Synthesis, structure, and reactivity of (pentamethylcyclopentadienyl)rhenium aldehyde complexes [(.eta.5-C5Me5)Re(NO)(PPh3)(.eta.2-O:CHR)]+ BF4-: highly diastereoselective deuteride additions
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Reactions of the dichloromethane complex [(η5-C5Me5)Re(NO)(PPh3)(ClCH2Cl)]+BF4- and RCH=O (R; a, CH3; b, CH2CH3; c, CH(CH3)2; d, C6H5; e, CH2C6H5) give π-aldehyde complexes (RS,SR)-[(η5- C5Me5Re(NO)(PPh3)(η2-O=CHR)]+BF4- ((RS,SR)-5a-e, 85-89%). A crystal structure of [RS,SR)-5b shows the RCH=O carbon to be anti to the PPh3 ligand and the ethyl group to be syn to the NO ligand, confirming the stereochemical assignment. The C-O bond length (1.325 (7) Å) is intermediate between that of a single and double bond. Reactions of (RS,SR)-5a-e and formyl complex (η5-C5H5)Re(NO)(PPh3)(CHO) (6) give alkoxide complexes (η5-C5Me5)Re(NO)(PPh3)(OCH2R) (7a-e, 79-88%) and [(η5-C5H5)Re(NO)(PPh3)- (CO)]+BF4- (≥94%). Analogous reactions with deuterioformyl complex 6-d1 give 7a-e-d1 as 78-98:22-2 mixtures of RR,SS and RS,SR diastereomers. The mechanism of diastereoselection is analyzed. Complexes 7a-e-d1 epimerize at rhenium at room temperature. © 1992, American Chemical Society. All rights reserved.
author list (cited authors)
Agbossou, F., Ramsden, J. A., Huang, Y. H., Arif, A. M., & Gladysz, J. A.