Haloalkyl complexes of the transition metals: VI. A study of the reactions of halomethyldicarbonylcyclopentadienyliron complexes with some tertiary phosphine, amine and sulphur ligands

Abstract

The reactions of [CpFe(CO) 2CH 2X] with a series of tertiary phosphines, amines, and SMe 2 have been investigated in both CH 3CN and THF (Cp = η 5-C 5H 5 and X = Cl, Br or I). Two types of cationic products, namely the ylide complexes [CpFe(CO) 2CH 2L] + or the disubstituted complexes [CpFe(CO)L 2] +, were obtained, depending on the halide (X), the ligand (L) and the solvent used. The reactions of [CpFe(CO) 2CH 2L]Br with L in CH 3CN gave [CpFe(CO)L 2]Br for L = PMe 3 and PMe 2Ph, suggesting that [CpFe(CO) 2CH 2L] + is an intermediate in the formation of [CpFe(CO)L 2] + from [CpFe(CO) 2CH 2X] on reaction with L. The relative rates of reaction of [CpFe(CO) 2CH 2Br] with L were determined by 1H NMR spectroscopy, and the rate found to increase with increasing p K a and decreasing cone angle of L. PBu t 3 was found not to react with [CpFe(CO) 2CH 2Cl] under any of the conditions used, although it readily reacts with [CpFe(CO) 2CH 2Br] to form the cationic ylide complex. In general, the rate of reaction of [CpFe(CO) 2CH 2X] with L increases in the sequence Cl < Br < I. The reaction of [CpFe(CO) 2CH 2Br] with bis(diphenylphosphino)ethane yields a bridged dicationic ylide complex [Cp(CO) 2FeCH 2P(Ph) 2(CH 2) 2P(Ph) 2CH 2Fe(CO) 2Cp] 2+.