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=CMe(2)(CH(2)Me)) 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 CH(2) 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.