Cyclic Distannene or Bis(stannylene) with a Ferrocenyl Backbone: Synthesis, Structure, and Coordination Chemistry

1,1'-Dilithioferrocene was reacted with 2 equiv of isopropyl (Ar*) or methyl (Ar') substituted terphenyl tin(II) chloride. Reaction product 1, carrying the bulkier terphenyl substituent Ar*, displays a bis(stannylene) structure in the solid state without formation of a tin-tin bond. Temperature-dependent solution ¹¹⁹Sn NMR spectroscopy, however, revealed a dynamic interplay between bis(stannylene) (100 °C) and cyclic distannene (-80 °C). In contrast to 1, the less bulky Ar' substituent results in a cyclic distannene 2. On the basis of temperature-dependent ¹¹⁹Sn NMR spectroscopy the Sn-Sn bond of compound 2 was preserved up to 100 °C. Both compounds were further characterized by solid-state ¹¹⁹Sn NMR spectroscopy as well as ¹¹⁹Sn and ⁵⁷Fe Mössbauer spectroscopy. 1 reacted as a chelating ligand with nickel and palladium complexes [Ni(cod)₂] and [Pd(nbe)₃] (nbe = norbornene). In the resulting coordination compounds the nonstabilized stannylene acts as a donor as well as an acceptor ligand and shows a dynamic switch from donor to acceptor behavior in the monopalladium complex.