Calcium Hydride Catalysts for Olefin Hydrofunctionalization: Ring-Size Effect of Macrocyclic Ligands on Activity.

ABSTRACT: The fifteen-membered NNNNN macrocycle Me₅ PACP (Me₅ PACP=1,4,7,10,13-pentamethyl-1,4,7,10,13-pentaazacyclopentadecane) stabilized the [CaH]⁺ fragment as a dimer with a distorted pentagonal bipyramidal coordination geometry at calcium. The hydride complex was prepared by protonolysis of calcium dibenzyl with the conjugate acid of Me₅ PACP followed by hydrogenolysis or treating with ⁿ OctSiH₃ of the intermediate calcium benzyl cation. The calcium hydride catalyzed the hydrogenation and hydrosilylation of unactivated olefins faster than the analogous calcium complex stabilized by the twelve-membered NNNN macrocycle Me₄ TACD (Me₄ TACD=1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane). Kinetic investigations indicate that higher catalytic efficiency for the Me₅ PACP stabilized calcium hydride is due to easier dissociation of the dimer in solution when compared to the Me₄ TACD analogue.

SUBMITTER: Hollerhage T 

PROVIDER: S-EPMC7898310 | biostudies-literature | 2021 Feb

REPOSITORIES: biostudies-literature