The Molecular Structure of Bromo(ethyl)[(−)-sparteine]magnesium(II), a Catalyst for the Asymmetric-selective Polymerization of Racemic Methacrylates

Abstract
The molecular structure of EtMgBr-(−)-sparteine, which initiates asymmetric (enantiomer) selective polymerization of racemic methacrylates, has been determined by means of X-ray diffraction. The crystal is orthorhombic, space group P212121, a=11.278(2), b=14.112(3), c=11.746(2) Å, Z=4. The structure was established by the heavy atom method and refined by the block-diagonal least-squares procedure: R=0.100 for 1272 non-zero reflections. The Mg atom is tetrahedrally coordinated by the Et group, Br and two N atoms of the (−)-sparteine.