Propene asymmetry

The energetically preferred direction of the asynchronous CCI2 addition transition state with propene (20) places the carbene s a orbital closer to Cl, and the substituents on the carbene directed toward The asymmetry of bonding to... 

Addition of hydride to [i7 -C5H5Mo(CO)(NO)-i7 -C3H5]PF6 provides the propene molybdenum analog (6) however, Faller and Rosan (57, 60) have found that hydride addition via cyanoborohydride is stereospecific and produces only one of the pairs of diastereoisomers. The asymmetry in charge induced by the difference in electronic demands of CO and NO appear to provide the driving force for this asymmetric induction. This is a particularly important observation because it represents an electronic control of induction, whereas the usual approach has been to utilize steric effects to promote asymmetric induction (88). The importance of the electronic asymmetry is dramatically demonstrated by perturbations of the endo-exo equilibrium in the molybdenum complexes (60). In this instance there are clearly disparate trans effects of the NO and CO. 

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