Chemical engineers ensure the efficiency and safety of chemical processes, adapt the chemical make-up of products to meet environmental or economic needs, and apply new technologies to improve existing processes. name: 1,5-Diphenylpenta-1,4-dien-3-one,
Different rhodium(III) complexes [Rh(C,C)(P,P)X2]+ bearing both a cis-chelating dicarbene and a diphosphine ligand were synthesized (C,C = methylene(4,4?-diimidazolylidene); P,P = 1,2-bis(diphenylphosphino)ethane (dppe), (R)-(+)-2,2?-bis(diphenylphosphino)-1,1?-binaphthalene (R-BINAP); X = halide, carbanion, NCMe). Solution analysis by NMR spectroscopy indicate a dynamic behavior of the complexes and cis/trans isomerization processes, likely through dissociation of the nonchelating ligands X (X = halide, NCMe), and eventually also involving the diphosphine ligand, identified by the formation of phosphine oxides. The presence of a diphosphine ligand in addition to the dicarbene substantially enhances the catalytic activity of the rhodium center in the transfer hydrogenation of ketones in iPrOH/KOH, reaching over 4000 turnover numbers and turnover frequencies around 1000 h-1 vs 330 h-1 for the phosphine-free analogue. Optimization of the catalytic conditions allowed transfer hydrogenation to be run with only 1 mol % base instead of the often used 10 mol %. The chiral R-BINAP ligand enhances catalytic activity, though no enantioselectivity was induced in the transfer hydrogenation of fluoroacetophenone as prochiral substrate.
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Reference：
Synthesis and Crystal Structure of a Chiral C3-Symmetric Oxygen Tripodal Ligand and Its Applications to Asymmetric Catalysis,
Chiral lanthanide(III) complexes of sulphur–nitrogen–oxygen ligand derived from aminothiourea and sodium D-camphor-β-sulfonate