Synthesis, structure, and alkylation of chiral vinylrhenium complexes (.eta.5-C5H5)Re(NO)(PPh3)(CX:CHR) (X = H, OCH3). A mechanistic study of 1,3-asymmetric induction from rhenium to carbon Academic Article uri icon

abstract

  • Reaction of alkylidene complexes [(775-C5H5)Re(NO)(PPh3)(=CHCH2R)]+PF6(1-PF6_; a, R = H; b, R = CH3; c, R = CH2CH2CH3; d, R = CH2C6H5) with DBU or f-BuO~K+gives vinyl complexes (£')-(r?5-C5H5)Re(NO)(PPh3)(CH=CHR) ((£)-2a-d ; 72-86%). Complexes (£)-2b-d equilibrate to 84—92:16—8 E/Z mixtures in solution. Complex (£)-2b reacts with CF3SO3H and CH30S02F to give ethylidene complex lb-CF3SOf and isobutylidene complex [(r?5-C5H5)Re(NO)(PPh3)-(=CHCH(CH3)2)]+FS03-(3-FSOf; ca. 65%) and with CF3S03D and CD30S02F to give mainly (SR,RS)-\\\\-^d-CF3SOf and (SS,#/?H(775-C5H5)Re(N0)(PPh3)(=CHCH(CH3)(CD3))]+FS03“ However, experimental problems hinder quantification of the 1,3-asymmetric induction. Reaction of 3-FS03-and ?-BuO“K+gives isobutenyl complex (775-C5H5)Re(NO)(PPh3)-(CH=C(CH3)2) (4, 60% from 2b), which in turn reacts with CH30S02F to give neopentylidene complex [(775-C5H5)Re-(N0)(PPh3)(=CH(CH3)3)]+FS03“ (90%). Complex 2a and Ph3C+PF6“ react to give alkylidene complex [(i75-C5H5)Re-(NO)(PPh3)(—CHCH2CPh3)]+PF6“ (81%), which in turn reacts with r-BuO~K+to give vinyl complex (£)-(ij5-C5H5)Re-(NO)(PPh3)(CH—CHCPh3) (74%). Reactions of methoxycarbene complexes [(7j5-C5H5)Re(NO)(PPh3)(=C(OCH3)-CH2R)]+PF6“ with NaH or DBU give a-methoxyvinyl complexes (2)-(7?5-C5H5)Re(NO)(PPh3)(C(OCH3)=CHR) ((Z)-10a,b,d,e (R = C6H5)) in high yields. These are more nucleophilic than (£')-2a-d and react with alkyl iodides RT to give methoxycarbene complexes [(7j5-C5H5)Re(NO)(PPh3)(=C(OCH3)CHRR')]+I-that readily demethylate to acyl complexes (775-C5H5)Re-(NO)(PPh3)(COCHRR0. Thus, (Z)-10b and C6H5CH2Br react to give (5^,^5)-(7?s-C5H5)Re(NO)(PPh3)(COCH-(CH3)(CH2C6H5)) ((SR,RS)-13; 71%), and (Z)-10d and CH31 react to give (SS,RR)A3 (88%; both diastereomers of >98% purity). Crystal structures of (£)-2d and (Z)-10d and extended Hiickel MO calculations on Re-Carotamers of (77s-C5H5)Re(NO)(PH3)(CX=CH2) (X = H, OH) are also described. Data are consistent with the following model for 1,3-asymmetric induction: electrophiles attack a Re-Carotamer with the ON-Re-C^-C^ torsion angle (6) close to 0° and on the C=C face opposite the bulky PPh3ligand. © 1987, American Chemical Society. All rights reserved.

author list (cited authors)

  • Bodner, G. S., Smith, D. E., Hatton, W. G., Heah, P. C., Georgiou, S., Rheingold, A. L., ... Gladysz, J. A.

citation count

  • 42
  • 48

publication date

  • December 1987