CO Fourier-transform infrared study of metallocenes on silica gel and AlPO4

Abstract

Metallocenes of vanadium, manganese, cobalt, iron and nickel have been reacted with silica gel and AlPO4. The samples were studied with CO FTIR spectroscopy. Vanadocene on AlPO4 gave a band at 1869 cm–1, interpreted as VCp2CO, and two bands from a more stable species at 2046 and 1992 cm–1, which are due to a [VCp2(CO)2]+ surface compound. Manganocene produced small amounts of a manganese carbonyl compound only after heating to 200 °C.Ferrocene reacted with the AlPO4 surface only at elevated temperatures (300 °C) giving weak CO IR bands at 2065 and 2023 cm–1. These are interpreted as due to a [FeCp(CO)2]+ species. Cobaltocene reacted similarly on both SiO2 and AlPO4. CO IR bands [from CoCp(CO)2] were observed at 2032 and 1964 cm–1(SiO2) and at 2018 and 1950 cm–1(AlPO4).Nickelocene reacted very easily with the surface of both supports. It decomposed at room temperature forming C10H12 and Ni0. At low temperatures (–80 °C) a band at 2103 (AlPO4) or 2094 cm–1(SiO2) was the main absorption band found, which is interpreted as arising from [CpNiCO]+, bonded to the surface via P—O– groups. At room temperature Ni(CO)4(CO IR band at 2056 cm–1) was formed. Only NiCp2 and FeCp2 of the metallocenes studied reacted similarly to chromocene with the two different supports. Ferrocene on the AlPO4 surface gave much weaker CO IR bands and nickelocene on the supports was less stable at room temperature than chromocene.