Mono-cyclononatetraenyl lanthanide complexes.

The synthesis of the first half-sandwich complexes based on the cyclononatetraenyl (Cnt = C 9 H 9 - ) ligand ([Ln III ( η 9 -Cnt)( η 3 -BH 4 ) 2 (thf)] (Ln = La, Ce)) is reported. The title compounds were obtained from the reaction of [Ln(BH 4 ) 3 (thf) 3 ] and [K(Cnt)]. Further solvation of [Ln III ( η 9 -Cnt)( η 3 -BH 4 ) 2 (thf)] with tetrahydrofuran (THF) resulted in a reversible decoordination of the Cnt ring and the formation of the ionic species [Ln III ( η 3 -BH 4 ) 2 (thf) 5 ][Cnt]. Removal of THF from [La III ( η 9 -Cnt)( η 3 -BH 4 ) 2 (thf)] gave the polymeric compound [La III ( μ-η 2 :η 2 -BH 4 ) 2 ( η 3 -BH 4 )( η 9 -Cnt)] n .