Synthesis and Coordination Chemistry of Pentadienyl Ligands Derived from (1<i>R</i>)‑(−)-Myrtenal

Abstract

With the natural product (1<i>R</i>)-(−)-myrtenal as the starting material, a series of chiral pentadienes (Pdl*) such as dimethylnopadiene (<b>2a</b>), methylphenylnopadiene (<b>2b</b>), and methylnopadiene (<b>2c</b>) have been prepared by Wittig reactions. Deprotonation with the Schlosser base gives the corresponding potassium pentadienides <b>3a-K</b>–<b>3c-K</b>, whose structures were investigated by NMR spectroscopy and X-ray diffraction studies. In all cases a “U” conformation was observed. Furthermore, the coordination chemistry and electronic properties of these new pentadienyl systems were explored in several half-open trozircene complexes [(η⁷-C₇H₇)­Zr­(η⁵-Pdl*)] and their PMe₃ and <i>t</i>BuNC adducts. Density functional theory (DFT) computations are consistent with the experimentally observed face selectivity upon metal coordination: namely, that the metal coordinates exclusively from the sterically less encumbered side