Cyclopentadienyl complexes with pendant phosphane ligands combine two of the most common ligand classes of organometallic chemistry in one ligand system.[1] The basic idea of this chemistry is the possibility of a temporary decomplexation of the phosphane ligand thereby creating a vacant coordination site at the metal. While other groups investigated such systems with rhodium,[2] iron[3] or iridium[4] as the metal, we focused on cobalt and, more recently, on nickel. Complexes 1-5 are relevant examples, which will be discussed in the lecture. Cobalt complexes such as 1-3 can be obtained with unusual and rare ligand systems and are often not available with an independent phosphane ligand instead of the tether. While we used a di-tert-butylphosphanylethyl tether some time ago, we more recently became interested in less stable nickel complexes with a secondary phosphane tether, of which 5 is one of the first example for a late transition metal[5].

[1] H. Butenschön, Chem. Rev. 2000, 100, 1527-1564.
[2] I. Lee, F. Dahan, A. Maisonnat, R. Poilblanc, Organometallics 1994, 13, 2743-2750.
[3] T.-F. Wang, J.-P. Juang, Y.-S. Wen, J. Organomet. Chem. 1995, 502, 117-128.
[4] T. A. Mobley, R. G. Bergman, J. Am. Chem. Soc. 1998, 120, 3253-3254.
[5] I. Werner, H. Butenschön, Eur. J. Inorg. Chem. 2014, 6051-6060