Terminal dysprosium and holmium organoimides

Abstract

Terminal rare-earth-metal imide complexes Tp^tBu,MeLn(NC₆H₃iPr₂-2,6)(dmap) of the mid-late rare-earth elements dysprosium and holmium were synthesized via double methane elimination of Lewis acid stabilized dialkyl precursors Tp^tBu,MeLnMe(GaMe₄) with primary aniline derivative H₂NC₆H₃iPr₂-2,6 (H₂NAr^iPr). Exploiting the weaker Ln–CH₃⋯[GaMe₃] interaction compared to the aluminium congener, addition of the aniline derivative leads to the mixed methyl/anilido species Tp^tBu,MeLnMe(HNAr^iPr) which readily eliminate methane after being exposed to the Lewis base DMAP (N,N-dimethyl-4-aminopyridine). Under the same conditions, [AlMe₃]-stabilized dimethyl rare-earth-metal complexes transform immediately to Lewis acid bridged imides Tp^tBu,MeLn(μ₂-NC₆H₃Me₂-2,6)(μ₂-Me)AlMe₂ (Ln = Dy, Ho). DMAP/THF donor exchange is accomplished by treatment of Tp^tBu,MeLn(NC₆H₃iPr₂-2,6)(dmap) with 9-BBN in THF while the terminal imides readily insert carbon dioxide to afford carbamate complexes.