Gehinderte Ligandbewegungen in Übergangsmetallkomplexen, XXXVII [1]: Photoreaktion von Dekacarbonyldirhenium mit Phenylallen / Hindered Ligand Motions in Transition Metal Complexes, XXXVII [1]: Photoreaction of Decacarbonyldirhenium with Phenylallene

Abstract

Decacarbonyldirhenium (1) and phenylallene (2) form upon U V irradiation four dinuclear complexes: Decacarbonyl-//-^l:l-(3,4-diphenyl-1,5-hexadien-2,5-diyl)-dirhenium (3), enneacarb on yl-//V :3-(3-phenyl-2-propen-l,2-diyl)-dirhenium (4), octacarb on yl-//-h yd rid o-/iV 2-(3-phenyl-l,2-propadien-l-yl)-dirhenium (5) and octacarbonyl-/i-?72 2-(phenyl-l,2-propadiene)-dirhenium (6). The thermolabile complex 4 looses CO and forms the phenylallene bridged compound 6. Similarly 5 is rearranged to 6 by transfer o f the hydrido ligand to the 3-phenyl-1,2-propadien-l-yl bridge. The formation o f 3 and 4 can be rationalized via pentacarbonyl-phenylpropenediyl-rhenium radicals which dimerize to give 3 or add pentacarbonylrhenium radicals, loose CO and form 4. The crystal and molecular structure o f 3 was deter mined by X-ray structure analysis. In the solid state the molecule is present in the ± ap confor mation. In solution at 233 K the ± a p , +sc, and -s c conform ations are equally populated. By a hindered rotation around a CC single bond, the three conformers are interconverted with a rotation barrier o f J G * 25g = 52.3 ± 1 k J -m o L 1.