Mononuclear calcium complex as effective catalyst for alkenes hydrogenation

Abstract

Hydrogenolysis of the scorpionate-supported calcium benzyl complex [(Tp^Ad,iPr)Ca(p-CH₂C₆H₄-Me)(THP)] (Tp^Ad,iPr = hydrotris(3-adamantyl-5-isopropyl-pyrazolyl)borate, THP = tetrahydropyran) (2-THP) afforded the mononuclear calcium hydrido complex [(Tp^Ad,iPr)Ca(H)(THP)] (3). Under mild conditions (40 °C, 10 atm H₂, 5 mol% cat.), complex 3 effectively catalyzed the hydrogenation of a variety of alkenes, including activated alkenes, semi-activated alkenes, non-activated terminal and internal alkenes. Mononuclear calcium unsubstituted alkyl complex [(Tp^Ad,iPr)Ca{(CH₂)₄Ph}(THP)] (6), proposed as the catalytic hydrogenation intermediate, was isolated and structurally characterized.