Structural Studies of Asymmetric Hydrogenation. V. The Crystal Structures of [(S)-1-Cyanoethyl][(S)(−)-α-methylbenzylamine]bis(dimethylglyoximato)cobalt(III) at 293 K and 173 K

Abstract
The structure of [(S)-1-cyanoethyl][(S)(−)-α-methylbenzylamine]bis(dimethylglyoximato)cobalt(III) has been determined by X-ray analysis at 293 K and 173 K. The crystal is monoclinic, the space group being P21, Z=2, with a=8.768(2), b=13.356(2), c=9.538(3) Å, and β=96.73(3)° at 293 K, and a=8.617(4), b=13.222(4), c=9.517(7) Å, and β=96.26(7)° at 173 K. The structure was deduced by the heavy-atom method and was refined by the block-diagonal least-squares method to the final R values of 0.051 and 0.060 for 1878 and 1848 observed reflections at 293 K and 173 K respectively. The bis(dimethylglyoximato)cobalt moiety is twisted in the opposite way from that of [(R)-1-cyanoethyl][(S)(−)-α-methylbenzylamine]bis(dimethylglyoximato)cobalt(III). This supports the proposal that the asymmetry of the optically active amine is transferred into the substrate through the twist of the bis(dimethylglyoximato) cobalt moiety in the step of the σ-bond formation.