CLEAVAGE OF THE RHENIUM METHYL BOND OF (ETA-C5H5)RE(NO)(PPH3)(CH3) BY PROTIC AND HALOGEN ELECTROPHILES - STEREOCHEMISTRY AT RHENIUM
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Reaction of (+)-(S)-(-C5H5)Re(NO)(PPh3)(CH3) ((+)-(S)-l) with HX gives (+)-(-C5H5)Re(NO)(PPh3)(X)(X = Cl, (+)-(S)-2; X = Br, (+)-(R)-3; X = I, (+)-(R)-4; X = OSO2CF3, (+)-(R)-5; X = OCOCF3, (+)-(R)-6; X = OCHO, (+)-(R)-7; X = OSO2-p-C6H4CH3, (+)-(R)-8) in 63-85% yields and 99% retention of configuration at rhenium. The corresponding reactions of ()-l give ()-2-()-8 (69-89%). Triflate (+)-(R)-5 and halides (+)-(S)-2 and (+)-(R)-3 are configurationally and chemically less stable than the other cleavage products. Reactions of (-)-(S)-CH3CH2CH(C6H5)CN with (+)-(R)-5, (+)-(S)-2/AgPF6, (+)-(/R)-3/AgPF6, and (+)-(R)-4/AgPF6 give (+)-(SS)-[(-C5H5)Re(NO)(PPh3)-(NCCH(C6H5)CH2CH3)]+X- ((+)-(SS)-9+X-) of 99% diastereomeric purity. Reaction of (+)-(R)-7 with (CH3)3SiCl gives HC02Si(CH3)3 and (+)-(S)-2 in 98% ee. Reaction of (+)-(R)-5 with CO (2000 psi) gives (+)-(S)-[(-C5H5)Re-(NO)(PPh3)(CO)]+CF3SO3- in 78% ee. Reaction of (+)-(5)-l with Cl2, Br2, and I2 gives essentially racemic 2, 3, and 4, respectively. The mechanisms of these reactions, and absolute configuration assignments, are discussed. Products 2-8 are characterized by microanalysis and NMR, IR, mass, UV, ORD, and CD spectroscopy. 1984, American Chemical Society. All rights reserved.
