Synthesis, structure, and reactions of chiral rhenium vinylidene and acetylide complexes of the formula [(.eta.5-C5H5)Re(NO)(PPh3)(X)]n+. Vinylidene complexes that are formed by stereospecific C.beta. electrophilic attack, exist as two Re=C=C geometric isomers, and undergo stereospecific C.alpha. nucleophilic attack

Abstract

In this paper, the authors report (a) high-yield syntheses of chiral rhenium vinylidene complexes ((/eta//sup 5/-C/sub 5/H/sub 5/)Re(NO)(PPh/sub 3/)(/emdash/C/emdash/CRR/prime/))/sup +/X/sup /minus// and acetylide complexes (/eta//sup 5/-C/sub 5/H/sub 5/)Re(NO)(PPh/sub 3/)(C/identical to/CR), (b) the first observation of M/emdash/C/emdash/C geometric isomerism in vinylidene complexes, (c) the thermal and photochemical interconversion of these geometric isomers and the corresponding rates and activation parameters, (d) examples of stereospecific C/sub /alpha// nucleophilic attack upon the vinylidene complexes and stereospecific C/sub /beta// electrophilic attack upon the acetylide complexes, and (e) X-ray crystal structures that establish the stereochemistry of these transformations and bonding features of both types of complexes. A portion of this study has been communicated.