STEREOSPECIFICITY IN REACTIONS OF ACTIVATED ETA-3-ALLYL COMPLEXES OF MOLYBDENUM

Nucleophilic attacks on endo and exo η3-allyl complexes, such as (η5-C5H5)Mo(CO)(NO)(l, 3-dimethylallyl)+ cation, are stereospecific. The structures of the olefinic derivatives formed by the addition of the nucleophile are consistent with nucleophilic attack trans to NO in the endo isomer and cis to NO in the exo isomer. The relative configuration of the newly formed chiral center implies that the attack occurs on the face of the allyl opposite to the metal and not directly at the metal center. The crystal structure determinations of two neutral olefin derivatives, (η5-C5H5)Mo(CO)(NO)(η52-C8H140) and (η5-C5H5)Mo(CO)(NO)(η2-C9H|60), formed by addition of the enamine of isobutyraldéhyde are reported. The olefinic bond tends to be aligned parallel to the molybdenum-carbonyl vector rather than parallel to the η5-C5H5 plane. This orientational preference, which can readily be rationalized by back-bonding arguments, appears to have a profound effect on the selectivity of the reactions. © 1979, American Chemical Society. All rights reserved.