Enantiomerically Pure Constrained Geometry Complexes Of The Rare-Earth Metals Featuring A Dianionic N-Donor Functionalised Pentadienyl Ligand: Synthesis And Characterisation

We report the preparation of enantiomerically pure constrained geometry complexes (cgc) of the rare-earth metals bearing a pentadienyl moiety (pdl) derived from the natural product (1R)-(-)-myrtenal. The potassium salt 1, [Kpdl*], was treated with ClSiMe(2)NHtBu, and the resulting pentadiene 2 was deprotonated with the Schlosser-type base KOtPen/nBuLi (tPen=CMe2(CH2Me)) to yield the dipotassium salt [K-2(pdl*SiMe(2)NtBu)] (3). However, 3 rearranges in THF solution to its isomer 3' by a 1,3-H shift, which elongates the bridge between the pdl and SiMe(2)NtBu moieties by one CH2 unit. This is crucial for the successful formation of various monomeric C-1- or dimeric C-2-symmetric rare-earth cgc complexes with additional halide, tetraborohydride, amido and alkyl functionalities. All compounds have been extensively characterised by solid-state X-ray diffraction analysis, solution NMR spectroscopy and elemental analyses.