Solventless substitution chemistry of iron and ruthenium metal carbonyl complexes

Abstract

ABSTRACT Solventless reactions of substituted cyclopentadienyl metal carbonyls of iron and ruthenium with electron donor ligands have been carried out. The reactions between CpFe(CO)2I and a range of phosphine ligands occurred in melt phase and yielded two typical compounds : salt product, [CpFe(CO)2PR3]I, and non-salt product, CpFe(CO)PR3I with the salt product being predominant. The complex [CpFe(CO)2]2 was used to catalyze these reactions. The progress of the reactions was followed by 1H NMR spectroscopy. The characterization of products correlates well with the products obtained when working in solution medium. The presence of a Me substituent on the Cp ring was found to favour the salt product formation but generally led to lower rates of reaction. Solventless reactions between RCpRu(CO)2I (R = H, Me) and solid phosphine ligands were also carried out. It has been observed that the ruthenium complexes were less reactive compared with their iron analogues but led to the same types of products namely salt and non-salt. The phosphite ligands were found to be less reactive than their phosphine analogues. In fact, the solventless reactions between RCpM(CO)2I (R = H, Me; M = Fe, Ru) were very slow even in the presence of [CpFe(CO)2]2 as a catalyst. However, when Me3NO.2H2O was added to the reaction mixture in solventless conditions, the non-salt product was obtained in a short period of time at 80oC. A range of cyclopentadienyl based metal complexes e.g [CpMo(CO)3]2, [MeCpRu(CO)2]2 etc. and palladium based compounds such as PdO, Pd/CaCO3 5% etc. were found to be good catalysts for the solventless reactions between CpFe(CO)2I and PPh3. Solventless migratory-insertion reactions have been successfully conducted between CpFe(CO)2CH3 and a range of solid phosphine ligands. Only the acetyl products, CpFe(CO)[PR3]COCH3 were obtained. SO2 insertion into RCpFe(CO)2R’ (R = H, CH3; R’ = CH3, CH2Ph) occurred quite easily at room temperature. However, when R was a carboxylic acid group, CO2H, no reaction took place. CO insertion into the same systems did not happen in solventless conditions.