Synthesis, structure determination and chemoselective catalytic studies of amino acids complexes of osmium(II)

Abstract The two new half sandwich amino acids complexes of osmium, i.e. [Os(η6‐ p ‐cymene)(κ1‐ N ‐(rac)‐phenylglycine methylester)Cl 2 ] ( A ) and [Os(η6‐ p ‐cymene)(κ1‐ N , N ′‐( S )‐phenylalanineamido)Cl] ( B ) have been synthesized and employed for chemoselective reduction of ketones (nine α,β‐unsaturated ketones and three saturated ketones). The complexes were characterized by spectroscopic as well as analytical methods; their solid structures were confirmed by single‐crystal X‐ray analysis. Both of the osmium complexes catalyze the reduction of α,β‐unsaturated ketones to saturated ketones via isomerization of the initially produced allylic alcohols. The reducible substrates were studied to obtain information on the steric and electronic factors which may affect the interaction of the substrate with the metal center and, thus, control the selectivity of the hydrogen‐transfer reductions. Copyright © 2008 John Wiley & Sons, Ltd.