Photolysereaktionen mit Komplexen des Typs CpFe(CO)2R (R = Me, Et, Ph)+ / Photolytic Reactions with Complexes of the Type CpFe(CO)2R (R = Me, Et, Ph)+

Abstract

Photolysis of CpFe(CO)2R complexes [R = Me (1a), Et (1b), Ph (1c)] in hydrocarbon solvents results in loss of the group R and formation of the binuclear compound [CpFe(CO)2]2 (2). In the case of 1a, the photogenerated methyl group reacts to give methane by intramolecular hydrogen abstraction from the Cp ring, or by intermolecular hydrogen abstraction either from the solvent or another methyl group. The photoinduced dealkylation of the ethyl compound 1b is explained by β-elimination (to give ethylene) and subsequent reaction of the hydrido intermediates thus formed with unchanged 1b (to give ethane). The photolysis of 1c leads to phenyl groups which abstract hydrogen from the solvent to give benzene; a noticeable amount of diphenyl is also observed if benzene is used as a solvent. In the presence of potential two-electron ligands L [L = PMe3, P(OMe)3], only the carbonyl groups of CpFe(CO)2Me (1a) are photolabile, and substituted derivatives of the type CpFe(CO)(L)Me [L = PMe3 (3a), P(OMe)3 (4a)] and CpFe(L)2Me [L = P(OMe)3 (5a)] are formed. The photoinduced reaction of CpFe(CO)2Me (1a) and diphenylacetylene in solution gives metallocyclic derivatives containing either one or two diphenylacetylene units. On the basis of the IR, the 1H and 13C NMR, and the mass spectra, the complex CpFe(CO)(Ph2C2-COMe) (6a) is assigned a structure containing a vinyl-ketone unit in a five-membered metallocycle, while in CpFe(Ph4C4-COMe) (7a) a tetraphenylbutadienyl group appears to be incorporated into a seven-membered metallocycle