SYNTHESIS AND STRUCTURE OF ACYLCARBONYLINDENYL(PHOSPHINE) IRON(II) COMPLEXES - ANALYSIS OF LIGAND EFFECTS IN AN INDENYL SYSTEM

The reactions of (C9H7)Fe(CO)2R (R = CHMe2, Me) with phosphines and phosphites (L) yield two series of indenyl complexes (C9H7)Fe(CO)(COR)(L) via the migratory insertion process. The acyl complexes provide a case of diastereotopic shielding by an asymmetric iron atom. The phosphorus ligands exert electronic effects on the terminal carbonyl group of the methyl complexes that are essentially the same in the indenyl system and in the analogous cyclopentadienyl system. Substitution of methyl for isopropyl in the acyl moiety increases pi-back bonding from iron to carbonyl. The structure of (C9H7)Fe(CO)(COCHMe2)(PPh3) has been determined by X-ray analysis, and exhibits a distorted eta5 coordination of the indenyl ligand [slip value = 0.122 angstrom (mean d(Fe-C(3a), C(7a)) - mean d(Fe-C(1), C(3))].