A series of air-stable, nitrile-ligated (cyclopentadienone)iron dicarbonyl compounds was synthesized and their activities as catalysts in the transfer reduction of acetophenone were explored. While all were active catalysts, the acetonitrile adduct was chosen for further study and was found to be active in the transfer reduction of aldehydes and ketones and in the Oppenauer-type oxidation of secondary alcohols. The acetonitrile catalyst exhibited activities similar to those of an analogous air-sensitive iron hydride, but unlike the iron hydride it was unreactive in carbonyl reductions using hydrogen gas.
Productivity for the hydrogenation of CO 2 to formic acid was increased with the addition of catalytic amounts of KHCO 3 and other common inorganic salts. Mechanistic experiments revealed that the reaction likely proceeds via the formation of a metal− carbonate species. The effect was general for many noble-metal catalysts and for one of the most efficient non-noble-metal hydrogenation catalysts.
In contrast to high spin pyridyl diimine iron(ii) dichloride complexes, analogous bis(amidinato)-N-heterocyclic carbene iron(ii) and iron(iii) complexes demonstrate complex magnetic behaviour. In the solid state, they are best described as intermediate spin complexes at low temperatures that demonstrate gradual spin transitions beginning near or below room temperature. Treating the bis(amidinato)-N-heterocyclic carbene iron(ii) complex with an aryl azide revealed enhanced reactivity compared to analogous complexes supported by pyridyl diimine ligands.
previous synthesis and characterization of the key nitrile-ligated (cyclopentadienone)iron dicarbonyl complex 7 was overlooked. Knçlker and co-workers published the synthesis and full characterization of acetonitrile(dicarbonyl)iron 7 already in 1999.[1] The corresponding diacetonitrile(carbonyl)iron and (triacetonitrile)iron complexes were also reported in that publication. Synthesis of these acetonitrile-iron complexes was achieved by photochemically-induced ligand exchange starting from the (tricarbonyl)iron complex.[1]
Five iron complexes of type (I) differing in the nitrile ligand are prepared and found to be active catalysts in the transfer reduction of acetophenone.
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