Scandium and yttrium complexes of the diamide–diamine donor ligand (2-C5H4N)CH2N(CH2CH2NSiMe3)2: chloride, primary and secondary amide, benzamidinate and alkyl functionalised derivatives

Abstract

Five- and six-coordinate scandium and yttrium complexes of the recently described diamide–diamine donor ligand N₂NN′ (where H₂N₂NN′ = (2-C₅H₄N)CH₂N{CH₂CH₂N(H)SiMe₃}₂) are described. Reaction of ScCl₃ with Li₂N₂NN′ gave five-coordinate [ScCl(N₂NN′)] 1 in excellent yield. The corresponding reaction with YCl₃ in tetrahydrofuran (thf) or pyridine (py) solution afforded “ate” complexes best described as [YCl(N₂NN′)(L)]·1.5(LiCl) (L = thf 2 or py 3). The two chloride complexes 1 and 2 are useful starting materials for primary and secondary amide, benzamidinate and alkyl complexes of Sc and Y supported by the N₂NN′ ligand. Thus reaction of 1 or 2 with LiN(SiMe₃)₂·Et₂O, LiNMe₂ or LiNHR (R = ^tBu or Ar, where Ar = 2,6-C₆H₃ ⁱPr₂) gave the corresponding five-coordinate amide derivatives [M(NRR″)(N₂NN′)] (M = Sc, R = R″ = SiMe₃4 or Me 6, or R = H, R″ = ^tBu 8 or Ar 9; M = Y, R = R″ = SiMe₃5, or R = H, R″ = Ar 10). The crystal structure of 5 is described. The σ-bond metathesis reaction of [Sc(NMe₂)(N₂NN′)] 6 with Ar_FNH₂ (Ar_F = C₆F₅) gave the corresponding primary flurophenylamide derivative 7. The reaction of 1 or 2 with Li[PhC(NSiMe₃)₂] gave the fluxional, six-coordinate benzamidinate derivatives [M{PhC(NSiMe₃)₂}(N₂NN′)] (M = Sc 11 or Y 12), the crystal structures of which are reported. Finally, reaction of 1 with LiCH₂SiMe₃ formed the alkyl derivative [Sc(CH₂SiMe₃)(N₂NN′)] 13 in reasonable yield; the crystal structure of 13 is described.