Synthesis, fluxional behaviour in solution and crystal structure of the organolanthanide complexes [Ln(C5H4CH2CH2OMe)2(thf)][Co(CO)4](Ln = Sm or Yb, thf = tetrahydrofuran)

Abstract

The [Ln(C₅H₄CH₂CH₂OMe)₂(thf)]⁺ cations (Ln = Sm 1 or Yb 2, thf = tetrahydrofuran) which represent the first examples of organolanthanide cationic complexes with [Co(CO)₄]_– as anion, have been synthesised by metathesis of [Ln(C₅H₄CH₂CH₂OMe)₂I] with K[Co(CO)₄] or by one-electron oxidation of divalent [Ln(C₅H₄CH₂CH₂OMe)₂(thf)] with [Co₂(CO)₈]. The crystal structure of complex 2 has been determined: space group P2₁2₁2, a= 10.700(3), b= 11.509(4), c= 10.381(4)Å, Z= 2. Least-squares refinement led to convergence with R= 0.040, R′= 0.047. It exists as discrete cations and anions with no Ln–OC–Co linkage. The samarium analogue 1 is isostructural. Variable-temperature NMR studies indicated that, at low temperature, the spectra of complex 1 are in good accordance with the structure in the solid state. At high temperature the two ether chains of 2 remain co-ordinated on the metal.