β-Diiminatolanthanoid(III) halides revisited

The crystalline compounds [LnCl 2 ( L )(thf) 2 ] [Ln = Ce ( 1 ), Tb ( 2 ), Yb ( 3 )], [NdI 2 ( L )(thf) 2 ] ( 4 ), [LnCl( L′ ) 2 ] [Ln = Tb ( 5 ), Yb ( 6 ) (a known compound)] and [YbCl( L′′ )(μ-Cl) 2 Li(OEt 2 ) 2 ] ( 7 ) have been prepared [ L  = {N(C 6 H 3 Pr i 2 -2,6)C(H)} 2 CPh, L′  = {N(SiMe 3 )C(Ph)} 2 CH, L′′  = {N(SiMe 3 )C(C 6 H 4 Ph-4)} 2 CH]. The X-ray molecular structures of 2 – 7 have been established; in each, the monoanionic ligand L , L′ or L′′ is N , N ′-chelating and essentially π-delocalised. Each of 1 – 7 was prepared from the appropriate LnCl 3 , or for 4 [NdI 3 (thf) 2 ], and an equivalent portion of the appropriate alkali metal [Li for 7 , Na for 2 , 3 and 5 , or K for 1 , 4 and 6 ] β-diiminate in thf; the isolation of exclusively 5 and 6 (rather than the L′ analogues of 2 or 3 ) is noteworthy, as is the structure of 7 which has no precedent in Group 3 or 4f metal β-diiminato chemistry.