Chromiumtricarbonyl arenes

Asymmetric induction of between 30 and 66% has been reported for the addition of perfluoroalkyl iodides to chiral arene/chromiumtricarbonyl complexes using ultraso-nically dispersed zinc at room temperature (Scheme 3.19) [101], Photochemical decomposition of the organometallic intermediate affords a chiral alcohol product. The reaction is carried out in DMF as solvent and high overall yields are reported e.g.80 % (R = Et). Only a small excess of the perfluoroalkyl iodide is required and the conversion is complete in under 1 h. 

Not all carbon nucleophiles will add to arene chromiumtricarbonyl complexes. For example, alkyllithium reagents and simple ketone enolates do not give adducts.198... 

Examples of non-platinum metal hydrogenation catalysts include (arene)-chromiumtricarbonyls which will hydrogenate dienes, alkynes, and so on, while ReH7(PCy3)2 will selectively hydrogenate acenaphthalene. Lanthanides and early transition metals are discussed later. Those catalysts operate via non-radical processes, but a few systems are known to involve radical reactions. The complex [CoH(CN)5]3 is a water-soluble catalyst that is selective for the hydrogenation of ajS-unsaturated compounds. 

Chromium, Molybdenum and Tungsten The intramolecular rotational behaviour of a series of highly substituted Ti -arene chromium and molybdenum compounds has been examined in detail. Dynamic processes in the solid state, using spin-lattice relaxation time measurements, have been studied for two structurally characterised polymethyl benzenechromium tricarbonyl complexes. The mechanism of migration of the Cr(CO)3 unit from the six to the five membered ring in indenyl anions has been reported. The synthesis and cyclic voltammetry of (Ti -phenylmethylsila-14-crown-5)chromiumtricarbonyl has appeared. ... 

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