Ligand substitution and electronic structure studies of bis(phosphine)cobalt cyclooctadiene precatalysts for alkene hydrogenation

Diene self-exchange reactions of the 17-electron, formally cobalt(0) cyclooctadienyl precatalyst, (R,R)-(iPrDuPhos)Co(COD) (P2CoCOD, (R,R)-iPrDuPhos = 1,2-bis((2R,5R)-2,5-diisopropylphospholano)benzene, COD = 1,5-cyclooctadiene) were studied using natural abundance and deuterated 1,5-cyclooctadiene. Exchange of free and coordinated diene was observed at ambient temperature in benzene-d6 solution and kinetic studies support a dissociative process. Both neutral P2CoCOD and the 16-electron, cationic cobalt(I) complex, [(R,R)-(iPrDuPhos)Co(COD)][BArF4] (BArF4 = B[(3,5-(CF3)2)C6H3]4) underwent instantaneous displacement of the 1,5-cyclooctadiene ligand by carbon monoxide and generated the corresponding carbonyl derivatives. The solid-state parameters, DFT-computed Mulliken spin density and analysis of molecular orbitals suggest an alternative description of P2CoCOD as low-spin cobalt(II) with the 1,5-cyclooctadiene acting as a LX2-type ligand. This view of the electronic structure provides insight into the nature of the ligand substitution process and the remarkable stability of the neutral cobalt complexes toward protic solvents observed during catalytic alkene hydrogenation.

E. coli Nickel-Iron Hydrogenase 1 Catalyses Non-native Reduction of Flavins: Demonstration for Alkene Hydrogenation by Old Yellow Enzyme

<p>Robust [NiFe] hydrogenase 1 (Hyd1) from <i>Escherichia coli</i> is shown to have non-native, H₂-dependent activity for FMN and FAD reduction, and to function as a promising recycling system for FMNH₂ supply to flavoenzymes for chemical synthesis, giving a total turnover number over 10 thousand when coupled with an Old Yellow Enzyme ene reductase. </p>

E. coli Nickel-Iron Hydrogenase 1 Catalyses Non-native Reduction of Flavins: Demonstration for Alkene Hydrogenation by Old Yellow Enzyme

<p>Robust [NiFe] hydrogenase 1 (Hyd1) from <i>Escherichia coli</i> is shown to have non-native, H₂-dependent activity for FMN and FAD reduction, and to function as a promising recycling system for FMNH₂ supply to flavoenzymes for chemical synthesis, giving a total turnover number over 10 thousand when coupled with an Old Yellow Enzyme ene reductase. </p>

E. coli Nickel-Iron Hydrogenase 1 Catalyses Non-native Reduction of Flavins: Demonstration for Alkene Hydrogenation by Old Yellow Enzyme

<p>Robust [NiFe] hydrogenase 1 (Hyd1) from <i>Escherichia coli</i> is shown to have non-native, H₂-dependent activity for FMN and FAD reduction, and to function as a promising recycling system for FMNH₂ supply to flavoenzymes for chemical synthesis, giving a total turnover number over 10 million when coupled with an Old Yellow Enzyme ene reductase. </p>

Mononuclear calcium complex as effective catalyst for alkenes hydrogenation

Mononuclear calcium unsubstituted alkyl complex [(TpAd,iPr)Ca{(CH2)4Ph}(THP)], proposed as the catalytic alkene hydrogenation intermediate, was isolated for the first time.

Metal free alkene hydrogenation by B-doped graphitic carbon nitride

Metal free hydrogenation of styrene under mild conditions employing boron-doped carbon nitride catalysts is reported.