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.