Rare‐Earth‐Metal Methyl,Amide, and Imide Complexes Supported by a Superbulky Scorpionate Ligand

The reaction of monomeric (Tp^tBu,Me)LuMe₂] (Tp^tBu,Me=tris(3‐Me‐5‐tBu‐pyrazolyl)borate) with primary aliphatic amines H₂NR (R=tBu, Ad=adamantyl) led to lutetium methyl primary amide complexes (Tp^tBu,Me)LuMe(NHR)], the solid‐state structures of which were determined by XRD analyses. The mixed methyl/tetramethylaluminate compounds (Tp^tBu,Me)LnMe({μ₂‐Me}AlMe₃)] (Ln=Y, Ho) reacted selectively and in high yield with H₂NR, according to methane elimination, to afford heterobimetallic complexes: (Tp^tBu,Me)Ln({μ₂‐Me}AlMe₂)(μ₂‐NR)] (Ln=Y, Ho). X‐ray structure analyses revealed that the monomeric alkylaluminum‐supported imide complexes were isostructural, featuring bridging methyl and imido ligands. Deeper insight into the fluxional behavior in solution was gained by ¹H and ¹³C NMR spectroscopic studies at variable temperatures and ¹H–⁸⁹Y HSQC NMR spectroscopy. Treatment of (Tp^tBu,Me)LnMe(AlMe₄)] with H₂NtBu gave dimethyl compounds (Tp^tBu,Me)LnMe₂] as minor side products for the mid‐sized metals yttrium and holmium and in high yield for the smaller lutetium. Preparative‐scale amounts of complexes (Tp^tBu,Me)LnMe₂] (Ln=Y, Ho, Lu) were made accessible through aluminate cleavage of (Tp^tBu,Me)LnMe(AlMe₄)] with N,N,N′,N′‐tetramethylethylenediamine (tmeda). The solid‐state structures of (Tp^tBu,Me)HoMe(AlMe₄)] and (Tp^tBu,Me)HoMe₂] were analyzed by XRD.