Mono-cyclononatetraenyl lanthanide complexes.

The synthesis of the first half-sandwich complexes based on the cyclononatetraenyl (Cnt = C9H9-) ligand ([LnIII(η9-Cnt)(η3-BH4)2(thf)] (Ln = La, Ce)) is reported. The title compounds were obtained from the reaction of [Ln(BH4)3(thf)3] and [K(Cnt)]. Further solvation of [LnIII(η9-Cnt)(η3-BH4)2(thf)] with tetrahydrofuran (THF) resulted in a reversible decoordination of the Cnt ring and the formation of the ionic species [LnIII(η3-BH4)2(thf)5][Cnt]. Removal of THF from [LaIII(η9-Cnt)(η3-BH4)2(thf)] gave the polymeric compound [LaIII(µ-η2:η2-BH4)2(η3-BH4)(η9-Cnt)]n.