PREPARATION OF ETA(5)-PYRANYLTRICARBONYLMANGANESE COMPLEXES AND PYRYLIUM TRIIODIDE SALTS FROM CYCLOMANGANATED CHALCONES AND ALKYNES

Derivatives of [[1-phenyl-2-phenylcarbonyl-kappa O]ethenyl-kappa C-1]t etracarbonylmanganese, i.e. chalcone (1,3-diphenylprop-2-en-1-one) cyc lomanganated at the beta-position, undergo insertion reactions with al kynes under reflux in carbon tetrachloride to give [2,4-diphenyl-pyran yl-eta(5)]Mn(CO)(3) derivatives, the reaction being highly regioselect ive in the case of unsymmetrical alkynes. Reaction of the pyranyl-Mn(C O)(3) complexes with iodine in carbon tetrachloride gives pyrylium tri iodide salts in excellent yield. The reaction of one pyranyl complex, romethylphenyl)pyranyl-eta(5)]tricarbonylmanganese (2d), with Na[Fe(CO )(2)Cp], gave the demetallated ring-opened isomers thylphenyl)-5-(4-ch lorophenyl)penta-2,4-dien-1-one (10a) and rifluoromethylphenyl)-5-phen ylpenta-2,4-dien-1-one (10b). X-ray crystal structure determinations o f yl-4,6-diphenylpyranyl-eta(5)]tricarbonylmanganese (5) and 2,6-diphe nyl-4-(4-trifluoromethylphenyl)pyrylium triiodide (3b) are described, the former being the first reported for a pyranyl-eta(5) metal complex .