Nuclear magnetic resonance studies on partially deuteriated transition metal–methyl derivatives

Abstract

Nuclear magnetic resonance studies on [W(η-C₅Me₄Et)(CH₂D)₄][PF₆] show a strong temperature dependence of the isotope shift [δ(CH₃)–δ(CH₂D)] indicating the presence of a monoagostic methyl group. The magnitude and sign of the geminal coupling constant ²J(H–D)[and ²J(H–H)] and the isotope shift, together with the temperature dependence of this shift, have been recorded for [Ti(CH₂D)Cl₃], [Ti(CH₂D)Cl₃(dmpe)](dmpe = Me₂PCH₂CH₂PMe₂), [Ta(CH₂D)_nCl_5–n](n= 1–3), [M(η-C₅H₅)₂(CH₂D)₂](M = Ti, Zr or Hf), [M(η-C₅H₅)₂(CH₂D)(thf)][BPh₄](M = Ti or Zr, thf = tetrahydrofuran), [Ti(η-C₅H₅)₂(CH₂D)F], [Zr(η-C₅H₅)₂(CH₂D)(MeCN)₂][BPh₄], [Ti(η-C₅H₅)(CH₂D)₃], [M(η-C₅Me₄Et)(CH₂D)₃](M = Ti, Zr or Hf) and [Y(η-C₅Me₅)₂(CH₂D)(thf)]. The isotope shifts for all these complexes are essentially temperature independent. A convenient synthesis of Li(CH₂D) is described.