Platinum Metals Rev., 2001, 45, (2), 59
Biomimetic Chiral Rhodium Catalysis
Recent attempts to mimic the high activity of metalloenzymes involve the molecular imprinting of organometallic systems. This involves a polymerisation reaction in which a pseudosubstrate is attached to a catalyst centre. On removal a shape-selective cavity is left.
Researchers at the Institut für Anorganische Chemie der Ludwig-Maximilians-Universität, Germany, now report a highly active and selective (ee > 99%) chiral Rh(III) catalyst which can asymmetrically reduce acetophenone (K. Polborn and K. Severin, Eur. J. Inorg. Chem ., 2000, (8), 1687–1692). The organometallic Cp*Rh complex had a chiral N, N′ -chelate ligand with a styrene side chain; the remaining coordination site was occupied by a methylphenylphosphinato ligand – the pseudosubstrate which mimics acetophenone. During molecular imprinting, the Rh complex was co-polymerised with ethylene glycol dimethacrylate; the phoshinato ligand in the resulting polymer was then replaced by a chloro ligand to generate a shape-selective cavity near the active rhodium centre.