Heteroleptic ytterbium(ii) complexes supported by a bulky β-diketiminato ligand

Abstract

Heteroleptic β-diketiminatoytterbium(II) complexes [{Yb(L)(μ-I)(thf)}₂] [1: L = {N(Ar*)C(Me)}₂CH = L¹, 2: L = {N(SiMe₃)C(Ph)}₂CH = L²; Ar* = C₆H₃ⁱPr₂-2,6] were prepared by a salt elimination [from YbI₂(thf)₂ and KL] or by a ligand redistribution [from YbI₂(thf)₂ and YbL₂] reaction. Complexes 1 and 2 were convenient precursors to some new Yb(II) heteroleptic compounds. Thus, reaction of 1 and 2 with KN(SiMe₃)₂ yielded the mononuclear amido compounds [Yb(L){N(SiMe₃)₂}(thf)] (3: L = L¹ and 4: L = L²). Similarly, 1 with K{N(H)Ar*} gave [Yb(L¹){N(H)Ar*}(thf)] (5). Complex 3 was also obtained via a protolytic reaction of [Yb{N(SiMe₃)₂}₂(thf)₂] with HL¹ at an elevated temperature. Treatment of 1 with slightly less than a stoichiometric amount of K{CH(SiMe₃)₂} afforded [Yb(L¹){CH(SiMe₃)₂}(thf)] (6), while using even a small excess of the alkyl reagent resulted in the deprotonation of the β-diketiminato ligand and the formation of the known dimer [{Yb(L³)(thf)}₂] [7, L³ = (Ar*)C(Me)C(H)C(H₂)N(Ar*)]. Compounds 1 or 2 reacted with KCPh₃ in thf yielding [Yb(L¹){η⁵-C₆H₅CPh₂}(thf)] (8) or [Yb(CPh₃)₂(thf)₂] (9), respectively; the latter has two differently coordinated CPh₃ ligands. The molecular structures of 1, 2, 4, 5, 6, 8 and 9 were determined by X-ray diffraction.