Complexes (SalprentBu,tBu)Y[N(SiHMe2)2](thf) and (SALENtBu,tBu)La[N(SiHMe2)2](thf) (SALENtBu,tBu= SalcyctBu,tBuand SalprentBu,tBu) were prepared from Ln[N(SiHMe2)2]3(thf)2and H2SALENtBu,tBu. The yttrium complex was characterized by X-ray crystallography revealing intrinsic solid-state structural features: the metal centre is displaced by 1.05 Å from the [N2O2] least squares plane of a highly bent SalprentBu,tBuligand (∠(Ph,Ph) dihedral angle of 80.4(1)°) and is coordinated asymmetrically by the silylamide ligand exhibiting one significant Y(HSi) β-agostic interaction (Y–N1–Si1, 106.90(9)°; YSi1, 3.2317(6) Å). Complexes (SALENtBu,tBu)Ln[N(SiHMe2)2](thf)n(n = 1, Sc; n = 2, Y, La) react with ammonium tetraphenylborate to form the ion pairs [(SALENtBu,tBu)Ln(thf)n][BPh4]. The cationisation was proven by X-ray crystal structure analyses of [(SalprentBu,tBu)Sc(thf)2][B(C6H5)4]·2(thf) and [(SalprentBu,tBu)Ln(thf)3][B(C6H5)4]·4(thf) (Ln = Y, La), showing an octahedral and pentagonal-bipyramidal coordination geometry, respectively. [ABSTRACT FROM AUTHOR]