Synthesis and NHC Lability of d⁰ Lithium, Yttrium, Titanium, and Zirconium Amido Bis(N-heterocyclic carbene) Complexes

The synthesis of lithium(I) complexes of the neutral and anionic salts of a tridentate aminobis(N-heterocyclic carbene) ligand, L, are reported (L = N{CH2CH2(1-C[NCHCHNMes])}2), along with the X-ray diffraction determined molecular structure of the imidazolium proligand [H2N{CH2CH2(1-HC[NCHCHNMes])}2][Br]3 (H4LBr3). The transamination reaction between the lithium chloride adduct of HL and Y[N{SiMe3}2]3 affords yttrium amidocarbene complexes, while the transamination reaction between the imidazolium proligand and Ti(NMe2)4 or Zr(NMe2)4 affords a titanium or zirconium amidocarbene complex, respectively. The molecular structure of one of the yttrium products, Y(L)(N{SiMe3}2)Cl, is reported. The reactivity of a selection of the complexes with phosphine oxides is compared.