Redox transmetallation approaches to the synthesis of extremely bulky amido-lanthanoid(II) and -calcium(II) complexes

Redox transmetallation protolysis reactions between HgPh₂, elemental metals, M = Ca, Eu, or Yb, and the bulkyl arylsilylamine ^PhL^†H (HN(SiPh₃)(Ar^†), Ar^† = C₆H₂Prⁱ{C(H)Ph₂}₂-4,2,6), or the borylsilylamine ^PhL^BoH (HN(SiPh₃){B(DipNCH)₂}, Dip = C₆H₃Prⁱ ₂-2,6) pro-ligands yielded complexes incorporating doubly deprotonated, N,C-chelating amido/organyl ligands, viz. [M(L^-H) (thf)_x]_n, L^-H = ^PhL^†-H (1-3) or ^PhL^Bo-H (4-5); M = Ca (1, 4), Eu (2) or Yb (3, 5); x = 0 (5) or 2 (1-4); n = 1 (1-4) or 2 (5). Structural differences between 4 and 5 represent a rare divergence in the chemistry of divalent calcium and ytterbium. Utilisation of a less hindered bis(aryl) amine, ^DL^MH (HN(Dip)(Mes), Mes = C₆H₂Me₃-2,4,6) in a similar reaction yielded a three-coordinate, trigonal planar ytterbium complex [Yb(^DL^M)₂(thf)] (6). Direct redox transmetallation reactions between an amido-mercurial iodide [(^MeL^†)HgI] (7, ^MeL^† =-N(SiMe₃)(Ar^†)) and ytterbium or europium metal afforded homoleptic [Yb(^MeL^†)₂] (8) and heteroleptic [{Eu(^MeL^†)(μ-I)(thf)}₂] (9) respectively. This study highlights the versatility of redox transmetallation pathways to amido-lanthanoid complexes, especially where such compounds are difficult to access using conventional salt metathesis pathways.