Metallcarbonyl-synthesen : V. Die reduktive hochdruckcarbonylierung von (η5-C5H5)NbCl4 als einfache und leistungsfähige synthesemethode für (η5-C5H5) Nb(CO)4. Darstellung der isotopenmarkierten derivate (η5-C5H5) Nb(CO)4 ? n(13CO)n und (η5-C5H5) Nb(CO)4 ? n(13C18O)n

The reductive high-pressure carbonylation of tetrachloro(η⁵-cyclopentadienyl)niobium using sodium as reduction agent and Cu/Al mixture as halogen acceptor system cleanly yields tetracarbonyl (η⁵-cyclopentadienyl)niobium which can be synthesized by means of this new procedure on a 35 g-scale, with yields ranging between 89 and 94%. Under photolysis conditions, (η⁵-C₅H₅) Nb(CO)₄ is converted into the solvent complex (η⁵-C₅H₅) Nb(CO)₃THF which, in turn, incorporates ¹³Co or ¹³C¹⁸O under mild conditions to give the labelled derivatives (η⁵-C₅H₅) Nb(CO)_{4 ? n}(¹³CO)_n and (η⁵-C₅H₅) Nb(CO)_{4 ? n}(¹³C¹⁸O)_n, respectively.