A combination of readily available α-diimine (DI) ligands with air- stable nickel(II) bis(carboxylates) generated, following activation with a borane reagent, an active catalyst for the hydrogenation of alkenes. At 50 °C and 4 atm of H2 pressure, this platform is an effective precatalyst for the hydrogenation of tri- and tetrasubstituted, unfunctionalized alkenes, some of the most challenging substrate classes for homogeneous hydrogenation. Catalysis was also initiated using the organometallic nickel precursors, (iPrDI)Ni(allyl) and the dimeric hydride, [(iPrDI)NiH]2 (iPrDI = ArN=C(Me))2, Ar = 2,6-iPr2−C6H3). Investigations into activation of the nickel bis(carboxylate) established formation of the nickel hydride upon treatment with with HBPin (Pin = pinacolate). Electronic structure calculations and EPR spectroscopic studies support formation of a nickel(II) complex with a one electron reduced α-diimine ligand. The scope of the hydrogenation protocol and catalyst optimization studies will also be presented.

Hydrogenation of hindered, unfuctionalized alkenes using redox-active α-diimine nickel catalysts

254th National Meeting (2017)

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