Oxygen-bridged and sulfur-bridged rhodium homobimetallic complexes were synthesized as air-stable crystals by using 2,6-bis(phosphanylmethyl)phenolate and -thiophenolate as the ligands, respectively. The oxygen-bridged dirhodium complex has a symmetrical structure where the carbon atom at the ipso position, oxygen, and two rhodium atoms are located in the same plane. It is thermally stable compared to the sulfur-bridged dirhodium complex and shows catalytic activity for hydrogenation of alkenes with high chemoselectivity.

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In the presence of atmospheric oxygen, O-pentafluorobenzoyloximes having a (2,4-cyclohexadienyl)Fe(CO)3 moiety at the α-position cyclize smoothly to give trans-fused [(4,5,6,7-η)-3a,7a-dihydro-3H-indole]Fe(CO)3 complexes. The cyclization proceeds via radical chain mechanism initiated by molecular oxygen, in which pentafluorobenzoyloxyl radical plays a role as a chain carrier. Thus obtained trans-fused dihydroindole iron complexes readily isomerize to the cis-fused isomers on acidic silica gel or under basic conditions. Such isomers are converted to 3a,7a-dihydroindole or indole derivatives by the oxidative removal of the Fe(CO)3 group.

Aldehydes Q 0320Hydroformylation of Monosubstituted Alkenes Catalyzed by W-Rh Bimetallic Complex. -Using a W-Rh heterobimetallic catalyst, hydroformylation of monosubstituted alkenes (I), (V), (VIII) and (XI) proceeds efficiently under atmospheric pressure of CO(II)/H2 without effecting functional groups such as disubstituted alkene moieties, aryl and alkenyl iodide functions and hydroxy and carboxy groups. -(YAMANE, M.; YUKIMURA, N.; ISHIAI, H.; NARASAKA*, K.; Chem. Lett. 35 (2006) 5, 540-541; Dep. Chem., Grad. Sch. Sci., Univ. Tokyo, Bunkyo, Tokyo 113, Japan; Eng.) -M. Paetzel 39-094

Radical Cyclization of O-Pentafluorobenzoyloximes Having a (Cyclohexadiene)Fe(CO) 3Moiety. -Reaction of arylmethyl ketoxime-tricarbonyliron complexes (I) with perfluorobenzoyl chloride provides access to the corresponding benzoyloximes which smoothly cyclize in the presence of atmospheric oxygen to give trans--fused dihydroindole-tricarbonyliron complexes. Isolation of these dihydroindole derivatives with acidic silica Wako gel B-5F provides the corresponding cis-isomers (II) due to complete isomerization. The geometry of the oxime double bond has no significance in the outcome of the cyclization reaction. Oxidative removal of the Fe(CO)3 group proceeds best after N-acyl protection [cf. (III) vs. (VII)]. -(TANAKA, K.; YUKIMURA, N.; NARASAKA*, K.; Bull. Chem. Soc. Jpn. 77 (2004) 3, 575-584; Dep. Chem., Grad. Sch. Sci., Univ. Tokyo, Bunkyo, Tokyo 113, Japan; Eng.) -Mischke 28-131