As scientists, we know that we should constantly question the assumptions upon which our research is based. We also know that we do not do this often enough. The recent results in f element chemistry described here should serve to remind us not to take the traditional boundaries of any area of chemistry for granted including topics as fundamental as redox chemistry and bond-length generalizations. New ways of doing reductive chemistry in the f element area as well as the synthesis of “long bond organometallics” that have unconventional bond distances and reactivity demonstrate how the “rules” in this area, thought to be true for decades, have been recently overturned. The synthetic chemistry that made these advances possible has generated additional unexpected opportunities in f element chemistry that are also described here. Overall, these results should stimulate researchers in all areas to challenge their assumptions.

The importance of questioning scientific assumptions: some lessons from f element chemistry.

Aspects of the lanthanide-carbon σ-bond

Solid-State Structures of Base-Free Ytterbocenes and Inclusion Compounds of Bis(pentamethylcyclopentadienyl)ytterbium with Neutral Carboranes and Toluene: The Role of Intermolecular Contacts

The elusive (C5Me4H)3Lu : Its synthesis and LnZ3/K/N2 reactivity

Expanding the LnZ3/Alkali‐Metal Reduction System to Organometallic and Heteroleptic Precursors: Formation of Dinitrogen Derivatives of Lanthanum

Die Trichloride von Lanthan, Neodym, Samarium und Terbium reagieren mit Na(C5Me4H) in THF zu homoleptischen Verbindungen des Typs Ln(C5Me4H)3 [Ln = La (1a), Nd (1b), Sm (1c), Tb (1d)]. Dagegen fuhrt die Reaktion von HoCl3, TmCl3 und LuCl3 mit Na(C5Me4H) nur zu den Dicyclopentadienyl-Komplexen (C5Me4H)2LnCl(THF) [Ln = Ho (2e), Tm (2f), Lu (2h)]. Die Metallocene (C5Me4H)2Ln(THF)2 [Ln = Sm (3c), Yb (3g)] sind durch Umsetzung von LnI2 (Ln = Sm, Yb) mit Na(C5Me4H) erhaltlich. Die neuen Verbindungen wurden durch 1H- und 13C-NMR-Spektren, die Tricyclopentadienylderivate 1 a und 1 c durch Rontgenstrukturanalysen charakterisiert.



Organometallic Compounds of the Lanthanides. 93. Tetramethylcyclopentadienyl Complexes of Selected 4f-Elements



The trichlorides of lanthanum, neodymium, samarium, and terbium react with Na(C5Me4H) in THF to yield the homoleptic complexes Ln(C5Me4H)3 [Ln = La (1a), Nd (1b), Sm (1c), Tb (1d)]. On the other hand the reactions of HoCl3, TmCl3, and LuCl3 with Na(C5Me4H) result only with formation of the dicyclopentadienyl complexes (C5Me4H)2LnCl(THF) [Ln = Ho (2e), Tm (2f), Lu (2h)]. The metallocenes (C5Me4H)2Ln(THF)2 [Ln = Sm (3c), Yb (3g)] are obtained by the reactions of LnI2 (Ln = Sm, Yb) with Na(C5Me4H). The 1H- and 13C-NMR spectra as well as the X-ray crystal structure of the triscyclopentadienyl complexes 1 a and 1 c are discussed.

F. Ekkehard Hahn

Papers

Metallorganische Verbindungen der Lanthanoide. 93 [1]. Tetramethylcyclopentadienyl‐Komplexe ausgewählter 4f‐Elemente