrogenation with a Reactive Intramolecular Zr+/Amine Frustrated Lewis Pair

Methyl anion abstraction from Cp*2Zr­(CH3)­OCH2CH2NiPr2 (13) with trityl cation generates [Cp*2Zr­(OCH2CH2NiPr2)]+ (14). Complex 14 behaves as a reactive Zr+/amine frustrated Lewis pair (FLP). It reacts with dichloromethane to give the [Zr]­Cl­[OCH2CH2N­(CH2Cl)iPr2]+ cation (15), it slowly loses H2 upon standing at 60 °C to give a metallacyclic iminium cation product 18, and it reacts with terminal alkynes to give the [Zr]-alkynyl/ammonium systems 19. The organometallic FLP 14 cleaves dihydrogen heterolytically at near to ambient conditions to give the [Zr]­H­[OCH2CH2NHiPr2]+ complex 20, which reduces benzaldehyde to the respective [Zr]­OCH2Ph product 21 and is able to transfer the H+/H– pair to styrene to give ethylbenzene. Consequently, the Zr+/amine FLP 14 was used as an active hydrogenation catalyst for a series of alkenes and internal alkynes. The catalytic hydrogenation reactions were carried out under mild conditions (r.t., 1.5 bar of H2) using between 1 and 4 mol % FLP catalyst 14.